Abstract
Abstract:
ATLAS measurements of the production of muons from heavy-flavor decays in √sNN =
2.76 TeV Pb+Pb collisions and √s = 2.76 TeV pp collisions at the LHC are presented.
Integrated luminosities of 0.14 nb−1 and 570 nb−1 are used for the Pb+Pb and pp mea- surements,
respectively, which are performed over the muon transverse momentum range 4 < pT < 14 GeV and for
five Pb+Pb centrality intervals. Backgrounds arising from in-flight pion and kaon decays, hadronic
showers, and mis-reconstructed muons are statistically re- moved using a template-fitting
procedure. The heavy-flavor muon differential cross-sections and per-event yields are measured in
pp and Pb+Pb collisions, respectively. The nuclear modification factor RAA obtained from these is
observed to be independent of pT, within un- certainties, and to be less than unity, which
indicates suppressed production of heavy-flavor muons in Pb+Pb collisions. For the 10% most central
Pb+Pb events, the measured RAA is approximately 0.35. The azimuthal modulation of the heavy-flavor
muon yields is also measured and the associated Fourier coefficients vn for n=2, 3 and 4 are given
as a function of pT and centrality. They vary slowly with pT and show a systematic variation with
centrality which is characteristic of other anisotropy measurements, such as that observed for
inclusive hadrons. The measured RAA and vn values are also compared with theoretical calculations.