Measurement of D-meson production at mid-rapidity in pp collisions at $\mathbf{\sqrt{s}=7}$ TeV

TL;DR

This paper reports precise measurements of D-meson production cross sections at mid-rapidity in proton-proton collisions at 7 TeV, extending the transverse momentum coverage and reducing uncertainties, and compares results with perturbative QCD predictions.

Contribution

The study provides improved and extended measurements of D-meson production cross sections at 7 TeV, with reduced uncertainties and better comparison with theoretical models.

Findings

Extended pT coverage in D-meson measurements.

Reduced uncertainties in cross section measurements.

Better agreement with perturbative QCD calculations.

Abstract

The production cross sections of the prompt charmed mesons ${\rm D^0}$, ${\rm D^+}$, ${\rm D^{*+}}$ and ${\rm D_s^+}$ were measured at mid-rapidity in proton-proton collisions at a centre-of-mass energy $\sqrt{s}=7$ TeV with the ALICE detector at the Large Hadron Collider (LHC). D mesons were reconstructed from their decays ${\rm D}^0 \to {\rm K}^-\pi^+$, ${\rm D}^+\to {\rm K}^-\pi^+\pi^+$, ${\rm D}^{*+} \to {\rm D}^0 \pi^+$, ${\rm D_s^{+}\to \phi\pi^+\to K^-K^+\pi^+}$, and their charge conjugates. With respect to previous measurements in the same rapidity region, the coverage in transverse momentum ($p_{\rm T}$) is extended and the uncertainties are reduced by a factor of about two. The accuracy on the estimated total $\rm c\overline c$ production cross section is likewise improved. The measured $p_{\rm T}$-differential cross sections are compared with the results of three perturbative QCD calculations.

Figures

Tables

Table 1. Table 1: Summary of relative systematic uncertainties for two p T subscript 𝑝 T p_{\rm T} intervals.

	$D^0$		$D^{+}$		$D^{\ast +}$		$D_s^{+}$
$p_T$ (GeV/$c$)	2–3	10–12	2–3	10–12	2–3	10–12	2–4	8–12
Signal yield	3%	4%	6%	5%	2%	2%	5%	5%
Tracking efficiency	4%	4%	4%	6%	6%	6%	5%	6%
Selection efficiency	5%	5%	10%	5%	5%	5%	7%	7%
PID efficiency	0	0	0	0	0	0	7%	7%
$p_T$ shape in MC	0	0	1%	2%	2%	0	3%	2%
Feed-down	${}_{-4}{}^{+4}\%$	${}_{-5}{}^{+3}\%$	${}_{-3}{}^{+2}\%$	${}_{-3}{}^{+2}\%$	${}_{-2}{}^{+2}\%$	${}_{-3}{}^{+2}\%$	${}_{-5}{}^{+4}\%$	${}_{-5}{}^{+4}\%$
Branching ratio	1.0%		2.5%		1.3%		3.5%
Normalisation	3.5%

Table 2. Table 2: Visible production cross sections of prompt D mesons in | y | < 0.5 𝑦 0.5 |y|<0.5 in pp collisions at s = 7 ​ TeV 𝑠 7 TeV \sqrt{s}=7\leavevmode\nobreak\ \mathrm{TeV} .

	Kinematic range	Visible cross section ($\mu b$)
$D^0$		$500\pm 36\left(\mathrm{stat}\right)\pm 39\left(\mathrm{syst}\right)\pm 18\left(\mathrm{lumi}\right)\pm 5\left(\mathrm{BR}\right)$
		$402\pm 24\left(\mathrm{stat}\right)\pm 28\left(\mathrm{syst}\right)\pm 14\left(\mathrm{lumi}\right)\pm 4\left(\mathrm{BR}\right)$
		$210\pm 7\left(\mathrm{stat}\right)\pm 14\left(\mathrm{syst}\right)\pm 7\left(\mathrm{lumi}\right)\pm 2\left(\mathrm{BR}\right)$
$D^{+}$		$182\pm 14\left(\mathrm{stat}\right)\pm 20\left(\mathrm{syst}\right)\pm 6\left(\mathrm{lumi}\right)\pm 5\left(\mathrm{BR}\right)$
		$89\pm 3\left(\mathrm{stat}\right)\pm 9\left(\mathrm{syst}\right)\pm 3\left(\mathrm{lumi}\right)\pm 2\left(\mathrm{BR}\right)$
$D^{\ast +}$		$207\pm 24\left(\mathrm{stat}\right)\pm 20\left(\mathrm{syst}\right)\pm 7\left(\mathrm{lumi}\right)\pm 3\left(\mathrm{BR}\right)$
		$101\pm 6\left(\mathrm{stat}\right)\pm 8\left(\mathrm{syst}\right)\pm 4\left(\mathrm{lumi}\right)\pm 1\left(\mathrm{BR}\right)$
$D_s^{+}$		$40\pm 8\left(\mathrm{stat}\right)\pm 5\left(\mathrm{syst}\right)\pm 1\left(\mathrm{lumi}\right)\pm 1\left(\mathrm{BR}\right)$

Table 3. Table 3: Ratios of the measured p T subscript 𝑝 T p_{\rm T} -integrated cross sections of prompt D mesons in | y | < 0.5 𝑦 0.5 |y|<0.5 in pp collisions at s = 7 ​ TeV 𝑠 7 TeV \sqrt{s}=7\leavevmode\nobreak\ \mathrm{TeV} .

	Kinematic range	Production cross section ratio
$\sigma \left(D^{+}\right)/\sigma \left(D^0\right)$		$0.45\pm 0.04\left(\mathrm{stat}\right)\pm 0.05\left(\mathrm{syst}\right)\pm 0.01\left(\mathrm{BR}\right)$
$\sigma \left(D^{\ast +}\right)/\sigma \left(D^0\right)$		$0.52\pm 0.07\left(\mathrm{stat}\right)\pm 0.05\left(\mathrm{syst}\right)\pm 0.01\left(\mathrm{BR}\right)$
$\sigma \left(D_s^{+}\right)/\sigma \left(D^0\right)$		$0.19\pm 0.04\left(\mathrm{stat}\right)\pm 0.02\left(\mathrm{syst}\right)\pm 0.01\left(\mathrm{BR}\right)$
$\sigma \left(D_s^{+}\right)/\sigma \left(D^{+}\right)$		$0.45\pm 0.09\left(\mathrm{stat}\right)\pm 0.06\left(\mathrm{syst}\right)\pm 0.02\left(\mathrm{BR}\right)$

Table 4. Table 4: Production cross sections of prompt D mesons in | y | < 0.5 𝑦 0.5 |y|<0.5 and full p T subscript 𝑝 T p_{\rm T} range in pp collisions at s = 7 ​ TeV 𝑠 7 TeV \sqrt{s}=7\leavevmode\nobreak\ \mathrm{TeV} .

	Extr. factor to $p_T>0$	($\mu b$)
$D^0$	${1.0002}_{-0.0002}^{+0.0004}$	$500\pm 36\left(\mathrm{stat}\right)\pm 39\left(\mathrm{syst}\right)\pm 18\left(\mathrm{lumi}\right)\pm 5\left(\mathrm{BR}\right)$
$D^{+}$	${1.25}_{-0.09}^{+0.29}$	$227\pm 18\left(\mathrm{stat}\right)\pm 25\left(\mathrm{syst}\right)\pm 8\left(\mathrm{lumi}\right)\pm 6{\left(\mathrm{BR}\right)}_{-16}^{+52}\left(\mathrm{extrap}\right)$
$D^{\ast +}$	${1.21}_{-0.08}^{+0.28}$	$251\pm 29\left(\mathrm{stat}\right)\pm 24\left(\mathrm{syst}\right)\pm 9\left(\mathrm{lumi}\right)\pm 3{\left(\mathrm{BR}\right)}_{-16}^{+58}\left(\mathrm{extrap}\right)$
$D_s^{+}$	${2.23}_{-0.65}^{+0.71}$	$89\pm 18\left(\mathrm{stat}\right)\pm 11\left(\mathrm{syst}\right)\pm 3\left(\mathrm{lumi}\right)\pm 3{\left(\mathrm{BR}\right)}_{-26}^{+28}\left(\mathrm{extrap}\right)$

Equations

$$\frac{{\mathrm{d}}^2{\sigma }^{\mathrm{D}}}{\mathrm{d}{p}_{\mathrm{T}}\mathrm{d}y}=\frac{1}{c_{\Delta y}\text{leavevmode}\Delta p_{\mathrm{T}}}\frac{1}{\mathrm{BR}}\frac{\frac{1}{2}{f_{\mathrm{prompt}}\cdot N^{\mathrm{D}+\overline{\mathrm{D}},\mathrm{raw}}|}_{|y|<y_{\mathrm{fid}}}}{(\mathrm{Acc}\times ϵ{)}_{\mathrm{prompt}}}\frac{1}{L_{\mathrm{int}}},$$

$$f_{\mathrm{prompt}}=1-\frac{N_{\mathrm{raw}}^{\text{Dleavevmodenobreak feed-down}}}{N_{\mathrm{raw}}^{\mathrm{D}}}=1-{\left(\frac{{\mathrm{d}}^2\sigma }{\mathrm{d}{p}_{\mathrm{T}}\mathrm{d}y}\right)}_{\text{feed-down}}^{\mathrm{FONLL}}\cdot \frac{(\mathrm{Acc}\times ϵ{)}_{\text{feed-down}}\cdot \Delta y\Delta p_{\mathrm{T}}\cdot \mathrm{BR}\cdot L_{\mathrm{int}}}{N^{\mathrm{D}+\overline{\mathrm{D}},\mathrm{raw}}/2},$$

$$f(p_{\mathrm{T}})=C\frac{p_{\mathrm{T}}}{(1+(p_{\mathrm{T}}/p_0{)}^2{)}^n},$$

$${⟨p_{\mathrm{T}}⟩}_{\mathrm{pp},7\mathrm{TeV}}^{\mathrm{prompt}{\mathrm{D}}^0}=2.19\pm 0.06(stat.)\pm 0.04(syst.)\text{leavevmode}\mathrm{GeV}/c.$$

$${\mathrm{d}{\sigma }_{\mathrm{pp},7\mathrm{TeV}}^{\mathrm{c}\overline{\mathrm{c}}}/\mathrm{d}y|}_{|y|<0.5}=954\pm 69(\mathrm{stat})\pm 74(\mathrm{syst})\pm 33(\mathrm{lumi})\pm 42(\mathrm{FF})\pm 31(rap.shape)\text{leavevmode}\mu \mathrm{b}.$$

$${\sigma }_{\mathrm{pp},7\mathrm{TeV}}^{\mathrm{prompt}{\mathrm{D}}^0}=4.28\pm 0.31(\mathrm{stat})\pm 0.33(\mathrm{syst}){}_{-0.24}^{+1.26}(extr.)\pm 0.15(\mathrm{lumi})\pm 0.04(\mathrm{BR})\text{leavevmode}\mathrm{mb}.$$

$${\sigma }_{\mathrm{pp},7\mathrm{TeV}}^{\mathrm{c}\overline{\mathrm{c}}}(\mathrm{ALICE})=7.89\pm 0.57(stat.)\pm 0.61(syst.){}_{-0.45}^{+2.32}(extr.)\pm 0.28(lumi.)\pm 0.35(\mathrm{FF})\text{leavevmode}\mathrm{mb},$$

$${\sigma }_{\mathrm{pp},7\mathrm{TeV}}^{\mathrm{c}\overline{\mathrm{c}}}(\mathrm{ALICE},\mathrm{LHCb})=7.44\pm 0.14(stat.)\pm 0.46(syst.){}_{-0.07}^{+0.13}(extr.)\pm 0.33(\mathrm{FF})\text{leavevmode}\mathrm{mb},$$

$${\mathrm{d}{\sigma }_{\mathrm{pp},7\mathrm{TeV}}^{\mathrm{c}\overline{\mathrm{c}}}/\mathrm{d}y|}_{|y|<0.5}=954\pm 69(\mathrm{stat})\pm 97(tot.\text{leavevmode}syst.)\text{leavevmode}\mu \mathrm{b}.$$

$${\sigma }_{\mathrm{pp},7\mathrm{TeV}}^{\mathrm{c}\overline{\mathrm{c}}}(\mathrm{ALICE},\mathrm{LHCb})=7.44\pm 0.14(stat.)\pm 0.58(tot.\text{leavevmode}syst.)\text{leavevmode}\mathrm{mb}.$$

Full text

\PHyear2017 \PHnumber020 \PHdate30 January

\ShortTitleD-meson production in pp collisions at $\sqrt{s}=7$ TeV

\CollaborationALICE Collaboration††thanks: See Appendix A for the list of collaboration members \ShortAuthorALICE Collaboration

The production cross sections for prompt charmed mesons ${\rm D^{0}}$, ${\rm D^{+}}$, ${\rm D^{*+}}$ and ${\rm D_{s}^{+}}$ were measured at mid-rapidity in proton–proton collisions at a centre-of-mass energy $\sqrt{s}=7\leavevmode\nobreak\ \mathrm{TeV}$ with the ALICE detector at the Large Hadron Collider (LHC). D mesons were reconstructed from their decays ${\rm D}^{0}\to{\rm K}^{-}\pi^{+}$, ${\rm D}^{+}\to{\rm K}^{-}\pi^{+}\pi^{+}$, ${\rm D}^{*+}\to{\rm D}^{0}\pi^{+}$, ${\rm D_{s}^{+}\to\phi\pi^{+}\to K^{-}K^{+}\pi^{+}}$, and their charge conjugates. With respect to previous measurements in the same rapidity region, the coverage in transverse momentum ($p_{\rm T}$) is extended and the uncertainties are reduced by a factor of about two. The accuracy on the estimated total $\rm c\overline{c}$ production cross section is likewise improved. The measured $p_{\rm T}$-differential cross sections are compared with the results of three perturbative QCD calculations.

