Estudo da produção de $J/\psi$ o experimento ALICE utilizando o calorímetro eletromagnético

This work presents the measurement of the J/ production with pT > 5 GeV/c at midrapidity (|y| < 0.7) with the ALICE experiment in 7 TeV proton-proton collisions, using the electromagnetic calorimeter (EMCal) triggered events. This measurement is very important due to the possibility of studying models that predict the heavy quarkonium production, and it also provides baseline results to be compared with the J/ production in PbPb, where the Quark Gluon Plasma (QGP) is formed. This measurement was separated into 4 pT bins in order to reproduce a J/ pT spectrum. The differential cross section (d2/dpT dy) results achieved were: 0.42 ± 0.11(est.) ± 0.13(sys.) b GeV/c for pT between 5 and 7 GeV/c, 0.18 ± 0.03(est.) ± 0.04(sys.) b GeV/c for pT between 7 and 9 GeV/c, 0.041 ± 0.008(est.) ± 0.008(sys.) b GeV/c for pT 9 and 11 GeV/c and 0,014 ± 0,003(est.) ± 0,005(sis.) b GeV/c for pT between 11 and 14 GeV/c. These values are compatible with Non-Relativistic (NRQCD) and Color Evaporation model (CEM) predictions. Besides, they are also compatible with results from ALICE (low pT ) and with ATLAS results (for pT > 6 GeV/c). This work also shows the measurement of the fraction of non-prompt J/ (fB). The results were: fB = 0,267 ± 0,114 (hpT i = 7,15 GeV/c), fB = 0,338 ± 0,116 (hpT i = 10,7 GeV/c), fB = 0,271 ± 0,087 (hpT i = 8,5 GeV/c), which are compatible with ATLAS results. The last study made in this work was the feasility of the measurement of J/ in Pb-Pb collisions for pT > 6 GeV/c, using the EMCal L1 Gamma trigger. Considering events from the centrality region 20-60%, 93 ± 16 J/s were reconstructed.