Measurement of the Z boson production cross-section in proton-lead collisions at s NN $$ \sqrt{s_{\textrm{NN}}} $$ = 8.16 TeV

Abstract

Abstract

This article presents the first measurement of the differential Z-boson production cross-section in the forward region using proton-lead collisions with the LHCb detector. The dataset was collected at a nucleon-nucleon centre-of-mass energy of

s NN

$$ \sqrt{s_{\textrm{NN}}} $$ = 8.16 TeV in 2016, corresponding to an integrated luminosity of 30.8 nb−1. The forward-backward ratio and the nuclear modification factors are measured together with the differential cross-section as functions of the Z boson rapidity in the centre-of-mass frame, the transverse momentum of the Z boson and a geometric variable ϕ*. The results are in good agreement with the predictions from nuclear parton distribution functions, providing strong constraining power at small Bjorken-x.