1 Introduction

In high-energy hadronic collisions heavy quarks are produced by hard scatterings between partons of the two incoming hadrons. The production cross section of hadrons with charm or beauty quarks is calculated in the framework of Quantum Chromodynamics (QCD) and factorised as a convolution of the hard scattering cross sections at partonic level, the parton distribution functions (PDFs) of the incoming hadrons and the non-perturbative fragmentation functions of heavy quarks to heavy-flavour hadrons. Factorisation is implemented in terms of the squared momentum transfer $Q^{2}$ (collinear factorisation) [1] or of the partonic transverse momentum $k_{\rm T}$ [2]. The hard scattering cross section is expanded in a perturbative series in powers of the strong coupling constant $\alpha_{\rm s}$. State-of-the-art calculations based on collinear factorisation implement a perturbative expansion up to next-to-leading order (NLO) in $\alpha_{\rm s}$, such as the general-mass variable flavour number scheme (GM-VFNS) [3, 4, 5], or next-to-leading order in $\alpha_{\rm s}$ with all-order resummation of the logarithms of $p_{\rm T}/m_{Q}$ (FONLL) [6, 7], where $p_{\rm T}$ and $m_{Q}$ are the heavy-quark transverse momentum and mass, respectively. Calculations based on $k_{\rm T}$ factorisation exist only at leading order (LO) in $\alpha_{\rm s}$ [8, 9, 2]. All these calculations provide a good description of the production cross sections of D and B mesons in proton–proton (and proton–antiproton) collisions at centre-of-mass energies from 0.2 to 13 TeV over a wide $p_{\rm T}$ range at both central and forward rapidities (see e.g. [10] and references therein). In the case of charm production the uncertainties of the theoretical calculations, dominated by the perturbative scale uncertainties, are significantly larger than the experimental ones [11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21]. However, it was recently pointed out that in ratios of cross sections at different LHC energies and in different rapidity intervals the perturbative uncertainty becomes subdominant with respect to the uncertainty on the PDFs [22], thus making the measurement sensitive in particular to the gluon PDF at values of Bjorken-$x$ down to $10^{-5}$ when the D-meson $p_{\rm T}$ approaches 0. This represents a strong motivation for pursuing precise measurements of D-meson production in pp collisions at LHC energies. Charm hadroproduction measurements are also required for cosmic-ray and neutrino astrophysics, where high-energy neutrinos from the decay of charmed hadrons produced in particle showers in the atmosphere constitute an important background for neutrinos from astrophysical sources [23, 24, 25, 26].

In the context of the heavy-ion programme at the LHC, D-meson measurements in pp collisions represent an essential reference for the study of effects induced by cold and hot strongly-interacting matter in the case of proton–nucleus and nucleus–nucleus collisions (see e.g. the recent reviews [10, 27]). In addition, the $\rm c\overline{c}$ production cross section per nucleon–nucleon collision is a basic ingredient for the determination of the amount of charmonium production by (re)generation in a quark-gluon plasma [28, 29, 30], a mechanism that is supported by $\rm J/\psi$ measurements in nucleus–nucleus collisions at the LHC [31, 32]. A precise measurement of the $\rm c\overline{c}$ production cross section in pp collisions would enable a more stringent comparison of model calculations with data.

In this article, we report the measurement of the production cross sections of prompt $\rm D^{0}$, $\rm D^{+}$, $\rm D^{*+}$ and $\rm D_{s}^{+}$ mesons (as average of particles and anti-particles), and of their ratios, in pp collisions at the centre-of-mass energy $\sqrt{s}=7\leavevmode\nobreak\ \mathrm{TeV}$ using the ALICE detector at the LHC. The measurements cover mid-rapidity ($|y|<0.5$) and the intervals $0<p_{\rm T}<36\leavevmode\nobreak\ \mathrm{GeV}/c$ for $\rm D^{0}$ mesons, $1<p_{\rm T}<24\leavevmode\nobreak\ \mathrm{GeV}/c$ for $\rm D^{+}$ and $\rm D^{*+}$mesons, and $2<p_{\rm T}<12\leavevmode\nobreak\ \mathrm{GeV}/c$ for $\rm D^{+}_{s}$ mesons. The measurements cover complementary intervals in $p_{\rm T}$ and rapidity with respect to those published by the ATLAS ($3.5<p_{\rm T}<100\leavevmode\nobreak\ \mathrm{GeV}/c$, $|\eta|<2.1$ [13]) and LHCb ($0<p_{\rm T}<8\leavevmode\nobreak\ \mathrm{GeV}/c$, $2<y<4.5$ [19]) Collaborations at the same centre-of-mass energy. In comparison to previous ALICE publications based on the same data sample [14, 16, 17], the present results have a significantly extended $p_{\rm T}$ coverage (for example, the previous coverage for $\rm D^{0}$ mesons was 0–16 $\mathrm{GeV}/c$) and total uncertainties reduced by a factor of about two. These improvements have several sources: i) changes in the detector calibration, alignment and track reconstruction algorithm, which resulted in better $p_{\rm T}$ resolution, thus higher signal-to-background ratio; ii) optimization of the D-meson selection procedure; iii) refinements in the estimation of the systematic uncertainties, which is now more data-driven; iv) a data sample with 20% larger integrated luminosity.

The article is organised as follows: the data sample and the analysis procedure are described in Section 2, the estimation of the systematic uncertainties is discussed in Section 3 and the results are presented and compared to theoretical calculations in Section 4.

2 Analysis

A complete description of the ALICE experimental setup and of its performance can be found in [33, 34]. D mesons were reconstructed at mid-rapidity from their decay products, using the tracking and particle identification capabilities of the ALICE central barrel detectors located within a large solenoidal magnet, providing a field B = $0.5\leavevmode\nobreak\ \mathrm{T}$ parallel to the beam line ($z$ axis of the ALICE reference frame). The innermost detector, the Inner Tracking System (ITS), is used to track charged particles within the pseudorapidity interval $|\eta|<0.9$ as well as for primary and secondary vertex reconstruction. It consists of six cylindrical layers equipped with Silicon Pixel Detectors (SPD), Silicon Drift Detectors (SDD) and Silicon Strip Detectors (SSD) from inner to outer layers. The ITS provides a resolution on the track impact parameter $d_{0}$ to the primary vertex in the transverse plane ($r\varphi$) better than 75 $\mu$m for transverse momentum $p_{\rm T}>1\leavevmode\nobreak\ \mathrm{GeV}/c$. As compared to previous publications based on the same data sample [14, 16], the alignment of the ITS sensor modules was improved and a new procedure for the calibration of the drift velocity and of the non-uniformities of the drift field in the SDD was used. The Time Projection Chamber (TPC) provides track reconstruction as well as particle identification via the measurement of the specific ionisation energy loss d$E$/d$x$. The Time-Of-Flight detector (TOF) extends the charged particle identification capabilities of the TPC via the measurement of the flight time of the particles from the interaction point. The event collision time is measured with the T0 detector, which consists of two arrays of Cherenkov counters located at $+350$ cm and $-70$ cm along the beam line, or, for the events with sufficiently large multiplicity, it is estimated using the particle arrival times at the TOF [35]. The V0 detector, used in the online trigger and offline event selection, consists of two arrays of 32 scintillators each, covering the pseudorapidity intervals $-3.7<\eta<-1.7$ and $2.8<\eta<5.1$, placed around the beam vacuum tube on either side of the interaction region. A minimum-bias (MB) trigger was used to collect the data sample, by requiring at least one hit in either of the V0 counters or in the SPD ($|\eta|<2$). Events were selected off-line by using the timing information from the V0 and the correlation between the number of hits and track segments in the SPD detector to remove background due to beam–gas interactions. Only events with a primary vertex reconstructed within $\pm 10\leavevmode\nobreak\ \rm{cm}$ from the centre of the detector along the beam line were used for the analysis. The analysed data sample consists of about 370 million MB events, corresponding to an integrated luminosity $L_{\rm int}=(6.0\pm 0.2)$ nb*-1*, collected during the 2010 pp run at $\sqrt{s}=7$ TeV.

D mesons were reconstructed via their hadronic decay channels ${\rm D}^{0}\to{\rm K}^{-}\pi^{+}$ (with branching ratio, BR = 3.93 $\pm$ 0.04%), ${\rm D}^{+}\to{\rm K}^{-}\pi^{+}\pi^{+}$ (BR = 9.46 $\pm$ 0.24%), ${\rm D^{*+}(2010)\to D^{0}\pi^{+}}$ (strong decay with BR = 67.7 $\pm$ 0.5%) with ${\rm D}^{0}\to{\rm K}^{-}\pi^{+}$ and ${\rm D_{s}^{+}\to\phi\pi^{+}}$ (BR = 2.27 $\pm$ 0.08%) with ${\rm\phi\to K^{-}K^{+}}$, together with their charge conjugates [36].

D-meson candidates were defined using pairs or triplets of tracks with the proper charge-sign combination. Tracks were required to have $|\eta|<0.8$, $p_{\rm T}>0.3\leavevmode\nobreak\ \mathrm{GeV}/c$, at least 70 associated TPC space points (out of a maximum of 159), $\chi^{2}/{\rm ndf}<2$ in the TPC (where ndf is the number of degrees of freedom involved in the track fit procedure), and at least one hit in either of the two layers of the SPD. For the soft pion produced in ${\rm D^{*+}}$ decay, also tracks reconstructed only with the ITS, with at least four hits, including at least one in the SPD, and $p_{\rm T}>$ 80 $\mathrm{MeV}/c$ were considered. With these track selection criteria, the acceptance in rapidity for D mesons drops steeply to zero for $|y|>0.5$ at low $p_{\rm T}$ and $|y|>0.8$ at $p_{\rm T}>5\leavevmode\nobreak\ \mathrm{GeV}/c$. A $p_{\rm T}$-dependent fiducial acceptance cut was therefore applied on the D-meson rapidity, $|y|<y_{\rm fid}(p_{\rm T})$, with $y_{\mathrm{fid}}(p_{\rm T})$ increasing from 0.5 to 0.8 in the transverse momentum range $0<p_{\rm T}<5\leavevmode\nobreak\ \mathrm{GeV}/c$ according to a second-order polynomial function, and $y_{\mathrm{fid}}=0.8$ for $p_{\rm T}>5\leavevmode\nobreak\ \mathrm{GeV}/c$.

${\rm D^{0}}$, ${\rm D^{+}}$ and ${\rm D_{s}^{+}}$ mesons have mean proper decay lengths $c\tau$ of about 123, 312 and 150 $\mu$m, respectively [36]. Their decay vertices are therefore typically displaced by a few hundred $\mu$m from the primary vertex of the interaction. Geometrical selections on the D-meson decay topology were applied to reduce the combinatorial background. The selection requirements were tuned so as to provide a large statistical significance for the signal and to keep the selection efficiency as high as possible. The latter requirement was dictated also by the fact that too tight cuts result in an increased contribution to the raw yield from feed-down D mesons originating from decays of B mesons. In the ${\rm D}^{*+}\to{\rm D}^{0}\pi^{+}$ case, the decay vertex cannot be resolved from the primary vertex and geometrical selections were applied on the secondary vertex topology of the produced ${\rm D^{0}}$. The geometrical selections were mainly based on the displacement of the tracks from the interaction vertex, the distance between the D-meson decay vertex and the primary vertex (decay length, $L$), and the pointing of the reconstructed D-meson momentum to the primary vertex. The pointing condition is applied by requiring a small value for the angle $\theta_{\rm pointing}$ between the directions of the reconstructed momentum of the candidate and its flight line, defined by the vector from the primary to the secondary vertex. In comparison to the previous analysis of the same data sample, additional selection criteria were introduced. In particular, the projections of the pointing angle and of the decay length in the transverse plane ($\theta_{\rm pointing}^{r\varphi}$ and $L^{r\varphi}$) were considered. Moreover, a cut on the normalised difference between the measured and expected impact parameters of each of the decay particles $(d^{\rm reco}_{0,tr}-d^{\rm exp}_{0,tr}$)/$\sigma_{\Delta}$ was applied, where $d^{\rm reco}_{0,tr}$ is the measured track impact parameter, $d^{\rm exp}_{0,tr}$ is defined as $L^{r\varphi}\sin(\theta_{\rm tr,D}^{r\varphi})$, $\theta_{\rm tr,D}^{r\varphi}$ is the measured angle between the momenta of the D meson and of the considered track, and $\sigma_{\Delta}$ is the combination of the uncertainties on the measured and expected $d_{0}$. By requiring $(d^{\rm reco}_{0,tr}-d^{\rm exp}_{0,tr})/\sigma_{\Delta}<3$, a significant rejection of background candidates (15–40% depending on D-meson species and $p_{\rm T}$) and feed-down D mesons (up to 50% at high $p_{\rm T}$) is achieved while keeping almost 100% of the prompt D mesons.

Further reduction of the combinatorial background was obtained by applying particle identification (PID) to the decay tracks. A $3\sigma$ compatibility cut was applied on the difference between the measured and expected signals for pions and kaons for both the $\mathrm{d}E/\mathrm{d}x$ and time-of-flight. Tracks without TOF hits were identified using only the TPC information with a $3\,\sigma$ selection for ${\rm D^{0}}$, ${\rm D^{+}}$ and ${\rm D^{*+}}$ decay products, and a $2\,\sigma$ selection for the ${\rm D_{s}^{+}}$. This stricter PID selection strategy was needed in the ${\rm D_{s}^{+}}$ case due to the large background of track triplets and the short ${\rm D_{s}^{+}}$ lifetime, which limits the effectiveness of the geometrical selections on the displaced decay-vertex topology. Based on the PID information and the charge sign of the decay tracks, ${\rm D^{0}}$ candidates were accepted (as $\rm{D^{0}}$, $\rm{\overline{D^{0}}}$, or both) or rejected, according to the compatibility with the K*∓*$\pi^{\pm}$ final state. For the ${\rm D^{*+}}$ reconstruction, this ambiguity is resolved using the charge of the soft pion. In the cases of the ${\rm D_{s}^{+}\to K^{-}K^{+}\pi^{+}}$ and ${\rm D}^{+}\to{\rm K}^{-}\pi^{+}\pi^{+}$ decays, a candidate was rejected if the track with charge opposite to that of the D meson was not compatible with the kaon PID hypothesis.

