Correlation between mean transverse momentum and multiplicity in p-p collisions at s = 900 GeV in ALICE

The mean transverse momentum 〈pT 〉 of particles produced in heavy ion collisions and its event-by-event fluctuations are considered to be sensitive to critical fluctuations of the temperature of the hot and dense system created in such collisions. Fluctuations of 〈pT 〉 in proton-proton collisions are an essential reference measurement for these studies. Furthermore the mean transverse momentum in itself, and in particular its dependence on the charged particle multiplicity is an important constraint for phenomenological models to describe these collisions at high energies. Here we report how 〈pT 〉 is extracted from the transverse momentum spectra measured by the ALICE Time Projection Chamber in the first run period of the LHC in 2009 in proton-proton collisions at √ s = 900 GeV.