Transverse momentum distribution and nuclear modification factor of charged particles in p-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV

TL;DR

This paper measures the transverse momentum distribution of charged particles in p-Pb collisions at 5.02 TeV, finding no significant initial-state effects on high-$p_T$ hadron suppression observed in Pb-Pb collisions.

Contribution

It provides the first detailed measurement of $p_T$ spectra and nuclear modification factor in p-Pb collisions at this energy, clarifying the origin of high-$p_T$ suppression.

Findings

$R_{pPb}$ is consistent with unity above 2 GeV/$c$

No significant pseudorapidity dependence of $p_T$ spectra

High-$p_T$ suppression in Pb-Pb is not due to initial-state effects

Abstract

The transverse momentum ($p_{\mathrm T}$) distribution of primary charged particles is measured in minimum bias (non-single-diffractive) p-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV with the ALICE detector at the LHC. The $p_{\mathrm T}$ spectra measured near central rapidity in the range $0.5<p_{\mathrm T}<20$ GeV/$c$ exhibit a weak pseudorapidity dependence. The nuclear modification factor $R_{\mathrm{pPb}}$ is consistent with unity for $p_{\mathrm T}$ above 2 GeV/$c$. This measurement indicates that the strong suppression of hadron production at high $p_{\mathrm T}$ observed in Pb-Pb collisions at the LHC is not due to an initial-state effect. The measurement is compared to theoretical calculations.