The D-meson raw yields, including both particles and anti-particles, were obtained from fits to the ${\rm D^{0}}$, ${\rm D^{+}}$ and ${\rm D_{s}^{+}}$ candidate invariant-mass distributions and to the mass difference $\Delta M=M(\mathrm{K}\pi\pi)-M(\mathrm{K}\pi)$ distributions for ${\rm D^{*+}}$ candidates. In the fit function, the signal was modeled with a Gaussian and the background was described by an exponential term for ${\rm D^{0}}$, ${\rm D^{+}}$ and ${\rm D_{s}^{+}}$ candidates and by the function $a\sqrt{\Delta M-m_{\pi}}\cdot{\rm e}^{b(\Delta M-m_{\pi})}$ for ${\rm D^{*+}}$ candidates. In the case of ${\rm D^{0}}$ mesons, an additional term was included in the fit function to account for the contribution of signal candidates that are present in the invariant mass distribution with the wrong daughter particle mass assignment (reflections). A study with Monte Carlo simulations showed that about 70$\%$ of these reflections are rejected by the PID selections. The residual contribution was accounted for by including in the fit a template consisting of the sum of two wide Gaussians with centroids and widths fixed to values obtained in the simulation and with amplitudes normalised using the signal observed in data.

Figure 1 shows fits to the invariant-mass (mass-difference) distributions in three $p_{\rm T}$ intervals for ${\rm D^{0}}$, ${\rm D^{+}}$, (${\rm D^{*+}}$) and ${\rm D_{s}^{+}}$ candidates from top to bottom. The mean values of the Gaussians in all transverse-momentum intervals were found to be compatible within uncertainties with the world average rest mass values for ${\rm D^{0}}$, ${\rm D^{+}}$ and ${\rm D_{s}^{+}}$ and with the difference $M_{{\rm D^{*+}}}-M_{{\rm D^{0}}}$ for the ${\rm D^{*+}}$ [36]. The widths are consistent with the results from Monte Carlo simulations and smaller by 10–20% than the values in [14, 16], as a consequence of the improved $p_{\rm T}$ resolution.

The $p_{\rm T}$-differential cross section of prompt D mesons was computed as:

[TABLE]

where $f_{\rm prompt}$, $N^{\rm D+\overline{D},raw}$ and $({\rm Acc}\times\epsilon)_{\rm prompt}$ are $p_{\rm T}$-interval dependent quantities. The raw yield values (sum of particles and antiparticles, $N^{\rm D+\overline{D},raw}$) were corrected for the B-meson decay feed-down contribution (i.e. multiplied by the prompt fraction $f_{\rm{prompt}}$ in the raw yield), divided by the acceptance-times-efficiency for prompt D mesons $(\rm Acc\times\epsilon)_{\rm{prompt}}$, and divided by a factor of two to obtain the particle and antiparticle averaged yields. The $p_{\rm T}$-differential yields for each D-meson species, measured separately for particles and anti-particles, were found to be in agreement within statistical uncertainties. The corrected yields were divided by the decay channel BR, the $p_{\rm T}$ interval width $\Delta p_{\rm T}$, the correction factor for the rapidity coverage $c_{\Delta y}$, and the integrated luminosity $L_{\rm int}=N_{\rm ev}/\sigma_{\rm MB}$, where $N_{\rm ev}$ is the number of analysed events and $\sigma_{\rm MB}=62.2$ mb is the cross section for the MB trigger condition [37].

The $(\rm Acc\times\epsilon)$ correction factor was determined using simulations of pp collisions generated with the PYTHIA 6.4.21 event generator [38] (Perugia-0 tune [39]), and particle transport through the apparatus using GEANT3 [40]. The luminous region distribution and the conditions of all the ALICE detectors were included in the simulations. The $(\rm Acc\times\epsilon)$ for prompt and feed-down ${\rm D^{0}}$, ${\rm D^{+}}$, ${\rm D^{*+}}$ and ${\rm D_{s}^{+}}$ mesons with $|y|<y_{\rm fid}$ is shown in Fig. 2 as a function of $p_{\rm T}$. The efficiencies for feed-down D mesons are higher than those for prompt D mesons in most of the $p_{\rm T}$ intervals, because the decay vertices of the feed-down D mesons are on average more displaced from the primary vertex due to the large B-meson lifetime ($c\tau\approx 500\leavevmode\nobreak\ \mathrm{\mu m}$ [36]). However, the selection on the difference between measured and expected decay-track impact parameters rejects more efficiently feed-down D mesons, thus reducing the difference between prompt and feed-down efficiencies as compared to the previous analyses.

The rapidity acceptance correction factor $c_{\Delta y}$ was computed with the PYTHIA 6.4.21 event generator with Perugia-0 tune as the ratio between the generated D-meson yield in $\Delta y=2\,y_{\rm fid}$, (with $y_{\rm fid}$ varying from 0.5 at low $p_{\rm T}$ to 0.8 at high $p_{\rm T}$) and that in $|y|<0.5$. It was checked that calculations of the $c_{\Delta y}$ correction factor based on FONLL pQCD calculations [7] or on the assumption of uniform D-meson rapidity distribution in $|y|<y_{\rm fid}$ would give the same result, because both in PYTHIA and in FONLL the D-meson yield is uniform within 1% in the range $|y|<0.8$.

The $f_{\rm prompt}$ fraction was calculated using the B production cross sections from FONLL calculations [6, 41], the $\mathrm{B}\rightarrow\mathrm{D}+X$ decay kinematics from the EvtGen package [42] and the efficiencies for feed-down D mesons reported in Fig. 2:

[TABLE]

where the $p_{\rm T}$ dependence of $f_{\rm prompt}$, $N^{\rm D+\overline{D},raw}$ and $(\mathrm{Acc}\times\epsilon)_{\text{feed-down}}$ is omitted for brevity. The values of $f_{\rm prompt}$ range between 0.85 and 0.97 depending on D-meson species and $p_{\rm T}$.

3 Systematic uncertainties

Systematic uncertainties were estimated considering several sources. A summary is shown in Table 1 for two $p_{\rm T}$ intervals. New or refined procedures were used with respect to the analyses presented in [14, 16], in particular for the uncertainties on the signal yield extraction, the track reconstruction efficiency and the feed-down subtraction.

The systematic uncertainties on the yield extraction obtained from the fits to the invariant-mass distributions (mass difference for ${\rm D^{*+}}$ mesons) were evaluated by repeating the fits several times varying (i) the invariant-mass bin width, (ii) the lower and upper limits of the fit range, (iii) the background fit function (exponential function, first, second and third order polynomials were used for ${\rm D^{0}}$, ${\rm D^{+}}$ and ${\rm D_{s}^{+}}$ and a power law for the ${\rm D^{*+}}$), for a total of about few hundred fits for each D-meson species and $p_{\rm T}$ interval. In addition, the same approach was used with a bin counting method, in which the signal yield was obtained by integrating the invariant-mass distribution after subtracting the background estimated from a fit to the side-bands. The distributions of the signal yield obtained from these variations are consistent with a Gaussian shape and the mean of the distributions is close to the central value of the yield. The systematic uncertainty was defined as the R.M.S.  of this distribution.

The systematic uncertainty on the track reconstruction efficiency was estimated by varying the track-quality selection criteria and by comparing the probability to prolong tracks from the TPC inward to the ITS (‘matching efficiency’) in data and simulations. The variation of the track selection criteria, such as the minimum number of clusters in the TPC, was found to yield a 2% systematic effect on the cross section of ${\rm D^{0}}$ mesons (two-prong final state) and 3% for the other meson species (three-prong final states). The comparison of the matching efficiency in data and simulations was made after weighting the relative abundances of primary and secondary particles in the simulation to match those observed in data. This weighting is motivated by the observation that the matching efficiency is much larger for primary particles than for secondary particles produced far from the interaction point in decays of strange hadrons and in interactions of primary particles with the material of the detector. The fractions of primary and secondary particles were estimated, as a function of $p_{\rm T}$, by fitting the inclusive track impact parameter distributions in data and in the simulation with a sum of three template distributions for primary particles, for secondary particles from strange-hadron decays and for secondary particles produced in interactions of primary particles in the detector material. The templates were obtained from the simulation. After weighting the relative abundances in the simulation to match those in data, the systematic uncertainty on the matching efficiency was defined as the relative difference of the matching efficiencies in data and in the simulation. The study was made separately for particles identified as pions and as kaons using the TPC and TOF PID selections described in Section 2. The systematic uncertainty is 2% per track in the interval $2<p_{\rm T}<6$ GeV/$c$ and 1% at lower and higher $p_{\rm T}$. The per-track uncertainty was then propagated to the D mesons, taking into account the number and transverse momentum of their decay tracks, and added in quadrature to the component estimated from the track selection variation.

Systematic uncertainties can also arise from possible differences in the distributions and resolution of the geometric selection variables between data and the simulation. These uncertainties were evaluated by repeating the analysis with several sets of selection criteria and comparing the resulting corrected cross sections. More details can be found in [14].

To estimate the uncertainty on the PID selection efficiency, for the three non-strange D-meson species the analysis was repeated without PID selection. The resulting cross sections were found to be compatible with those obtained with the PID selection. Therefore, no systematic uncertainty was assigned. For the ${\rm D_{s}^{+}}$ meson, the lower signal yield and the larger combinatorial background prevented a signal estimation without particle identification, hence, in this case, a 3$\sigma$ PID selection, looser with respect to the PID strategy adopted in the analysis, was used to estimate a systematic uncertainty of about 7%.

The systematic effect on the efficiency due to a possible difference between the simulated and real $p_{\rm T}$ distribution of D mesons was estimated by using alternative D-meson $p_{\rm T}$ distributions from the PYTHIA 6 generator with Perugia-0 tune and from the FONLL pQCD calculation. More details can be found in [14].

The systematic uncertainty on the subtraction of feed-down from beauty-hadron decays includes the uncertainties of i) the B-meson production cross section from FONLL calculations, ii) the branching ratios of B mesons into D mesons [36] and iii) the relative abundances of B-meson species produced in the beauty-quark fragmentation [36]. The dominant contribution is the one originating from the FONLL calculations and it was estimated by varying the $p_{\rm T}$-differential cross section of feed-down D mesons within the theoretical uncertainties of the FONLL calculation. The procedure for the variation of the b-quark mass, of the perturbative scales and of the parton distribution functions is described in [7]. In previous analyses, an alternative method based on the ratio of the FONLL cross sections for feed-down and prompt D mesons was also used in the estimation of the systematic uncertainties. In this analysis it was no longer used, on the basis of the observation that FONLL calculations at LHC energies provide a good description of the production cross sections of $\rm B^{0}$, $\rm B^{+}$ and $\rm B_{s}^{0}$ mesons at both central and forward rapidity, while it underestimates prompt charm production  [43, 44, 45, 46, 47, 48]. Hence, the uncertainty due to the B feed-down correction is significantly reduced and more symmetric as compared to our previous publications.

The uncertainty on the D-meson production cross section normalisation has a contribution from the 3.5% uncertainty on the minimum-bias trigger cross section [37] and a contribution from the uncertainties on the branching ratios of the considered D-meson decay channels (see Table 1).

The total systematic uncertainties, which are obtained as a quadratic sum of the contributions listed in Table 1, are reduced by a factor that ranges from 1.5 to 5, depending on D-meson species and $p_{\rm T}$ interval, with respect to previous publications [14, 16]. The systematic uncertainties on PID, tracking and selection efficiencies are mostly correlated among the different $p_{\rm T}$ intervals, while the raw-yield extraction uncertainty is mostly uncorrelated.

4 Results

The $p_{\rm T}$-differential cross sections for prompt ${\rm D^{0}}$, ${\rm D^{+}}$, ${\rm D^{*+}}$ and ${\rm D_{s}^{+}}$ production in $|y|<0.5$ are shown in Fig. 3. The error bars represent the statistical uncertainties, while the systematic uncertainties are shown as boxes around the data points. The symbols are positioned horizontally at the centre of each $p_{\rm T}$ interval, with the horizontal bars representing the width of the $p_{\rm T}$ interval. For all D-meson species, the results are consistent within uncertainties with those reported in our previous publications on charmed-meson cross sections in pp collisions at $\sqrt{s}=7\leavevmode\nobreak\ \mathrm{TeV}$ [14, 16], but the total uncertainties (sum in quadrature of statistical and systematic errors) are reduced by a factor 1.5–4, depending on the D-meson species and the $p_{\rm T}$ interval. The ${\rm D^{0}}$-meson cross section in the interval $0<p_{\rm T}<1\leavevmode\nobreak\ \mathrm{GeV}/c$ is obtained from the analysis without decay vertex reconstruction described in Ref. [17]. At higher $p_{\rm T}$, the results of the analysis presented in this paper, based on geometrical selections on the displaced decay vertex, are more precise than those obtained without decay vertex reconstruction.

