Electroweak boson production in heavy-ion collisions with CMS

Michael Gardner

doi:10.1088/1742-6596/509/1/012071

Abstract

The Compact Muon Solenoid (CMS) is fully equipped to measure leptonic decays of electroweak probes in the high multiplicity environment of nucleus-nucleus collisions. Electroweak boson production is an important benchmark process at hadron colliders. Precise measurements of W and Z production in heavy-ion collisions can help to constrain nuclear PDFs as well as serve as a standard candle of the initial state in PbPb collisions at the LHC energies. The inclusive and differential measurements of the Z boson yield in the muon and electron decay channel will be presented, establishing that no modification is observed with respect to pp collisions, scaled by the number of incoherent nucleon-nucleon collisions.

Highlights

W and Z bosons were first observe√d by the UA1 and UA2 experiments at CERN thirty years ago in proton-antiproton collisions at s = 540 GeV [1]
Z-boson production is reported in this proceedings with the second set of PbPb collisions that occurred in late 2011 and accounts for 150 μb−1 integrated luminosity
The dimuon channel is analyzed with an improved reconstruction algorithm with respect to Ref. [7], and electrons are used for the first time to reconstruct the Z decays in the heavy-ion environment in Compact Muon Solenoid (CMS) [8]

Summary

Introduction

The increases in statistics of both the pp and PbPb samples allow more detailed study of the transverse momentum (pT ), rapidity (y) and collision centrality dependencies of the Z-boson yields. [7], a new muon offline reconstruction algorithm is used for the PbPb data, with increased efficiency due to an improvement in the track reconstruction. These selection criteria further reject about 2% of real muons for both pp and PbPb collisions.

Results

Conclusion