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Measurement of D+s production and nuclear modification factor in Pb-Pb collisions at √sNN=2.76 TeV

The production of prompt D+s mesons was measured for the first time in collisions of heavy nuclei with the ALICE detector at the LHC. The analysis was performed on a data sample of Pb-Pb collisions at a centre-of-mass energy per nucleon pair, √sNN, of 2.76 TeV in two different centrality classes, namely 0-10% and 20-50%. D+s mesons and their antiparticles were reconstructed at mid-rapidity from their hadronic decay channel D+s→ϕπ+, with ϕ→K−K+, in the transverse momentum intervals 4< pT< 12 GeV/c and 6< pT< 12 GeV/c for the 0-10% and 20- 50% centrality classes, respectively. The nuclear modification factor RAA was computed by comparing the pT-differential production yields in Pb-Pb collisions to those in proton-proton (pp) collisions at the same energy. This pp reference was obtained using the cross section measured at √s=7 TeV and scaled to √s=2.76 TeV. The RAA of D+s mesons was compared to that of non-strange D mesons in the 10% most central Pb-Pb collisions. At high pT (8< pT< 12 GeV/c) a suppression of the D+s-meson yield by a factor of about three, compatible within uncertainties with that of non- strange D mesons, is observed. At lower pT (4< pT< 8 GeV/c) the values of the D+s-meson RAA are larger than those of non-strange D mesons, although compatible within uncertainties. The production ratios D+s/D0 and D+s\D+ were also measured in Pb-Pb collisions and compared to their values in proton-proton collisions.

D-meson ; nuclear modification factor ; lead-lead

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