J/psi production in p-p and in Heavy Ions in ATLAS

The inclusive production of the J/Psi meson in its dimuon decay mode is studied in the proton-proton collisions at center-of-mass energy 7 TeV with 2.4 pb-1 daa accumulated by ATLAS during April to August 2010 operation. The double differential cross section is measured with respect to the transverse momentum and rapidity of the J/Psi. The fraction of J/Psi mesons produced from B-hadron decays is also measured as a function of J/Psi transverse momentum and rapidity, and is used to determine the differential cross section for prompt and non-prompt J/Psi, separately. Using the ATLAS detector, a centrality-dependent suppression has been observed in the yield of J/Psi dimuons produced in the collisions of lead ions at a nucleon-nucleon center of mass energy 2.76 TeV, corresponding to an integrated luminosity of ~6.7 ub-1 accumulated in Nov 2010.