Transverse momentum distribution of charged particles and identified hadrons in p-Pb collisions at the LHC with ALICE

Abstract

Hadron production has been measured at mid-rapidity by the ALICE experiment at the LHC in proton-lead (p-Pb) collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV. The transverse momentum ($p_{\mathrm{T}}$) distribution of primary charged particles and of identified light-flavoured hadrons (${\pi }^{\pm }$, K${}^{\pm }$, K${}_{\mathrm{S}}^0$, p, $\bar{\mathrm{p}}$, $\Lambda$, $\bar{\Lambda }$) are presented in this report. Charged-particle tracks are reconstructed in the central barrel over a wide momentum range. Furthermore they can be identified by exploiting specific energy loss (d$E$/d$x$), time-of-flight and topological particle-identification techniques. Particle-production yields, spectral shapes and particle ratios are measured in several multiplicity classes and are compared with results obtained in Pb-Pb collisions at the LHC. The measurement of charged-particle transverse momentum spectra and nuclear modification factor R${}_{\mathrm{pPb}}$ indicates that the strong suppression of high-$p_{\mathrm{T}}$ hadrons observed in Pb-Pb collisions is not due to initial-state effects, but it is rather a fingerprint of jet quenching in hot QCD matter. The systematic study of the hadronic spectral shapes as a function of the particle mass and of particle ratios as a function of charged-particle density provides insights into collective phenomena, as observed in Pb-Pb collisions. Similar features, that could be present in high-multiplicity p-Pb collisions, will also be discussed.

arXiv comment7 pages, 5 figures, presented at the The European Physical Society Conference on High Energy Physics - EPS-HEP2013, 18-24 July 2013, Stockholm, Sweden