Abstract
Measurements of the transverse momentum spectra of light flavor particles at intermediate and high pT are an important tool for QCD studies. In pp collisions they provide a baseline for perturbative QCD, while in Pb-Pb they are used to investigate the suppression caused by the surrounding medium. In p-Pb collisions, such measurements provide a reference to disentangle final from initial state effects and thus play an important role in the search for signatures of the formation of a deconfined hot medium. While the comparison of the p-Pb and Pb-Pb data indicates that initial state effects do not play a role in the suppression of hadron production observed at high pT in heavy ion collisions, several measurements of particle production in the low and intermediate pT region indicate the presence of collective effects.
Highlights
The p–Pb physics program has developed from crucial control-experiment to study cold nuclear effects and to establish a baseline for Pb–Pb to an area where to find groundbreaking discoveries and new challenges.Nuclear modification factors measured by ALICE in minimum bias (MB) p–Pb collisions for charged particles [1], heavy flavor and jets show no deviations from unity at high-pT, demonstrating that the observed strong suppression in Pb–Pb collisions is due to final state effects
The zero-degree energy is related to the number of the slow nucleons emitted in the nucleus fragmentation process, which we model with a Slow Nucleon Model (SNM) [7]
For each V0A distribution selected by ZNA, we find the Ncoll distribution that, convolved with the NBDMB, fits the data, i.e. the parameters of the fit are the relative contributions of each Ncoll bin
Summary
The p–Pb physics program has developed from crucial control-experiment to study cold nuclear effects and to establish a baseline for Pb–Pb to an area where to find groundbreaking discoveries and new challenges. By selecting high (low) multiplicity one chooses large (small) average Npart and positive (negative) multiplicity fluctuations per nucleon-nucleon collision. Other types of biases have an influence on the nuclear modification factor: the jet-veto effect, due to the trivial correlation between the centrality estimator and the presence of a high-pT particles originating from jets in the event; the geometric bias, resulting from the mean impact parameter between nucleons rising for the most peripheral events [9]
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