In Figs. 4–7, the measured $p_{\rm T}$-differential cross sections are compared with results from perturbative QCD calculations, two of which are based on collinear factorisation (FONLL [6, 7] and GM-VFNS [3, 4, 5]) and one is a leading order (LO) calculation based on $k_{\rm T}$-factorisation [9]. The results of these calculations, performed in the same $p_{\rm T}$ intervals of the measurement, are shown as filled boxes spanning the theoretical uncertainties and a solid line representing the values obtained with the central values of the pQCD parameters. The theoretical uncertainties are estimated in all the three frameworks by varying the renormalisation and factorisation scales. In the FONLL and $k_{\rm T}$-factorisation calculations also the effect of the charm-quark mass uncertainty is considered. In the FONLL and GM-VFNS calculations, the CTEQ6.6 PDFs [49] were used, and the uncertainty on the PDFs was included in the FONLL error boxes. The LO $k_{\rm T}$-factorisation calculations were performed with an updated set of unintegrated gluon-distribution functions computed from the recent MMHT2014-LO PDFs [50]. For this reason, the comparison to the measured ${\rm D^{0}}$-meson cross section differs from that reported in Ref. [17]. In the FONLL calculation, the fragmentation fractions $f(\rm c\to D)$, i.e. the fractions of charm quarks hadronising into each D-meson species, were taken from Ref. [51]. For the ${\rm D_{s}^{+}}$ mesons, only the comparisons to GM-VFNS and LO $k_{\rm T}$-factorisation predictions are shown, because a calculation of the ${\rm D_{s}^{+}}$ production cross section within the FONLL framework is not available. The central value of the GM-VFNS predictions lies systematically above the data, while that of the FONLL predictions lies below the data. For FONLL, this feature was observed also at other values of $\sqrt{s}$, from 0.2 to 13 TeV [11, 12, 15, 19, 20, 21]. The LO $k_{\rm T}$-factorisation calculation describes the data within uncertainties for $p_{\rm T}<2\leavevmode\nobreak\ \mathrm{GeV}/c$ and $p_{\rm T}>10\leavevmode\nobreak\ \mathrm{GeV}/c$, while in the interval $2<p_{\rm T}<10\leavevmode\nobreak\ \mathrm{GeV}/c$ the predictions underestimate the measured production cross sections.

The average transverse momentum ${\langle p_{{\mathrm{T}}}\rangle}$ of prompt ${\rm D^{0}}$ mesons was measured by fitting the cross section reported in Fig. 4 with a power-law function:

[TABLE]

where $C$, $p_{0}$ and $n$ are the free parameters. The prompt-${\rm D^{0}}$ ${\langle p_{{\mathrm{T}}}\rangle}$, defined as the mean value of the fit function, is:

[TABLE]

The systematic uncertainty on ${\langle p_{{\mathrm{T}}}\rangle}$ was estimated as described in Ref. [17] taking into account separately the contributions due to the correlated and uncorrelated systematic uncertainties on the measured $p_{\rm T}$-differential cross section. The uncertainty due to the fit function was estimated from the spread of the results obtained with different functions and using an alternative method, which is not based on fits to the distribution, but on direct calculations of ${\langle p_{{\mathrm{T}}}\rangle}$ from the data points.

The ratios of the $p_{\rm T}$-differential cross sections of ${\rm D^{0}}$, ${\rm D^{+}}$, ${\rm D^{*+}}$ and ${\rm D_{s}^{+}}$ mesons are reported in Fig. 8. In the evaluation of the systematic uncertainties on these ratios, the sources of correlated and uncorrelated systematic effects were treated separately. In particular, the contributions of the yield extraction and cut efficiency were considered as uncorrelated, while those of the feed-down from beauty-hadron decays and the tracking efficiency were treated as fully correlated among the different D-meson species. The measured D-meson ratios do not show a significant $p_{\rm T}$ dependence within the experimental uncertainties, thus suggesting a small difference between the fragmentation functions of charm quarks to pseudoscalar (${\rm D^{0}}$, ${\rm D^{+}}$ and ${\rm D_{s}^{+}}$) and vector (${\rm D^{*+}}$) mesons and to strange and non-strange mesons. The data are compared to the ratios of the D-meson cross sections from FONLL (only for ${\rm D^{0}}$, ${\rm D^{+}}$ and ${\rm D^{*+}}$ mesons), GM-VFNS and LO $k_{\rm T}$-factorisation pQCD calculations. The ratios of the theoretical predictions were computed assuming their uncertainties to be fully correlated among the D-meson species, which results in an almost complete cancellation of the uncertainties in the ratio. Note that in all these pQCD calculations, the relative abundances of the different D-meson species are not predicted by the theory, but the fragmentation fractions, $f({\rm c\rightarrow D})$, are taken from the experimental measurements [52, 7, 53, 9, 54, 51]. In the FONLL and GM-VFNS frameworks, the $p_{\rm T}$ dependence of the ratios of the D-meson production cross sections arises from the different fragmentation functions used to model the transfer of energy from the charm quark to a specific D-meson species [53, 52, 55], and from the different contribution from decays of higher excited states. The parton fragmentation models used in the calculations provide an adequate description of the measured data. In the LO $k_{\rm T}$-factorisation calculations, the same fragmentation function (Peterson [56]) is used for ${\rm D^{0}}$, ${\rm D^{+}}$ and ${\rm D_{s}^{+}}$ mesons, resulting in the same shape of the $p_{\rm T}$ distributions of these three meson species, while the fragmentation functions for vector mesons from Ref. [57] are used for ${\rm D^{*+}}$ mesons [9].

The ratios of ${\rm D^{0}}$-meson production cross sections in different rapidity intervals, which are expected to be sensitive to the gluon PDF at small values of Bjorken-$x$ [22], were computed from our measurement in the central rapidity region ($|y|<0.5$) and the results reported by the LHCb collaboration for pp collisions at $\sqrt{s}=7\leavevmode\nobreak\ \mathrm{TeV}$ in different $y$ intervals at forward rapidity [19]. The results are reported in Fig. 9, where the central-to-forward ratios are shown as a function of $p_{\rm T}$ for three different $y$ intervals at forward rapidity: $2<y<2.5$ (left panel), $3<y<3.5$ (middle panel), $4<y<4.5$ (right panel). The error bars represent the total uncertainty obtained from the propagation of the statistical and systematic uncertainties on the $p_{\rm T}$-differential cross sections. The measured ratios are compared to FONLL calculations, shown as boxes in Fig. 9. The central-to-forward ratios computed using the central values of the factorisation and renormalisation scales are found to describe the data within their uncertainties. The upper edge of the FONLL uncertainty band, which is also in agreement with the measured values of the central-to-forward ratios, is determined by the calculations with factorisation scale $\mu_{\rm F}=2\,m_{\rm T}$, where $m_{\rm T}=\sqrt{p_{\rm T}^{2}+m_{\rm c}^{2}}$ and $m_{\rm c}=1.5\leavevmode\nobreak\ \mathrm{GeV}/c^{2}$. The low edge of the FONLL uncertainty band is determined by the calculations with $\mu_{\rm F}=0.5\,m_{\rm T}$, which provide a worse description of the measured central-to-forward ratios at low $p_{\rm T}$ for the most forward rapidity interval. Note that in this forward rapidity interval, the FONLL calculation with $\mu_{\rm F}=0.5\,m_{\rm T}$ uses the PDFs for Bjorken-$x$ values reaching down to about $10^{-5}$, a region that is not constrained by experimental data, and below $Q^{2}=(1.3\leavevmode\nobreak\ \mathrm{GeV}/c)^{2}$, where the CTEQ6.6 PDFs [49] are kept constant to their values at $(1.3\leavevmode\nobreak\ \mathrm{GeV}/c)^{2}$.

The visible cross sections of prompt D mesons, obtained by integrating the $p_{\rm T}$-differential cross sections in the measured $p_{\rm T}$ range, are reported in Table 2. In addition, for ${\rm D^{0}}$ mesons the cross sections integrated over the $p_{\rm T}$ intervals of the ${\rm D^{+}}$, ${\rm D^{*+}}$ and ${\rm D_{s}^{+}}$ measurements are shown. The systematic uncertainty was defined by propagating the yield extraction uncertainties as uncorrelated among $p_{\rm T}$ intervals and all the other uncertainties as correlated. These values were used to compute the ratios of the $p_{\rm T}$-integrated D-meson production cross sections, which are reported in Table 3. The systematic uncertainties on the ratios were computed taking into account the sources correlated and uncorrelated among the different D-meson species as described above. The measured ratios are compatible within uncertainties with the results at $\sqrt{s}=2.76\leavevmode\nobreak\ \mathrm{TeV}$ [15] and with the measurements of the LHCb collaboration at forward rapidity ($2.0<y<4.5$) at three different collision energies $\sqrt{s}=$ 5, 7 and 13 TeV [19, 20, 21]. The measured $p_{\rm T}$-integrated production ratios are also compatible with the charm-quark fragmentation fractions $f(\rm c\to D)$ measured in ${\rm e^{+}e^{-}}$ collisions from the compilation in [51]. These results indicate that the fragmentation fractions of charm quarks into different D-meson species do not vary substantially with rapidity, collision energy and colliding system.

The production cross sections per unit of rapidity, ${\rm d}\sigma/{\rm d}y$, at mid-rapidity were computed for each meson species by extrapolating the visible cross section to the full $p_{\rm T}$ range. The extrapolation factor for a given D-meson species was defined as the ratio between the total production cross section in $|y|<0.5$ and that in the experimentally covered phase space, both of them calculated with the FONLL central parameters. The systematic uncertainty on the extrapolation factor was estimated by considering the contributions due to i) the uncertainties on the CTEQ6.6 PDFs [49] and ii) the variation of the charm-quark mass and the renormalisation and factorisation scales in the FONLL calculation, as proposed in [7]. For ${\rm D^{0}}$ mesons, which are measured down to $p_{\rm T}=0$, the extrapolation factor accounts only for the very small contribution of D-mesons with $p_{\rm T}>36\leavevmode\nobreak\ \mathrm{GeV}/c$ and it has therefore a value very close to unity with negligible uncertainty. In the case of ${\rm D_{s}^{+}}$ mesons, for which a FONLL prediction is not available, the central value of the extrapolation factor was computed from the prediction based on the $p_{\rm T}$-differential cross section of charm quarks from FONLL, the fractions $f({\rm c\rightarrow{\rm D_{s}^{+}}})$ and $f({\rm c\rightarrow D_{\rm s}^{*+}})$ from ALEPH [54], and the fragmentation functions from [57], which have one parameter, $r$, that was set to 0.1 as done in FONLL [53]. The ${\rm D}_{\rm s}^{*+}$ mesons produced in the c quark fragmentation were made to decay with PYTHIA and the resulting ${\rm D_{s}^{+}}$ mesons were summed to the primary ones to obtain the prompt yield. An additional contribution to the systematic uncertainty was assigned for ${\rm D_{s}^{+}}$ mesons based on the envelope of the results obtained using the FONLL $p_{\rm T}$-differential cross sections of ${\rm D^{0}}$, ${\rm D^{+}}$ and ${\rm D^{*+}}$ mesons to compute the ${\rm D_{s}^{+}}$ extrapolation factor. The resulting values for the extrapolation factors and for the prompt D-meson production cross sections per unit of rapidity ${\rm d}\sigma/{\rm d}y$ are reported in Table 4.

The ${\rm c\overline{c}}$ production cross section per unit of rapidity at mid-rapidity ($|y|<0.5$) was calculated by dividing the prompt ${\rm D^{0}}$-meson cross section by the fraction of charm quarks hadronising into ${\rm D^{0}}$ mesons $f(c\rightarrow{\rm D^{0}})$ and correcting for the different shapes of the distributions of $y_{{\rm D^{0}}}$ and $y_{\rm c\overline{c}}$ (${\rm c\overline{c}}$ pair rapidity). The correction factor and its uncertainty were extracted from FONLL and MNR NLO pQCD [58] calculations together with PYTHIA 6 [38] and POWHEG [59] simulations, as described in detail in Ref. [17]. For the fragmentation fraction, the value $f(c\rightarrow{\rm D^{0}})=0.542\pm 0.024$ derived in Ref. [51] by averaging the measurements from e+e- collisions at LEP was used. As pointed out in Refs. [60, 61], measurements in e+e-, ep and pp collisions agree within uncertainties, supporting the hypothesis that fragmentation is independent of the specific production process111In Ref. [61], an average of the charm fragmentation fractions over the measurements from all collision systems is calculated, imposing the constraint that the sum of all weakly-decaying charmed hadrons is unity, which results in $f(c\rightarrow{\rm D^{0}})=0.6086\pm 0.0076$ (about 11% larger that the value from [51]).. The resulting ${\rm c\overline{c}}$ cross section per unit of rapidity at mid-rapidity is:

[TABLE]

We verified that the precision of the ${\rm c\overline{c}}$ production cross-section determination does not improve if the results calculated from ${\rm D^{+}}$, ${\rm D^{*+}}$ and ${\rm D_{s}^{+}}$ mesons, which have significantly larger extrapolation uncertainties as compared to the ${\rm D^{0}}$ one, are included via a weighted average procedure, as done in Ref. [15]. The total production cross section of prompt ${\rm D^{0}}$ mesons (average of particles and antiparticles) was calculated by extrapolating to full phase space the cross section measured at mid-rapidity. The extrapolation factor was defined as the ratio of the ${\rm D^{0}}$ production cross sections in full rapidity and in $|y|<0.5$ calculated with the FONLL central parameters: $8.56^{+2.51}_{-0.42}$. The systematic uncertainty on the extrapolation factor was estimated with the same procedure described above for the $p_{\rm T}$ extrapolation. The resulting cross section is:

[TABLE]

The total charm production cross section was calculated by dividing the total prompt ${\rm D^{0}}$-meson production cross section by the fragmentation fraction reported above. The resulting ${\rm c\overline{c}}$ production cross section in pp collisions at $\sqrt{s}=7\leavevmode\nobreak\ \mathrm{TeV}$ is:

[TABLE]

which is consistent with the value of Ref. [17] but has smaller statistical and systematic uncertainties. It is also compatible within uncertainties with the total charm production cross section reported by the ATLAS collaboration [13], which is calculated from ${\rm D^{+}}$ and ${\rm D^{*+}}$ measurements in $|\eta|<2.1$ and $p_{\rm T}>3.5\leavevmode\nobreak\ \mathrm{GeV}/c$ and has larger uncertainties on the extrapolation to full kinematic phase space as compared to our result.

