J/psi Elliptic Flow in Pb-Pb Collisions at root s(NN)=5.02 TeV

We report a precise measurement of the J/psi elliptic flow in Pb-Pb collisions at root s(NN) = 5.02 TeV with the ALICE detector at the LHC. The J/psi mesons are reconstructed at midrapidity (|y| < 0.9) in the dielectron decay channel and at forward rapidity (2.5 < y < 4.0) in the dimuon channel, both down to zero transverse momentum. At forward rapidity, the elliptic flow v(2) of the J/psi is studied as a function of the transverse momentum and centrality. A positive v(2) is observed in the transverse momentum range 2<p(T)<8GeV/c in the three centrality classes studied and confirms with higher statistics our earlier results at root s(NN) = 2.76 TeV in semicentral collisions. At midrapidity, the J/psi v(2) is investigated as a function of the transverse momentum in semicentral collisions and found to be in agreement with the measurements at forward rapidity. These results are compared to transport model calculations. The comparison supports the idea that at low p(T) the elliptic flow of the J/psi originates from the thermalization of charm quarks in the deconfined medium but suggests that additional mechanisms might be missing in the models

phi meson production at forward rapidity in Pb-Pb collisions at root s(NN)=2.76 TeV

\u3c6 meson measurements provide insight into strangeness production, which is one of the key observables for the hot medium formed in high-energy heavy-ion colli- sions. ALICE measured \u3c6 production through its decay in muon pairs in Pb\u2013Pb collisions at 1asNN = 2.76 TeV in the intermediate transverse momentum range 2 < pT < 5 GeV/c and in the rapidity interval 2.5 < y < 4. The \u3c6 yield was measured as a function of the transverse momen- tum and collision centrality. The nuclear modification factor was obtained as a function of the average number of par- ticipating nucleons. Results were compared with the ones obtained via the kaon decay channel in the same pT range at midrapidity. The values of the nuclear modification factor in the two rapidity regions are in agreement within uncertain- ties

Transverse momentum spectra and nuclear modification factors of charged particles in pp, p-Pb and Pb-Pb collisions at the LHC

We report the measured transverse momentum (pT) spectra of primary charged particles from pp, p-Pb and Pb-Pb collisions at a center-of-mass energy 1asNN = 5.02 TeV in the kinematic range of 0.15 < pT < 50 GeV/c and |\u3b7| < 0.8. A significant improvement of systematic uncertainties motivated the reanalysis of data in pp and Pb-Pb collisions at 1asNN = 2.76 TeV, as well as in p-Pb collisions at 1asNN = 5.02 TeV, which is also presented. Spectra from Pb-Pb collisions are presented in nine centrality intervals and are compared to a reference spectrum from pp collisions scaled by the number of binary nucleon-nucleon collisions. For central collisions, the pT spectra are suppressed by more than a factor of 7 around 6\u20137 GeV/c with a significant reduction in suppression towards higher momenta up to 30 GeV/c. The nuclear modification factor RpPb, constructed from the pp and p-Pb spectra measured at the same collision energy, is consistent with unity above 8 GeV/c. While the spectra in both pp and Pb-Pb collisions are substantially harder at 1asNN = 5.02TeV compared to 2.76 TeV, the nuclear modification factors show no significant collision energy dependence. The obtained results should provide further constraints on the parton energy loss calculations to determine the transport properties of the hot and dense QCD matter