Measurement of forward $\rm Z\rightarrow e^+e^-$ production at $\sqrt{s}=8$TeV

TL;DR

This paper reports a precise measurement of Z-boson production cross-section in the forward region at 8TeV using LHCb data, providing detailed differential cross-sections as functions of rapidity and angular variables.

Contribution

It presents the first detailed measurement of Z→ee production cross-section in the forward region at 8TeV with high precision and differential distributions.

Findings

Total cross-section measured as 93.81 pb with uncertainties.

Differential cross-sections as functions of rapidity and angular variables.

Results agree with Standard Model predictions.

Abstract

A measurement of the cross-section for Z-boson production in the forward region of pp collisions at 8TeV centre-of-mass energy is presented. The measurement is based on a sample of $\rm Z\rightarrow e^+e^-$ decays reconstructed using the LHCb detector, corresponding to an integrated luminosity of 2.0fb$^{-1}$. The acceptance is defined by the requirements $2.0<\eta<4.5$ and $p_{\rm T}>20$GeV for the pseudorapidities and transverse momenta of the leptons. Their invariant mass is required to lie in the range 60--120GeV. The cross-section is determined to be $$ \sigma({\rm pp\to Z\to e^+e^-})=93.81\pm0.41({\rm stat})\pm1.48({\rm syst})\pm1.14({\rm lumi})\;{\rm pb}\,,$$ where the first uncertainty is statistical and the second reflects all systematic effects apart from that arising from the luminosity, which is given as the third uncertainty. Differential cross-sections are presented as functions of the Z-boson rapidity and of the angular variable $\phi^*$, which is related to the Z-boson transverse momentum.