Scaling of charged particle production and centrality determination in p-Pb collisions at √sNN= 5.02 TeV at ALICE

C. Oppedisano, L. Bravina, Y. Foka, S. Kabana
2015 EPJ Web of Conferences  
Proton-nucleus collisions are studied in order to disentangle initial state effects, already present in cold nuclear matter, from final state effects, that are associated to the hot and strongly interacting medium created in A-A collisions. However, after the 2013 p-Pb data taking at LHC, the importance of p-A collisions on their own has been acknowledged. Several measurements clearly showed that p-A collisions cannot simply be explained by an incoherent superposition of proton-nucleon
more » ... on-nucleon collisions, but indicate the presence of coherent and collective effects, with a strong dependence on the collision geometry. These measurements pointed out the need for a detailed characterization of the collision geometry. Typically, parameters such as the number of binary collisions N coll or the number of participating nucleons N part are used to characterize the centrality. In nucleus-nucleus interactions the centrality is usually estimated by measuring the charged particle multiplicity. However, in contrast to A-A, in p-A collisions the large fluctuations in a much reduced multiplicity environment generate a dynamical bias in centrality classes based on particle multiplicity measurement. The centrality determination is critically addressed and a different approach to extract the average N coll values, needed to compare p-A to pp data, is presented. The centrality dependence of primary charged-particle production and of transverse momentum distributions in p-A collisions at √ s NN = 5.02 TeV measured by ALICE are presented. 7KLV LV DQ 2SHQ $FFHVV DUWLFOH GLVWULEXWHG XQGHU WKH WHUPV RI WKH &UHDWLYH &RPPRQV $WWULEXWLRQ /LFHQVH ZKLFK SHUPLWV XQUHVWULFWHG XVH GLVWULEXWLRQ DQG UHSURGXFWLRQ LQ DQ\ PHGLXP SURYLGHG WKH RULJLQDO ZRUN LV SURSHUO\ FLWHG 7 7 Article available at
doi:10.1051/epjconf/20159504047 fatcat:lq5ebps6rjc5hmigzroesixemy