Study of Z boson production in pp, pPb and PbPb collisions in CMS

Anna Julia Zsigmond

doi:10.1088/1742-6596/612/1/012011

Abstract

The Z boson production is studied in PbPb and pp collisions at = 2.76 TeV and in pPbcollisions at = 5.02 TeV using data collected by the CMS experiment at the LHC. The Z boson production is observed to be proportional to the number of elementary nucleon-nucleon collisions in both PbPb and pPb collisions. The measured differential cross sections as a function of transverse momentum and rapidity are in agreement with NLO pQCD calculations using different parton distribution functions with and without nuclear effects. Using the PbPb and pp data, the nuclear modification factor is presented as well as the forward- backward ratio measured in pPb collisions.

Highlights

Thanks to its high center-of-mass energy and high luminosity, the LHC allows the study of Z and W boson production in heavy ion collisions for the first time
Due to the large statistical uncertainties, this measurement is not able to distinguish between different nuclear PDFs (nPDFs) sets but it can constrain their uncertainties by adding new data points to the global fits in a previously unexplored region of the Q2 − x phase space
CMS showed that Z boson production is unmodified by the hot and dense QCD medium produced in heavy ion collisions, and its yield scales with the number of binary nucleon-nucleon collisions

Summary

Introduction

Thanks to its high center-of-mass energy and high luminosity, the LHC allows the study of Z and W boson production in heavy ion collisions for the first time. The study of Z boson production at sNN = 2.76 TeV is presented using PbPb collision data collected in 2011 corresponding to an integrated luminosity of 150 μb−1 and using pp collision data recorded in 2013 with an integrated luminosity of 5.4 pb−1 [3] These data samples allow for more precise measurement of the Z boson nuclear modification factor (RAA) and its dependence on transverse momentum (pT), rapidity (y) and collision centrality. The results on Z boson production cross section in pPb collisions at sNN = 5.02 TeV corresponding to an integrated luminosity of 34.6 nb−1 are presented [4].

CMS Preliminary

Conclusions