A more precise determination of the ${\rm c\overline{c}}$ production cross section can be obtained by summing our measurement of the prompt ${\rm D^{0}}$-meson cross section in $|y|<0.5$ and the LHCb result in $2<y<4.5$ for $0<p_{\rm T}<8\leavevmode\nobreak\ \mathrm{GeV}/c$ [19], and extrapolating to full rapidity and $p_{\rm T}$ via the ratio of FONLL calculations of the cross sections in full phase space and in the measured $y$ and $p_{\rm T}$ intervals exploiting the symmetry around $y=0$. The result for the ${\rm c\overline{c}}$ production cross section is:

[TABLE]

where the +0.11 mb extrapolation uncertainty is determined by FONLL calculations with factorisation scale $\mu_{\rm F}=0.5\,m_{\rm T}$, which do not describe the measured central-to-forward ratios of Fig. 9. If this $\mu_{\rm F}$ value is not considered, the extrapolation uncertainty is reduced to $\pm 0.05$ mb.

5 Summary

We have presented a new measurement of the inclusive $p_{\rm T}$-differential production cross sections of prompt ${\rm D^{0}}$, ${\rm D^{+}}$, ${\rm D^{*+}}$ and ${\rm D_{s}^{+}}$ mesons at mid-rapidity ($|y|<0.5$) in pp collisions at a centre-of-mass energy of $\sqrt{s}=7\leavevmode\nobreak\ \mathrm{TeV}$. The measurements cover the transverse-momentum interval $0<p_{\rm T}<36\leavevmode\nobreak\ \mathrm{GeV}/c$ for ${\rm D^{0}}$ mesons, $1<p_{\rm T}<24\leavevmode\nobreak\ \mathrm{GeV}/c$ for ${\rm D^{+}}$ and ${\rm D^{*+}}$ mesons, and $2<p_{\rm T}<12\leavevmode\nobreak\ \mathrm{GeV}/c$ for ${\rm D_{s}^{+}}$ mesons. As compared to previously published results based on the same data sample [14, 16], the present results have an extended $p_{\rm T}$ coverage and total uncertainties reduced by a factor of about 1.5–4 depending on the D-meson species and $p_{\rm T}$. The measurements cover complementary ranges in $p_{\rm T}$ and $y$ with respect to those of the ATLAS ($3.5<p_{\rm T}<100\leavevmode\nobreak\ \mathrm{GeV}/c$, $|\eta|<2.1$ [13]) and LHCb ($0<p_{\rm T}<8\leavevmode\nobreak\ \mathrm{GeV}/c$, $2<y<4.5$ [19]) Collaborations at the same centre-of-mass energy. The $p_{\rm T}$-differential cross sections are described within uncertainties in the full $p_{\rm T}$ range by the FONLL and GM-VFNS perturbative QCD calculations, which are based on collinear factorisation, while a leading-order calculation based on $k_{\rm T}$ factorisation underestimates the measured cross sections for $2<p_{\rm T}<10\leavevmode\nobreak\ \mathrm{GeV}/c$. The $p_{\rm T}$-differential ratios of our measurement at mid-rapidity and LHCb measurements at forward rapidity [19] are described by FONLL calculations. These central-to-forward ratios, once complemented with similar measurements at different centre-of-mass energies, could provide sensitivity to the gluon PDF at small values of Bjorken-$x$ [22]. The ratios of the cross sections of the four D-meson species were found to be compatible with the LHCb measurements at forward rapidity and different collision energies as well as with results from ${\rm e^{+}e^{-}}$ collisions, indicating that the fragmentation fractions of charm quarks into different D-meson species do not vary substantially with rapidity, collision energy and colliding system.

The new measurement also allowed for a more accurate determination of the $p_{\rm T}$-integrated ${\rm c\overline{c}}$ production cross section at mid-rapidity in pp collisions at $\sqrt{s}=7\leavevmode\nobreak\ \mathrm{TeV}$:

[TABLE]

In particular, the total systematic uncertainty of this measurement is about $\pm 10\%$, while it was ${}^{+13}_{-21}\%$ for the previously-published measurement [17].

The total ${\rm c\overline{c}}$ production cross section in full phase space was calculated by combining the above measurement at mid-rapidity with that at forward rapidity by the LHCb Collaboration:

[TABLE]

Acknowledgements

The ALICE Collaboration would like to thank all its engineers and technicians for their invaluable contributions to the construction of the experiment and the CERN accelerator teams for the outstanding performance of the LHC complex. The ALICE Collaboration gratefully acknowledges the resources and support provided by all Grid centres and the Worldwide LHC Computing Grid (WLCG) collaboration. The ALICE Collaboration acknowledges the following funding agencies for their support in building and running the ALICE detector: A. I. Alikhanyan National Science Laboratory (Yerevan Physics Institute) Foundation (ANSL), State Committee of Science and World Federation of Scientists (WFS), Armenia; Austrian Academy of Sciences and Nationalstiftung für Forschung, Technologie und Entwicklung, Austria; Ministry of Communications and High Technologies, National Nuclear Research Center, Azerbaijan; Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Universidade Federal do Rio Grande do Sul (UFRGS), Financiadora de Estudos e Projetos (Finep) and Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP), Brazil; Ministry of Science & Technology of China (MSTC), National Natural Science Foundation of China (NSFC) and Ministry of Education of China (MOEC) , China; Ministry of Science, Education and Sport and Croatian Science Foundation, Croatia; Ministry of Education, Youth and Sports of the Czech Republic, Czech Republic; The Danish Council for Independent Research — Natural Sciences, the Carlsberg Foundation and Danish National Research Foundation (DNRF), Denmark; Helsinki Institute of Physics (HIP), Finland; Commissariat à l’Energie Atomique (CEA) and Institut National de Physique Nucléaire et de Physique des Particules (IN2P3) and Centre National de la Recherche Scientifique (CNRS), France; Bundesministerium für Bildung, Wissenschaft, Forschung und Technologie (BMBF) and GSI Helmholtzzentrum für Schwerionenforschung GmbH, Germany; Ministry of Education, Research and Religious Affairs, Greece; National Research, Development and Innovation Office, Hungary; Department of Atomic Energy Government of India (DAE) and Council of Scientific and Industrial Research (CSIR), New Delhi, India; Indonesian Institute of Science, Indonesia; Centro Fermi - Museo Storico della Fisica e Centro Studi e Ricerche Enrico Fermi and Istituto Nazionale di Fisica Nucleare (INFN), Italy; Institute for Innovative Science and Technology , Nagasaki Institute of Applied Science (IIST), Japan Society for the Promotion of Science (JSPS) KAKENHI and Japanese Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan; Consejo Nacional de Ciencia (CONACYT) y Tecnología, through Fondo de Cooperación Internacional en Ciencia y Tecnología (FONCICYT) and Dirección General de Asuntos del Personal Academico (DGAPA), Mexico; Nationaal instituut voor subatomaire fysica (Nikhef), Netherlands; The Research Council of Norway, Norway; Commission on Science and Technology for Sustainable Development in the South (COMSATS), Pakistan; Pontificia Universidad Católica del Perú, Peru; Ministry of Science and Higher Education and National Science Centre, Poland; Korea Institute of Science and Technology Information and National Research Foundation of Korea (NRF), Republic of Korea; Ministry of Education and Scientific Research, Institute of Atomic Physics and Romanian National Agency for Science, Technology and Innovation, Romania; Joint Institute for Nuclear Research (JINR), Ministry of Education and Science of the Russian Federation and National Research Centre Kurchatov Institute, Russia; Ministry of Education, Science, Research and Sport of the Slovak Republic, Slovakia; National Research Foundation of South Africa, South Africa; Centro de Aplicaciones Tecnológicas y Desarrollo Nuclear (CEADEN), Cubaenergía, Cuba, Ministerio de Ciencia e Innovacion and Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (CIEMAT), Spain; Swedish Research Council (VR) and Knut & Alice Wallenberg Foundation (KAW), Sweden; European Organization for Nuclear Research, Switzerland; National Science and Technology Development Agency (NSDTA), Suranaree University of Technology (SUT) and Office of the Higher Education Commission under NRU project of Thailand, Thailand; Turkish Atomic Energy Agency (TAEK), Turkey; National Academy of Sciences of Ukraine, Ukraine; Science and Technology Facilities Council (STFC), United Kingdom; National Science Foundation of the United States of America (NSF) and United States Department of Energy, Office of Nuclear Physics (DOE NP), United States of America.

