New single- and double-parton scattering mechanisms for double charmed meson production

TL;DR

This paper introduces new single- and double-parton scattering mechanisms for double charmed meson production, comparing theoretical predictions with LHCb experimental data and highlighting the impact of scale-dependent fragmentation functions.

Contribution

It proposes novel SPS and DPS mechanisms for double $D^{0}$ production, incorporating scale-dependent fragmentation functions and analyzing their effects on observed distributions.

Findings

New SPS mechanism involving $gg$ production and $g o D^{0}$ fragmentation.

Scale-dependent fragmentation functions significantly alter production predictions.

Theoretical results align better with experimental data when including new mechanisms.

Abstract

We discuss charm meson-meson pair production recently observed by the LHCb Collaboration at $\sqrt{s}$ = 7 TeV in proton-proton scattering. We examine double-parton scattering (DPS) mechanisms of double $c \bar c$ production and following $cc \to D^{0}D^{0}$ hadronization as well as double $g$ and mixed $g c\bar c $ production with $gg \to D^{0}D^{0}$ and $gc \to D^{0}D^{0}$ hadronization calculated with the help of the scale-dependent KKKS08 fragmentation functions. A new single-parton scattering (SPS) mechanism of $gg$ production is also taken into consideration. Calculated differential distributions as a function of transverse momentum $p_{T}$ of one of the $D^{0}$ mesons, pair invariant mass $M_{D^{0}D^{0}}$ and azimuthal angle $\varphi_{D^{0}D^{0}}$ distributions are confronted with the measured ones. The manifestation of the new SPS mechanisms with $g \to D^{0}$ fragmentation within the scale-dependent fragmentation scheme change the overall picture suitable for standard scale-independent fragmentation where only DPS $cc \to D^{0}D^{0}$ mechanism is present. Some consequences of the new mechanisms are discussed