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

Understand

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.