Appendix A The ALICE Collaboration

S. Acharya${}^{\textrm{\scriptsize 139}}$, D. Adamová${}^{\textrm{\scriptsize 87}}$, M.M. Aggarwal${}^{\textrm{\scriptsize 91}}$, G. Aglieri Rinella${}^{\textrm{\scriptsize 34}}$, M. Agnello${}^{\textrm{\scriptsize 30}}$, N. Agrawal${}^{\textrm{\scriptsize 47}}$, Z. Ahammed${}^{\textrm{\scriptsize 139}}$, N. Ahmad${}^{\textrm{\scriptsize 17}}$, S.U. Ahn${}^{\textrm{\scriptsize 69}}$, S. Aiola${}^{\textrm{\scriptsize 143}}$, A. Akindinov${}^{\textrm{\scriptsize 54}}$, S.N. Alam${}^{\textrm{\scriptsize 139}}$, D.S.D. Albuquerque${}^{\textrm{\scriptsize 124}}$, D. Aleksandrov${}^{\textrm{\scriptsize 83}}$, B. Alessandro${}^{\textrm{\scriptsize 113}}$, D. Alexandre${}^{\textrm{\scriptsize 104}}$, R. Alfaro Molina${}^{\textrm{\scriptsize 64}}$, A. Alici${}^{\textrm{\scriptsize 26}}$,${}^{\textrm{\scriptsize 12}}$,${}^{\textrm{\scriptsize 107}}$, A. Alkin${}^{\textrm{\scriptsize 3}}$, J. Alme${}^{\textrm{\scriptsize 21}}$, T. Alt${}^{\textrm{\scriptsize 41}}$, I. Altsybeev${}^{\textrm{\scriptsize 138}}$, C. Alves Garcia Prado${}^{\textrm{\scriptsize 123}}$, M. An${}^{\textrm{\scriptsize 7}}$, C. Andrei${}^{\textrm{\scriptsize 80}}$, H.A. Andrews${}^{\textrm{\scriptsize 104}}$, A. Andronic${}^{\textrm{\scriptsize 100}}$, V. Anguelov${}^{\textrm{\scriptsize 96}}$, C. Anson${}^{\textrm{\scriptsize 90}}$, T. Antičić${}^{\textrm{\scriptsize 101}}$, F. Antinori${}^{\textrm{\scriptsize 110}}$, P. Antonioli${}^{\textrm{\scriptsize 107}}$, R. Anwar${}^{\textrm{\scriptsize 126}}$, L. Aphecetche${}^{\textrm{\scriptsize 116}}$, H. Appelshäuser${}^{\textrm{\scriptsize 60}}$, S. Arcelli${}^{\textrm{\scriptsize 26}}$, R. Arnaldi${}^{\textrm{\scriptsize 113}}$, O.W. Arnold${}^{\textrm{\scriptsize 97}}$,${}^{\textrm{\scriptsize 35}}$, I.C. Arsene${}^{\textrm{\scriptsize 20}}$, M. Arslandok${}^{\textrm{\scriptsize 60}}$, B. Audurier${}^{\textrm{\scriptsize 116}}$, A. Augustinus${}^{\textrm{\scriptsize 34}}$, R. Averbeck${}^{\textrm{\scriptsize 100}}$, M.D. Azmi${}^{\textrm{\scriptsize 17}}$, A. Badalà${}^{\textrm{\scriptsize 109}}$, Y.W. Baek${}^{\textrm{\scriptsize 68}}$, S. Bagnasco${}^{\textrm{\scriptsize 113}}$, R. Bailhache${}^{\textrm{\scriptsize 60}}$, R. Bala${}^{\textrm{\scriptsize 93}}$, A. Baldisseri${}^{\textrm{\scriptsize 65}}$, M. Ball${}^{\textrm{\scriptsize 44}}$, R.C. Baral${}^{\textrm{\scriptsize 57}}$, A.M. Barbano${}^{\textrm{\scriptsize 25}}$, R. Barbera${}^{\textrm{\scriptsize 27}}$, F. Barile${}^{\textrm{\scriptsize 32}}$,${}^{\textrm{\scriptsize 106}}$, L. Barioglio${}^{\textrm{\scriptsize 25}}$, G.G. Barnaföldi${}^{\textrm{\scriptsize 142}}$, L.S. Barnby${}^{\textrm{\scriptsize 34}}$,${}^{\textrm{\scriptsize 104}}$, V. Barret${}^{\textrm{\scriptsize 71}}$, P. Bartalini${}^{\textrm{\scriptsize 7}}$, K. Barth${}^{\textrm{\scriptsize 34}}$, J. Bartke${}^{\textrm{\scriptsize 120}}$\Aref0, E. Bartsch${}^{\textrm{\scriptsize 60}}$, M. Basile${}^{\textrm{\scriptsize 26}}$, N. Bastid${}^{\textrm{\scriptsize 71}}$, S. Basu${}^{\textrm{\scriptsize 139}}$, B. Bathen${}^{\textrm{\scriptsize 61}}$, G. Batigne${}^{\textrm{\scriptsize 116}}$, A. Batista Camejo${}^{\textrm{\scriptsize 71}}$, B. Batyunya${}^{\textrm{\scriptsize 67}}$, P.C. Batzing${}^{\textrm{\scriptsize 20}}$, I.G. Bearden${}^{\textrm{\scriptsize 84}}$, H. Beck${}^{\textrm{\scriptsize 96}}$, C. Bedda${}^{\textrm{\scriptsize 30}}$, N.K. Behera${}^{\textrm{\scriptsize 50}}$, I. Belikov${}^{\textrm{\scriptsize 135}}$, F. Bellini${}^{\textrm{\scriptsize 26}}$, H. Bello Martinez${}^{\textrm{\scriptsize 2}}$, R. Bellwied${}^{\textrm{\scriptsize 126}}$, L.G.E. Beltran${}^{\textrm{\scriptsize 122}}$, V. Belyaev${}^{\textrm{\scriptsize 76}}$, G. Bencedi${}^{\textrm{\scriptsize 142}}$, S. Beole${}^{\textrm{\scriptsize 25}}$, A. Bercuci${}^{\textrm{\scriptsize 80}}$, Y. Berdnikov${}^{\textrm{\scriptsize 89}}$, D. Berenyi${}^{\textrm{\scriptsize 142}}$, R.A. Bertens${}^{\textrm{\scriptsize 53}}$,${}^{\textrm{\scriptsize 129}}$, D. Berzano${}^{\textrm{\scriptsize 34}}$, L. Betev${}^{\textrm{\scriptsize 34}}$, A. Bhasin${}^{\textrm{\scriptsize 93}}$, I.R. Bhat${}^{\textrm{\scriptsize 93}}$, A.K. Bhati${}^{\textrm{\scriptsize 91}}$, B. Bhattacharjee${}^{\textrm{\scriptsize 43}}$, J. Bhom${}^{\textrm{\scriptsize 120}}$, L. Bianchi${}^{\textrm{\scriptsize 126}}$, N. Bianchi${}^{\textrm{\scriptsize 73}}$, C. Bianchin${}^{\textrm{\scriptsize 141}}$, J. Bielčík${}^{\textrm{\scriptsize 38}}$, J. Bielčíková${}^{\textrm{\scriptsize 87}}$, A. Bilandzic${}^{\textrm{\scriptsize 35}}$,${}^{\textrm{\scriptsize 97}}$, G. Biro${}^{\textrm{\scriptsize 142}}$, R. Biswas${}^{\textrm{\scriptsize 4}}$, S. Biswas${}^{\textrm{\scriptsize 4}}$, J.T. Blair${}^{\textrm{\scriptsize 121}}$, D. Blau${}^{\textrm{\scriptsize 83}}$, C. Blume${}^{\textrm{\scriptsize 60}}$, G. Boca${}^{\textrm{\scriptsize 136}}$, F. Bock${}^{\textrm{\scriptsize 75}}$,${}^{\textrm{\scriptsize 96}}$, A. Bogdanov${}^{\textrm{\scriptsize 76}}$, L. Boldizsár${}^{\textrm{\scriptsize 142}}$, M. Bombara${}^{\textrm{\scriptsize 39}}$, G. Bonomi${}^{\textrm{\scriptsize 137}}$, M. Bonora${}^{\textrm{\scriptsize 34}}$, J. Book${}^{\textrm{\scriptsize 60}}$, H. Borel${}^{\textrm{\scriptsize 65}}$, A. Borissov${}^{\textrm{\scriptsize 99}}$, M. Borri${}^{\textrm{\scriptsize 128}}$, E. Botta${}^{\textrm{\scriptsize 25}}$, C. Bourjau${}^{\textrm{\scriptsize 84}}$, P. Braun-Munzinger${}^{\textrm{\scriptsize 100}}$, M. Bregant${}^{\textrm{\scriptsize 123}}$, T.A. Broker${}^{\textrm{\scriptsize 60}}$, T.A. Browning${}^{\textrm{\scriptsize 98}}$, M. Broz${}^{\textrm{\scriptsize 38}}$, E.J. Brucken${}^{\textrm{\scriptsize 45}}$, E. Bruna${}^{\textrm{\scriptsize 113}}$, G.E. Bruno${}^{\textrm{\scriptsize 32}}$, D. Budnikov${}^{\textrm{\scriptsize 102}}$, H. Buesching${}^{\textrm{\scriptsize 60}}$, S. Bufalino${}^{\textrm{\scriptsize 30}}$, P. Buhler${}^{\textrm{\scriptsize 115}}$, S.A.I. Buitron${}^{\textrm{\scriptsize 62}}$, P. Buncic${}^{\textrm{\scriptsize 34}}$, O. Busch${}^{\textrm{\scriptsize 132}}$, Z. Buthelezi${}^{\textrm{\scriptsize 66}}$, J.B. Butt${}^{\textrm{\scriptsize 15}}$, J.T. Buxton${}^{\textrm{\scriptsize 18}}$, J. Cabala${}^{\textrm{\scriptsize 118}}$, D. Caffarri${}^{\textrm{\scriptsize 34}}$, H. Caines${}^{\textrm{\scriptsize 143}}$, A. Caliva${}^{\textrm{\scriptsize 53}}$, E. Calvo Villar${}^{\textrm{\scriptsize 105}}$, P. Camerini${}^{\textrm{\scriptsize 24}}$, A.A. Capon${}^{\textrm{\scriptsize 115}}$, F. Carena${}^{\textrm{\scriptsize 34}}$, W. Carena${}^{\textrm{\scriptsize 34}}$, F. Carnesecchi${}^{\textrm{\scriptsize 26}}$,${}^{\textrm{\scriptsize 12}}$, J. Castillo Castellanos${}^{\textrm{\scriptsize 65}}$, A.J. Castro${}^{\textrm{\scriptsize 129}}$, E.A.R. Casula${}^{\textrm{\scriptsize 23}}$,${}^{\textrm{\scriptsize 108}}$, C. Ceballos Sanchez${}^{\textrm{\scriptsize 9}}$, P. Cerello${}^{\textrm{\scriptsize 113}}$, B. Chang${}^{\textrm{\scriptsize 127}}$, S. Chapeland${}^{\textrm{\scriptsize 34}}$, M. Chartier${}^{\textrm{\scriptsize 128}}$, J.L. Charvet${}^{\textrm{\scriptsize 65}}$, S. Chattopadhyay${}^{\textrm{\scriptsize 139}}$, S. Chattopadhyay${}^{\textrm{\scriptsize 103}}$, A. Chauvin${}^{\textrm{\scriptsize 97}}$,${}^{\textrm{\scriptsize 35}}$, M. Cherney${}^{\textrm{\scriptsize 90}}$, C. Cheshkov${}^{\textrm{\scriptsize 134}}$, B. Cheynis${}^{\textrm{\scriptsize 134}}$, V. Chibante Barroso${}^{\textrm{\scriptsize 34}}$, D.D. Chinellato${}^{\textrm{\scriptsize 124}}$, S. Cho${}^{\textrm{\scriptsize 50}}$, P. Chochula${}^{\textrm{\scriptsize 34}}$, K. Choi${}^{\textrm{\scriptsize 99}}$, M. Chojnacki${}^{\textrm{\scriptsize 84}}$, S. Choudhury${}^{\textrm{\scriptsize 139}}$, P. Christakoglou${}^{\textrm{\scriptsize 85}}$, C.H. Christensen${}^{\textrm{\scriptsize 84}}$, P. Christiansen${}^{\textrm{\scriptsize 33}}$, T. Chujo${}^{\textrm{\scriptsize 132}}$, S.U. Chung${}^{\textrm{\scriptsize 99}}$, C. Cicalo${}^{\textrm{\scriptsize 108}}$, L. Cifarelli${}^{\textrm{\scriptsize 12}}$,${}^{\textrm{\scriptsize 26}}$, F. Cindolo${}^{\textrm{\scriptsize 107}}$, J. Cleymans${}^{\textrm{\scriptsize 92}}$, F. Colamaria${}^{\textrm{\scriptsize 32}}$, D. Colella${}^{\textrm{\scriptsize 55}}$,${}^{\textrm{\scriptsize 34}}$, A. Collu${}^{\textrm{\scriptsize 75}}$, M. Colocci${}^{\textrm{\scriptsize 26}}$, M. Concas${}^{\textrm{\scriptsize 113}}$\Arefidp1791728, G. Conesa Balbastre${}^{\textrm{\scriptsize 72}}$, Z. Conesa del Valle${}^{\textrm{\scriptsize 51}}$, M.E. Connors${}^{\textrm{\scriptsize 143}}$\Arefidp1811120, J.G. Contreras${}^{\textrm{\scriptsize 38}}$, T.M. Cormier${}^{\textrm{\scriptsize 88}}$, Y. Corrales Morales${}^{\textrm{\scriptsize 113}}$, I. Cortés Maldonado${}^{\textrm{\scriptsize 2}}$, P. Cortese${}^{\textrm{\scriptsize 31}}$, M.R. Cosentino${}^{\textrm{\scriptsize 125}}$, F. Costa${}^{\textrm{\scriptsize 34}}$, S. Costanza${}^{\textrm{\scriptsize 136}}$, J. Crkovská${}^{\textrm{\scriptsize 51}}$, P. Crochet${}^{\textrm{\scriptsize 71}}$, E. Cuautle${}^{\textrm{\scriptsize 62}}$, L. Cunqueiro${}^{\textrm{\scriptsize 61}}$, T. Dahms${}^{\textrm{\scriptsize 35}}$,${}^{\textrm{\scriptsize 97}}$, A. Dainese${}^{\textrm{\scriptsize 110}}$, M.C. Danisch${}^{\textrm{\scriptsize 96}}$, A. Danu${}^{\textrm{\scriptsize 58}}$, D. Das${}^{\textrm{\scriptsize 103}}$, I. Das${}^{\textrm{\scriptsize 103}}$, S. Das${}^{\textrm{\scriptsize 4}}$, A. Dash${}^{\textrm{\scriptsize 81}}$, S. Dash${}^{\textrm{\scriptsize 47}}$, S. De${}^{\textrm{\scriptsize 48}}$,${}^{\textrm{\scriptsize 123}}$, A. De Caro${}^{\textrm{\scriptsize 29}}$, G. de Cataldo${}^{\textrm{\scriptsize 106}}$, C. de Conti${}^{\textrm{\scriptsize 123}}$, J. de Cuveland${}^{\textrm{\scriptsize 41}}$, A. De Falco${}^{\textrm{\scriptsize 23}}$, D. De Gruttola${}^{\textrm{\scriptsize 12}}$,${}^{\textrm{\scriptsize 29}}$, N. De Marco${}^{\textrm{\scriptsize 113}}$, S. De Pasquale${}^{\textrm{\scriptsize 29}}$, R.D. De Souza${}^{\textrm{\scriptsize 124}}$, H.F. Degenhardt${}^{\textrm{\scriptsize 123}}$, A. Deisting${}^{\textrm{\scriptsize 100}}$,${}^{\textrm{\scriptsize 96}}$, A. Deloff${}^{\textrm{\scriptsize 79}}$, C. Deplano${}^{\textrm{\scriptsize 85}}$, P. Dhankher${}^{\textrm{\scriptsize 47}}$, D. Di Bari${}^{\textrm{\scriptsize 32}}$, A. Di Mauro${}^{\textrm{\scriptsize 34}}$, P. Di Nezza${}^{\textrm{\scriptsize 73}}$, B. Di Ruzza${}^{\textrm{\scriptsize 110}}$, M.A. Diaz Corchero${}^{\textrm{\scriptsize 10}}$, T. Dietel${}^{\textrm{\scriptsize 92}}$, P. Dillenseger${}^{\textrm{\scriptsize 60}}$, R. Divià${}^{\textrm{\scriptsize 34}}$, Ø. Djuvsland${}^{\textrm{\scriptsize 21}}$, A. Dobrin${}^{\textrm{\scriptsize 58}}$,${}^{\textrm{\scriptsize 34}}$, D. Domenicis Gimenez${}^{\textrm{\scriptsize 123}}$, B. Dönigus${}^{\textrm{\scriptsize 60}}$, O. Dordic${}^{\textrm{\scriptsize 20}}$, T. Drozhzhova${}^{\textrm{\scriptsize 60}}$, A.K. Dubey${}^{\textrm{\scriptsize 139}}$, A. Dubla${}^{\textrm{\scriptsize 100}}$, L. Ducroux${}^{\textrm{\scriptsize 134}}$, A.K. Duggal${}^{\textrm{\scriptsize 91}}$, P. Dupieux${}^{\textrm{\scriptsize 71}}$, R.J. Ehlers${}^{\textrm{\scriptsize 143}}$, D. Elia${}^{\textrm{\scriptsize 106}}$, E. Endress${}^{\textrm{\scriptsize 105}}$, H. Engel${}^{\textrm{\scriptsize 59}}$, E. Epple${}^{\textrm{\scriptsize 143}}$, B. Erazmus${}^{\textrm{\scriptsize 116}}$, F. Erhardt${}^{\textrm{\scriptsize 133}}$, B. Espagnon${}^{\textrm{\scriptsize 51}}$, S. Esumi${}^{\textrm{\scriptsize 