Hadronic resonances in pp, p–Pb and Pb–Pb in ALICE

Università degli Studi and INFN - Sez. di Bologna

^a e-mail: fbellini@cern.ch

Published online: 22 June 2015

Abstract

The production of hadronic resonances has been measured by the ALICE experiment at mid-rapidity in different collision systems (pp, p–Pb, and Pb–Pb). The measurements of K(892)^*0 and ø(1020) production in Pb–Pb collisions at √s_NN = 2.76 TeV and in pp at √s = 2.76 and 7 TeV are complemented by the more recent measurement in p–Pb collisions at √s_NN = 5.02 TeV. The ratios of resonance to long lived hadron production in the three collision systems are compared in order to investigate re-scattering effects, which appear to be relevant for K^*0 in the most central Pb–Pb collisions, while ø behaves instead like a long-lived particle. Resonance observables contribute to draw the picture of central Pb–Pb collisions as a hydrodynamics-driven system. The comparison of the ø/p and p/π ratios as a function of transverse momentum (p_T) indicates that the mass of the particle determines the spectral shapes at low and intermediate p_T in central Pb–Pb collisions. The mean transverse momentum, 〈p_T〉, of K^*0 and ø in central Pb–Pb collisions is consistent with that of the proton, which has similar mass. In pp and p–Pb collisions the 〈p_T〉 of resonances does not follow mass ordering. The nuclear modification factors (R_AA, R_pA) of the ø meson are also discussed in comparison with those of the stable hadrons.