Measurement of D-s(+) product ion and nuclear modification factor in Pb-Pb collisions at root S-NN=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, root s(NN), 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(+) -> phi pi(+), with phi -> K-K+, in the transverse momentum intervals 4 < p(T) < 12 GeV/c and 6 < p(T) < 12 GeV/c for the 0-10% and 20-50% centrality classes, respectively. The nuclear modi fication factor R-AA was computed by comparing the p(T)-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 root s = 7 TeV and scaled to root s = 2.76TeV. The R-AA of D-s(+) mesons was compared to that of non-strange D mesons in the 10% most central Pb-Pb collisions. At high p(T) (8 < p(T) < 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 p(T) (4 < p(T) < 8 GeV/c) the values of the D-s(+)-meson R-AA are larger than those of non-strange D mesons, although compatible within uncertainties. The production ratios D-s(+)/D-0 and D-s(+)/D+ were also measured in Pb-Pb collisions and compared to their values in proton-proton collisions.