132}}$, G. Eulisse${}^{\textrm{\scriptsize 34}}$, J. Eum${}^{\textrm{\scriptsize 99}}$, D. Evans${}^{\textrm{\scriptsize 104}}$, S. Evdokimov${}^{\textrm{\scriptsize 114}}$, L. Fabbietti${}^{\textrm{\scriptsize 35}}$,${}^{\textrm{\scriptsize 97}}$, J. Faivre${}^{\textrm{\scriptsize 72}}$, A. Fantoni${}^{\textrm{\scriptsize 73}}$, M. Fasel${}^{\textrm{\scriptsize 88}}$,${}^{\textrm{\scriptsize 75}}$, L. Feldkamp${}^{\textrm{\scriptsize 61}}$, A. Feliciello${}^{\textrm{\scriptsize 113}}$, G. Feofilov${}^{\textrm{\scriptsize 138}}$, J. Ferencei${}^{\textrm{\scriptsize 87}}$, A. Fernández Téllez${}^{\textrm{\scriptsize 2}}$, E.G. Ferreiro${}^{\textrm{\scriptsize 16}}$, A. Ferretti${}^{\textrm{\scriptsize 25}}$, A. Festanti${}^{\textrm{\scriptsize 28}}$, V.J.G. Feuillard${}^{\textrm{\scriptsize 71}}$,${}^{\textrm{\scriptsize 65}}$, J. Figiel${}^{\textrm{\scriptsize 120}}$, M.A.S. Figueredo${}^{\textrm{\scriptsize 123}}$, S. Filchagin${}^{\textrm{\scriptsize 102}}$, D. Finogeev${}^{\textrm{\scriptsize 52}}$, F.M. Fionda${}^{\textrm{\scriptsize 23}}$, E.M. Fiore${}^{\textrm{\scriptsize 32}}$, M. Floris${}^{\textrm{\scriptsize 34}}$, S. Foertsch${}^{\textrm{\scriptsize 66}}$, P. Foka${}^{\textrm{\scriptsize 100}}$, S. Fokin${}^{\textrm{\scriptsize 83}}$, E. Fragiacomo${}^{\textrm{\scriptsize 112}}$, A. Francescon${}^{\textrm{\scriptsize 34}}$, A. Francisco${}^{\textrm{\scriptsize 116}}$, U. Frankenfeld${}^{\textrm{\scriptsize 100}}$, G.G. Fronze${}^{\textrm{\scriptsize 25}}$, U. Fuchs${}^{\textrm{\scriptsize 34}}$, C. Furget${}^{\textrm{\scriptsize 72}}$, A. Furs${}^{\textrm{\scriptsize 52}}$, M. Fusco Girard${}^{\textrm{\scriptsize 29}}$, J.J. Gaardhøje${}^{\textrm{\scriptsize 84}}$, M. Gagliardi${}^{\textrm{\scriptsize 25}}$, A.M. Gago${}^{\textrm{\scriptsize 105}}$, K. Gajdosova${}^{\textrm{\scriptsize 84}}$, M. Gallio${}^{\textrm{\scriptsize 25}}$, C.D. Galvan${}^{\textrm{\scriptsize 122}}$, P. Ganoti${}^{\textrm{\scriptsize 78}}$, C. Gao${}^{\textrm{\scriptsize 7}}$, C. Garabatos${}^{\textrm{\scriptsize 100}}$, E. Garcia-Solis${}^{\textrm{\scriptsize 13}}$, K. Garg${}^{\textrm{\scriptsize 27}}$, P. Garg${}^{\textrm{\scriptsize 48}}$, C. Gargiulo${}^{\textrm{\scriptsize 34}}$, P. Gasik${}^{\textrm{\scriptsize 97}}$,${}^{\textrm{\scriptsize 35}}$, E.F. Gauger${}^{\textrm{\scriptsize 121}}$, M.B. Gay Ducati${}^{\textrm{\scriptsize 63}}$, M. Germain${}^{\textrm{\scriptsize 116}}$, P. Ghosh${}^{\textrm{\scriptsize 139}}$, S.K. Ghosh${}^{\textrm{\scriptsize 4}}$, P. Gianotti${}^{\textrm{\scriptsize 73}}$, P. Giubellino${}^{\textrm{\scriptsize 113}}$,${}^{\textrm{\scriptsize 34}}$, P. Giubilato${}^{\textrm{\scriptsize 28}}$, E. Gladysz-Dziadus${}^{\textrm{\scriptsize 120}}$, P. Glässel${}^{\textrm{\scriptsize 96}}$, D.M. Goméz Coral${}^{\textrm{\scriptsize 64}}$, A. Gomez Ramirez${}^{\textrm{\scriptsize 59}}$, A.S. Gonzalez${}^{\textrm{\scriptsize 34}}$, V. Gonzalez${}^{\textrm{\scriptsize 10}}$, P. González-Zamora${}^{\textrm{\scriptsize 10}}$, S. Gorbunov${}^{\textrm{\scriptsize 41}}$, L. Görlich${}^{\textrm{\scriptsize 120}}$, S. Gotovac${}^{\textrm{\scriptsize 119}}$, V. Grabski${}^{\textrm{\scriptsize 64}}$, L.K. Graczykowski${}^{\textrm{\scriptsize 140}}$, K.L. Graham${}^{\textrm{\scriptsize 104}}$, L. Greiner${}^{\textrm{\scriptsize 75}}$, A. Grelli${}^{\textrm{\scriptsize 53}}$, C. Grigoras${}^{\textrm{\scriptsize 34}}$, V. Grigoriev${}^{\textrm{\scriptsize 76}}$, A. Grigoryan${}^{\textrm{\scriptsize 1}}$, S. Grigoryan${}^{\textrm{\scriptsize 67}}$, N. Grion${}^{\textrm{\scriptsize 112}}$, J.M. Gronefeld${}^{\textrm{\scriptsize 100}}$, F. Grosa${}^{\textrm{\scriptsize 30}}$, J.F. Grosse-Oetringhaus${}^{\textrm{\scriptsize 34}}$, R. Grosso${}^{\textrm{\scriptsize 100}}$, L. Gruber${}^{\textrm{\scriptsize 115}}$, F.R. Grull${}^{\textrm{\scriptsize 59}}$, F. Guber${}^{\textrm{\scriptsize 52}}$, R. Guernane${}^{\textrm{\scriptsize 72}}$, B. Guerzoni${}^{\textrm{\scriptsize 26}}$, K. Gulbrandsen${}^{\textrm{\scriptsize 84}}$, T. Gunji${}^{\textrm{\scriptsize 131}}$, A. Gupta${}^{\textrm{\scriptsize 93}}$, R. Gupta${}^{\textrm{\scriptsize 93}}$, I.B. Guzman${}^{\textrm{\scriptsize 2}}$, R. Haake${}^{\textrm{\scriptsize 34}}$, C. Hadjidakis${}^{\textrm{\scriptsize 51}}$, H. Hamagaki${}^{\textrm{\scriptsize 77}}$,${}^{\textrm{\scriptsize 131}}$, G. Hamar${}^{\textrm{\scriptsize 142}}$, J.C. Hamon${}^{\textrm{\scriptsize 135}}$, J.W. Harris${}^{\textrm{\scriptsize 143}}$, A. Harton${}^{\textrm{\scriptsize 13}}$, D. Hatzifotiadou${}^{\textrm{\scriptsize 107}}$, S. Hayashi${}^{\textrm{\scriptsize 131}}$, S.T. Heckel${}^{\textrm{\scriptsize 60}}$, E. Hellbär${}^{\textrm{\scriptsize 60}}$, H. Helstrup${}^{\textrm{\scriptsize 36}}$, A. Herghelegiu${}^{\textrm{\scriptsize 80}}$, G. Herrera Corral${}^{\textrm{\scriptsize 11}}$, F. Herrmann${}^{\textrm{\scriptsize 61}}$, B.A. Hess${}^{\textrm{\scriptsize 95}}$, K.F. Hetland${}^{\textrm{\scriptsize 36}}$, H. Hillemanns${}^{\textrm{\scriptsize 34}}$, B. Hippolyte${}^{\textrm{\scriptsize 135}}$, J. Hladky${}^{\textrm{\scriptsize 56}}$, B. Hohlweger${}^{\textrm{\scriptsize 97}}$, D. Horak${}^{\textrm{\scriptsize 38}}$, R. Hosokawa${}^{\textrm{\scriptsize 132}}$, P. Hristov${}^{\textrm{\scriptsize 34}}$, C. Hughes${}^{\textrm{\scriptsize 129}}$, T.J. Humanic${}^{\textrm{\scriptsize 18}}$, N. Hussain${}^{\textrm{\scriptsize 43}}$, T. Hussain${}^{\textrm{\scriptsize 17}}$, D. Hutter${}^{\textrm{\scriptsize 41}}$, D.S. Hwang${}^{\textrm{\scriptsize 19}}$, R. Ilkaev${}^{\textrm{\scriptsize 102}}$, M. Inaba${}^{\textrm{\scriptsize 132}}$, M. Ippolitov${}^{\textrm{\scriptsize 83}}$,${}^{\textrm{\scriptsize 76}}$, M. Irfan${}^{\textrm{\scriptsize 17}}$, V. Isakov${}^{\textrm{\scriptsize 52}}$, M.S. Islam${}^{\textrm{\scriptsize 48}}$, M. Ivanov${}^{\textrm{\scriptsize 34}}$,${}^{\textrm{\scriptsize 100}}$, V. Ivanov${}^{\textrm{\scriptsize 89}}$, V. Izucheev${}^{\textrm{\scriptsize 114}}$, B. Jacak${}^{\textrm{\scriptsize 75}}$, N. Jacazio${}^{\textrm{\scriptsize 26}}$, P.M. Jacobs${}^{\textrm{\scriptsize 75}}$, M.B. Jadhav${}^{\textrm{\scriptsize 47}}$, S. Jadlovska${}^{\textrm{\scriptsize 118}}$, J. Jadlovsky${}^{\textrm{\scriptsize 118}}$, S. Jaelani${}^{\textrm{\scriptsize 53}}$, C. Jahnke${}^{\textrm{\scriptsize 35}}$, M.J. Jakubowska${}^{\textrm{\scriptsize 140}}$, M.A. Janik${}^{\textrm{\scriptsize 140}}$, P.H.S.Y. Jayarathna${}^{\textrm{\scriptsize 126}}$, C. Jena${}^{\textrm{\scriptsize 81}}$, S. Jena${}^{\textrm{\scriptsize 126}}$, M. Jercic${}^{\textrm{\scriptsize 133}}$, R.T. Jimenez Bustamante${}^{\textrm{\scriptsize 100}}$, P.G. Jones${}^{\textrm{\scriptsize 104}}$, A. Jusko${}^{\textrm{\scriptsize 104}}$, P. Kalinak${}^{\textrm{\scriptsize 55}}$, A. Kalweit${}^{\textrm{\scriptsize 34}}$, J.H. Kang${}^{\textrm{\scriptsize 144}}$, V. Kaplin${}^{\textrm{\scriptsize 76}}$, S. Kar${}^{\textrm{\scriptsize 139}}$, A. Karasu Uysal${}^{\textrm{\scriptsize 70}}$, O. Karavichev${}^{\textrm{\scriptsize 52}}$, T. Karavicheva${}^{\textrm{\scriptsize 52}}$, L. Karayan${}^{\textrm{\scriptsize 100}}$,${}^{\textrm{\scriptsize 96}}$, E. Karpechev${}^{\textrm{\scriptsize 52}}$, U. Kebschull${}^{\textrm{\scriptsize 59}}$, R. Keidel${}^{\textrm{\scriptsize 145}}$, D.L.D. Keijdener${}^{\textrm{\scriptsize 53}}$, M. Keil${}^{\textrm{\scriptsize 34}}$, B. Ketzer${}^{\textrm{\scriptsize 44}}$, M. Mohisin Khan${}^{\textrm{\scriptsize 17}}$\Arefidp3246128, P. Khan${}^{\textrm{\scriptsize 103}}$, S.A. Khan${}^{\textrm{\scriptsize 139}}$, A. Khanzadeev${}^{\textrm{\scriptsize 89}}$, Y. Kharlov${}^{\textrm{\scriptsize 114}}$, A. Khatun${}^{\textrm{\scriptsize 17}}$, A. Khuntia${}^{\textrm{\scriptsize 48}}$, M.M. Kielbowicz${}^{\textrm{\scriptsize 120}}$, B. Kileng${}^{\textrm{\scriptsize 36}}$, D. Kim${}^{\textrm{\scriptsize 144}}$, D.W. Kim${}^{\textrm{\scriptsize 42}}$, D.J. Kim${}^{\textrm{\scriptsize 127}}$, H. Kim${}^{\textrm{\scriptsize 144}}$, J.S. Kim${}^{\textrm{\scriptsize 42}}$, J. Kim${}^{\textrm{\scriptsize 96}}$, M. Kim${}^{\textrm{\scriptsize 50}}$, M. Kim${}^{\textrm{\scriptsize 144}}$, S. Kim${}^{\textrm{\scriptsize 19}}$, T. Kim${}^{\textrm{\scriptsize 144}}$, S. Kirsch${}^{\textrm{\scriptsize 41}}$, I. Kisel${}^{\textrm{\scriptsize 41}}$, S. Kiselev${}^{\textrm{\scriptsize 54}}$, A. Kisiel${}^{\textrm{\scriptsize 140}}$, G. Kiss${}^{\textrm{\scriptsize 142}}$, J.L. Klay${}^{\textrm{\scriptsize 6}}$, C. Klein${}^{\textrm{\scriptsize 60}}$, J. Klein${}^{\textrm{\scriptsize 34}}$, C. Klein-Bösing${}^{\textrm{\scriptsize 61}}$, S. Klewin${}^{\textrm{\scriptsize 96}}$, A. Kluge${}^{\textrm{\scriptsize 34}}$, M.L. Knichel${}^{\textrm{\scriptsize 96}}$, A.G. Knospe${}^{\textrm{\scriptsize 126}}$, C. Kobdaj${}^{\textrm{\scriptsize 117}}$, M. Kofarago${}^{\textrm{\scriptsize 34}}$, T. Kollegger${}^{\textrm{\scriptsize 100}}$, A. Kolojvari${}^{\textrm{\scriptsize 138}}$, V. Kondratiev${}^{\textrm{\scriptsize 138}}$, N. Kondratyeva${}^{\textrm{\scriptsize 76}}$, E. Kondratyuk${}^{\textrm{\scriptsize 114}}$, A. Konevskikh${}^{\textrm{\scriptsize 52}}$, M. Kopcik${}^{\textrm{\scriptsize 118}}$, M. Kour${}^{\textrm{\scriptsize 93}}$, C. Kouzinopoulos${}^{\textrm{\scriptsize 34}}$, O. Kovalenko${}^{\textrm{\scriptsize 79}}$, V. Kovalenko${}^{\textrm{\scriptsize 138}}$, M. Kowalski${}^{\textrm{\scriptsize 120}}$, G. Koyithatta Meethaleveedu${}^{\textrm{\scriptsize 47}}$, I. Králik${}^{\textrm{\scriptsize 55}}$, A. Kravčáková${}^{\textrm{\scriptsize 39}}$, M. Krivda${}^{\textrm{\scriptsize 55}}$,${}^{\textrm{\scriptsize 104}}$, F. Krizek${}^{\textrm{\scriptsize 87}}$, E. Kryshen${}^{\textrm{\scriptsize 89}}$, M. Krzewicki${}^{\textrm{\scriptsize 41}}$, A.M. Kubera${}^{\textrm{\scriptsize 18}}$, V. Kučera${}^{\textrm{\scriptsize 87}}$, C. Kuhn${}^{\textrm{\scriptsize 135}}$, P.G. Kuijer${}^{\textrm{\scriptsize 85}}$, A. Kumar${}^{\textrm{\scriptsize 93}}$, J. Kumar${}^{\textrm{\scriptsize 47}}$, L. Kumar${}^{\textrm{\scriptsize 91}}$, S. Kumar${}^{\textrm{\scriptsize 47}}$, S. Kundu${}^{\textrm{\scriptsize 81}}$, P. Kurashvili${}^{\textrm{\scriptsize 79}}$, A. Kurepin${}^{\textrm{\scriptsize 52}}$, A.B. Kurepin${}^{\textrm{\scriptsize 52}}$, A. Kuryakin${}^{\textrm{\scriptsize 102}}$, S. Kushpil${}^{\textrm{\scriptsize 87}}$, M.J. Kweon${}^{\textrm{\scriptsize 50}}$, Y. Kwon${}^{\textrm{\scriptsize 144}}$, S.L. La Pointe${}^{\textrm{\scriptsize 41}}$, P. La Rocca${}^{\textrm{\scriptsize 27}}$, C. Lagana Fernandes${}^{\textrm{\scriptsize 123}}$, I. Lakomov${}^{\textrm{\scriptsize 34}}$, R. Langoy${}^{\textrm{\scriptsize 40}}$, K. Lapidus${}^{\textrm{\scriptsize 143}}$, C. Lara${}^{\textrm{\scriptsize 59}}$, A. Lardeux${}^{\textrm{\scriptsize 20}}$,${}^{\textrm{\scriptsize 65}}$, A. Lattuca${}^{\textrm{\scriptsize 25}}$, E. Laudi${}^{\textrm{\scriptsize 34}}$, R. Lavicka${}^{\textrm{\scriptsize 38}}$, L. Lazaridis${}^{\textrm{\scriptsize 34}}$, R. Lea${}^{\textrm{\scriptsize 24}}$, L. Leardini${}^{\textrm{\scriptsize 96}}$, S. Lee${}^{\textrm{\scriptsize 144}}$, F. Lehas${}^{\textrm{\scriptsize 85}}$, S. Lehner${}^{\textrm{\scriptsize 115}}$, J. Lehrbach${}^{\textrm{\scriptsize 41}}$, R.C. Lemmon${}^{\textrm{\scriptsize 86}}$, V. Lenti${}^{\textrm{\scriptsize 106}}$, E. Leogrande${}^{\textrm{\scriptsize 53}}$, I. León Monzón${}^{\textrm{\scriptsize 122}}$, P. Lévai${}^{\textrm{\scriptsize 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Affiliation notes

