Measurement of the Drell--Yan triple-differential cross section in $pp$ collisions at $\sqrt{s} = 8$ TeV

TL;DR

This paper reports a high-precision measurement of the triple-differential Drell--Yan cross section in proton-proton collisions at 8 TeV, providing detailed data for testing the Standard Model and constraining parton distribution functions.

Contribution

It presents the first detailed triple-differential measurement of the Drell--Yan process at 8 TeV, extending the kinematic range and achieving sub-percent precision in the pole region.

Findings

Measurements agree with Standard Model predictions

Data sensitive to parton distribution functions

High-precision asymmetry measurements

Abstract

This paper presents a measurement of the triple-differential cross section for the Drell--Yan process $Z/\gamma^*\rightarrow \ell^+\ell^-$ where $\ell$ is an electron or a muon. The measurement is performed for invariant masses of the lepton pairs, $m_{\ell\ell}$, between $46$ and $200$ GeV using a sample of $20.2$ fb$^{-1}$ of $pp$ collisions data at a centre-of-mass energy of $\sqrt{s}=8$ TeV collected by the ATLAS detector at the LHC in 2012. The data are presented in bins of invariant mass, absolute dilepton rapidity, $|y_{\ell\ell}|$, and the angular variable $\cos\theta^{*}$ between the outgoing lepton and the incoming quark in the Collins--Soper frame. The measurements are performed in the range $|y_{\ell\ell}|<2.4$ in the muon channel, and extended to $|y_{\ell\ell}|<3.6$ in the electron channel. The cross sections are used to determine the $Z$ boson forward-backward asymmetry as a function of $|y_{\ell\ell}|$ and $m_{\ell\ell}$. The measurements achieve high-precision, below the percent level in the pole region, excluding the uncertainty in the integrated luminosity, and are in agreement with predictions. These precision data are sensitive to the parton distribution functions and the effective weak mixing angle.