Measurement of Z boson Production in Pb+Pb Collisions at sqrt(s_NN)=2.76 TeV with the ATLAS Detector

TL;DR

This paper reports the measurement of Z boson production in lead-lead collisions at 2.76 TeV using the ATLAS detector, showing yield proportionality to binary collisions and no significant azimuthal anisotropy.

Contribution

First measurement of Z boson production in Pb+Pb collisions at this energy with detailed yield and anisotropy analysis.

Findings

Z boson yield proportional to binary collision number

No significant azimuthal anisotropy observed

Consistent results across decay channels

Abstract

The ATLAS experiment has observed 1995 Z boson candidates in data corresponding to 0.15 inverse nb of integrated luminosity obtained in the 2011 LHC Pb+Pb run at sqrt(s_NN)=2.76 TeV. The Z bosons are reconstructed via di-electron and di-muon decay channels, with a background contamination of less than 3%. Results from the two channels are consistent and are combined. Within the statistical and systematic uncertainties, the per-event Z boson yield is proportional to the number of binary collisions estimated by the Glauber model. The elliptic anisotropy of the azimuthal distribution of the Z boson with respect to the event plane is found to be consistent with zero.