J/ψ measurements in 7 TeV p-p collisions with ALICE using EMCal-triggered events

Abstract

J/ψ measurements can be performed with the ALICE experiment through the dilepton decay into e−e+ (for rapidity |y|<0.9) and μ−μ+ (for rapidity −4.0<y<−2.5) pairs, in protonproton, proton-nucleus and nucleus-nucleus collisions. Proton-proton collisions are specially important for the ALICE physics program, since they provide baseline results to be compared with Pb-Pb, where one expects the production of the Quark Gluon Plasma (QGP). Moreover, these measurements are interesting per se because the mechanism of charmonium production in hadron interactions is not yet fully understood. The ALICE Eletromagnetic Calorimeter (EMCal) pT extends the range of J/ψ measurements, since it provides electron/hadron discrimination for higher pT values in comparison to other electron PID techniques in ALICE. The EMCal can also provide fast triggers for events containing high energy electrons. In 2011, during proton-proton collisions at 7 TeV, the ALICE EMCal trigger was intensively used for event selection of showers above 4.8 GeV. In this work, some results from 2011 proton-proton collisions are presented, showing a J/ψ measurement for transversal momentum above 6 GeV/c, due to a combination of the ALICE EMCal PID and trigger system.