Study of Z boson production in PbPb collisions at nucleon-nucleon centre of mass energy = 2.76 TeV

TL;DR

This study measures Z boson production in lead-lead collisions at the LHC, analyzing muon decay channels to compare experimental results with theoretical QCD predictions.

Contribution

First measurement of Z boson yields in PbPb collisions at 2.76 TeV, including rapidity, transverse momentum, and centrality dependencies, matching theoretical models.

Findings

Observed Z boson yield per event: (33.8 +/- 5.5 (stat) +/- 4.4 (syst)) x 10^{-8}

Results agree with next-to-leading order QCD calculations scaled by nucleon-nucleon collisions

Measured dependencies on rapidity, transverse momentum, and collision centrality

Abstract

A search for Z bosons in the mu^+mu^- decay channel has been performed in PbPb collisions at a nucleon-nucleon centre of mass energy = 2.76 TeV with the CMS detector at the LHC, in a 7.2 inverse microbarn data sample. The number of opposite-sign muon pairs observed in the 60--120 GeV/c^2 invariant mass range is 39, corresponding to a yield per unit of rapidity (y) and per minimum bias event of (33.8 +/- 5.5 (stat) +/- 4.4 (syst)) 10^{-8}, in the |y|<2.0 range. Rapidity, transverse momentum, and centrality dependencies are also measured. The results agree with next-to-leading order QCD calculations, scaled by the number of incoherent nucleon-nucleon collisions.