Speaker
Description
ATLAS measurements are presented on the production of muons from heavy-flavor decays in $\sqrt{s_{\mathrm{NN}}}$ = 2.76 TeV Pb+Pb collisions and $\sqrt{s}$ = 2.76 TeV $pp$ collisions at the LHC. The measurements are performed over the transverse momentum range 4 <$p_{\mathrm {T}}$< 14 GeV and over the 0-60% centrality interval. Backgrounds arising from in-flight pion and kaon decays, hadronic showers, and mis-reconstructed muons are removed using a template-fit 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 $R_{\mathrm{AA}}$ is observed to be independent of $p_{\mathrm{T}}$ within uncertainties and to be less than unity, which indicates suppressed production of heavy flavor muons in Pb+Pb collisions. The heavy-flavor muon yield is also measured as a function of the azimuthal angle difference, $\phi-Psi_{2}$, relative to the second-order event plane angle. Fourier coefficients associated with the $\cos(2(\phi-\Psi_{2}))$ modulation, $v_2$ , are measured as a function of $p_{\mathrm{T}}$ and centrality. They vary slowly with $p_\mathrm{T}$ and show a systematic variation with centrality that is characteristic of other $v_2$ measurements. The higher-order harmonics $v_3$ and $v_4$ are also measured. These measurements provide insight into the energy loss mechanism of heavy quarks as they propagate through the hot, dense medium produced in heavy ion collisions.
| Preferred Track | Open Heavy Flavors |
|---|---|
| Collaboration | ATLAS |