{Authlist}

\Adef

0Deceased

\Adef

idp1791728Also at: Dipartimento DET del Politecnico di Torino, Turin, Italy

\Adef

idp1811120Also at: Georgia State University, Atlanta, Georgia, United States

\Adef

idp3246128Also at: Also at Department of Applied Physics, Aligarh Muslim University, Aligarh, India

\Adef

idp4017808Also at: M.V. Lomonosov Moscow State University, D.V. Skobeltsyn Institute of Nuclear, Physics, Moscow, Russia

Collaboration Institutes

1A.I. Alikhanyan National Science Laboratory (Yerevan Physics Institute) Foundation, Yerevan, Armenia

2Benemérita Universidad Autónoma de Puebla, Puebla, Mexico

3Bogolyubov Institute for Theoretical Physics, Kiev, Ukraine

4Bose Institute, Department of Physics and Centre for Astroparticle Physics and Space Science (CAPSS), Kolkata, India

5Budker Institute for Nuclear Physics, Novosibirsk, Russia

6California Polytechnic State University, San Luis Obispo, California, United States

7Central China Normal University, Wuhan, China

8Centre de Calcul de l’IN2P3, Villeurbanne, Lyon, France

9Centro de Aplicaciones Tecnológicas y Desarrollo Nuclear (CEADEN), Havana, Cuba

10Centro de Investigaciones Energéticas Medioambientales y Tecnológicas (CIEMAT), Madrid, Spain

11Centro de Investigación y de Estudios Avanzados (CINVESTAV), Mexico City and Mérida, Mexico

12Centro Fermi - Museo Storico della Fisica e Centro Studi e Ricerche “Enrico Fermi’, Rome, Italy

13Chicago State University, Chicago, Illinois, United States

14China Institute of Atomic Energy, Beijing, China

15COMSATS Institute of Information Technology (CIIT), Islamabad, Pakistan

16Departamento de Física de Partículas and IGFAE, Universidad de Santiago de Compostela, Santiago de Compostela, Spain

17Department of Physics, Aligarh Muslim University, Aligarh, India

18Department of Physics, Ohio State University, Columbus, Ohio, United States

19Department of Physics, Sejong University, Seoul, South Korea

20Department of Physics, University of Oslo, Oslo, Norway

21Department of Physics and Technology, University of Bergen, Bergen, Norway

22Dipartimento di Fisica dell’Università ’La Sapienza’ and Sezione INFN, Rome, Italy

23Dipartimento di Fisica dell’Università and Sezione INFN, Cagliari, Italy

24Dipartimento di Fisica dell’Università and Sezione INFN, Trieste, Italy

25Dipartimento di Fisica dell’Università and Sezione INFN, Turin, Italy

26Dipartimento di Fisica e Astronomia dell’Università and Sezione INFN, Bologna, Italy

27Dipartimento di Fisica e Astronomia dell’Università and Sezione INFN, Catania, Italy

28Dipartimento di Fisica e Astronomia dell’Università and Sezione INFN, Padova, Italy

29Dipartimento di Fisica ‘E.R. Caianiello’ dell’Università and Gruppo Collegato INFN, Salerno, Italy

30Dipartimento DISAT del Politecnico and Sezione INFN, Turin, Italy

31Dipartimento di Scienze e Innovazione Tecnologica dell’Università del Piemonte Orientale and INFN Sezione di Torino, Alessandria, Italy

32Dipartimento Interateneo di Fisica ‘M. Merlin’ and Sezione INFN, Bari, Italy

33Division of Experimental High Energy Physics, University of Lund, Lund, Sweden

34European Organization for Nuclear Research (CERN), Geneva, Switzerland

35Excellence Cluster Universe, Technische Universität München, Munich, Germany

36Faculty of Engineering, Bergen University College, Bergen, Norway

37Faculty of Mathematics, Physics and Informatics, Comenius University, Bratislava, Slovakia

38Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University in Prague, Prague, Czech Republic

39Faculty of Science, P.J. Šafárik University, Košice, Slovakia

40Faculty of Technology, Buskerud and Vestfold University College, Tonsberg, Norway

41Frankfurt Institute for Advanced Studies, Johann Wolfgang Goethe-Universität Frankfurt, Frankfurt, Germany

42Gangneung-Wonju National University, Gangneung, South Korea

43Gauhati University, Department of Physics, Guwahati, India

44Helmholtz-Institut für Strahlen- und Kernphysik, Rheinische Friedrich-Wilhelms-Universität Bonn, Bonn, Germany

45Helsinki Institute of Physics (HIP), Helsinki, Finland

46Hiroshima University, Hiroshima, Japan

47Indian Institute of Technology Bombay (IIT), Mumbai, India

48Indian Institute of Technology Indore, Indore, India

49Indonesian Institute of Sciences, Jakarta, Indonesia

50Inha University, Incheon, South Korea

51Institut de Physique Nucléaire d’Orsay (IPNO), Université Paris-Sud, CNRS-IN2P3, Orsay, France

52Institute for Nuclear Research, Academy of Sciences, Moscow, Russia

53Institute for Subatomic Physics of Utrecht University, Utrecht, Netherlands

54Institute for Theoretical and Experimental Physics, Moscow, Russia

55Institute of Experimental Physics, Slovak Academy of Sciences, Košice, Slovakia

56Institute of Physics, Academy of Sciences of the Czech Republic, Prague, Czech Republic

57Institute of Physics, Bhubaneswar, India

58Institute of Space Science (ISS), Bucharest, Romania

59Institut für Informatik, Johann Wolfgang Goethe-Universität Frankfurt, Frankfurt, Germany

60Institut für Kernphysik, Johann Wolfgang Goethe-Universität Frankfurt, Frankfurt, Germany

61Institut für Kernphysik, Westfälische Wilhelms-Universität Münster, Münster, Germany

62Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Mexico City, Mexico

63Instituto de Física, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, Brazil

64Instituto de Física, Universidad Nacional Autónoma de México, Mexico City, Mexico

65IRFU, CEA, Université Paris-Saclay, F-91191 Gif-sur-Yvette, France, Saclay, France

66iThemba LABS, National Research Foundation, Somerset West, South Africa

67Joint Institute for Nuclear Research (JINR), Dubna, Russia

68Konkuk University, Seoul, South Korea

69Korea Institute of Science and Technology Information, Daejeon, South Korea

70KTO Karatay University, Konya, Turkey

71Laboratoire de Physique Corpusculaire (LPC), Clermont Université, Université Blaise Pascal, CNRS–IN2P3, Clermont-Ferrand, France

72Laboratoire de Physique Subatomique et de Cosmologie, Université Grenoble-Alpes, CNRS-IN2P3, Grenoble, France

73Laboratori Nazionali di Frascati, INFN, Frascati, Italy

74Laboratori Nazionali di Legnaro, INFN, Legnaro, Italy

75Lawrence Berkeley National Laboratory, Berkeley, California, United States

76Moscow Engineering Physics Institute, Moscow, Russia

77Nagasaki Institute of Applied Science, Nagasaki, Japan

78National and Kapodistrian University of Athens, Physics Department, Athens, Greece, Athens, Greece

79National Centre for Nuclear Studies, Warsaw, Poland

80National Institute for Physics and Nuclear Engineering, Bucharest, Romania

81National Institute of Science Education and Research, Bhubaneswar, India

82National Nuclear Research Center, Baku, Azerbaijan

83National Research Centre Kurchatov Institute, Moscow, Russia

84Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark

85Nikhef, Nationaal instituut voor subatomaire fysica, Amsterdam, Netherlands

86Nuclear Physics Group, STFC Daresbury Laboratory, Daresbury, United Kingdom

87Nuclear Physics Institute, Academy of Sciences of the Czech Republic, Řež u Prahy, Czech Republic

88Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States

89Petersburg Nuclear Physics Institute, Gatchina, Russia

90Physics Department, Creighton University, Omaha, Nebraska, United States

91Physics Department, Panjab University, Chandigarh, India

92Physics Department, University of Cape Town, Cape Town, South Africa

93Physics Department, University of Jammu, Jammu, India

94Physics Department, University of Rajasthan, Jaipur, India

95Physikalisches Institut, Eberhard Karls Universität Tübingen, Tübingen, Germany

96Physikalisches Institut, Ruprecht-Karls-Universität Heidelberg, Heidelberg, Germany

97Physik Department, Technische Universität München, Munich, Germany

98Purdue University, West Lafayette, Indiana, United States

99Pusan National University, Pusan, South Korea

100Research Division and ExtreMe Matter Institute EMMI, GSI Helmholtzzentrum für Schwerionenforschung GmbH, Darmstadt, Germany

101Rudjer Bošković Institute, Zagreb, Croatia

102Russian Federal Nuclear Center (VNIIEF), Sarov, Russia

103Saha Institute of Nuclear Physics, Kolkata, India

104School of Physics and Astronomy, University of Birmingham, Birmingham, United Kingdom

105Sección Física, Departamento de Ciencias, Pontificia Universidad Católica del Perú, Lima, Peru

106Sezione INFN, Bari, Italy

107Sezione INFN, Bologna, Italy

108Sezione INFN, Cagliari, Italy

109Sezione INFN, Catania, Italy

110Sezione INFN, Padova, Italy

111Sezione INFN, Rome, Italy

112Sezione INFN, Trieste, Italy

113Sezione INFN, Turin, Italy

114SSC IHEP of NRC Kurchatov institute, Protvino, Russia

115Stefan Meyer Institut für Subatomare Physik (SMI), Vienna, Austria

116SUBATECH, IMT Atlantique, Université de Nantes, CNRS-IN2P3, Nantes, France

117Suranaree University of Technology, Nakhon Ratchasima, Thailand

118Technical University of Košice, Košice, Slovakia

119Technical University of Split FESB, Split, Croatia

120The Henryk Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, Cracow, Poland

121The University of Texas at Austin, Physics Department, Austin, Texas, United States

122Universidad Autónoma de Sinaloa, Culiacán, Mexico

123Universidade de São Paulo (USP), São Paulo, Brazil

124Universidade Estadual de Campinas (UNICAMP), Campinas, Brazil

125Universidade Federal do ABC, Santo Andre, Brazil

126University of Houston, Houston, Texas, United States

127University of Jyväskylä, Jyväskylä, Finland

128University of Liverpool, Liverpool, United Kingdom

129University of Tennessee, Knoxville, Tennessee, United States

130University of the Witwatersrand, Johannesburg, South Africa

131University of Tokyo, Tokyo, Japan

132University of Tsukuba, Tsukuba, Japan

133University of Zagreb, Zagreb, Croatia

134Université de Lyon, Université Lyon 1, CNRS/IN2P3, IPN-Lyon, Villeurbanne, Lyon, France

135Université de Strasbourg, CNRS, IPHC UMR 7178, F-67000 Strasbourg, France, Strasbourg, France

136Università degli Studi di Pavia, Pavia, Italy

137Università di Brescia, Brescia, Italy

138V. Fock Institute for Physics, St. Petersburg State University, St. Petersburg, Russia

139Variable Energy Cyclotron Centre, Kolkata, India

140Warsaw University of Technology, Warsaw, Poland

141Wayne State University, Detroit, Michigan, United States

142Wigner Research Centre for Physics, Hungarian Academy of Sciences, Budapest, Hungary

143Yale University, New Haven, Connecticut, United States

144Yonsei University, Seoul, South Korea

145Zentrum für Technologietransfer und Telekommunikation (ZTT), Fachhochschule Worms, Worms, Germany