Multiplicity dependence of charged pion, kaon, and (anti)proton production at large transverse momentum in p-Pb collisions at $\mathbf{\sqrt{{\textit s}_{\rm NN}}}$ = 5.02 TeV

Submission Date: 
14/01/2016
Article Information
Submission Form
System: 
p-Pb
Energy: 
5.02 TeV
Abstract Plain Text: 

The production of charged pions, kaons, and (anti)protons at mid-rapidity ($0 < y_{\rm cms} < 0.5$) in p-Pb collisions at $\sqrt{s_{\rm NN}}\,=5.02$ TeV has been measured using the ALICE detector at the LHC. Exploiting the capabilities of the High Momentum Particle Identification Detector and the Time Projection Chamber, the transverse momentum ($p_{\rm T}$) spectra have been extracted up to 20 GeV/$c$ for non single diffractive (NSD) events and for seven multiplicity classes. The pp reference spectra at $\sqrt{s}=$ 5.02 TeV have been constructed as needed for the calculation of the nuclear modification factor ($R_{\rm pPb}$)  in NSD p-Pb collisions. For this, the $p_{\rm T}$ spectra in inelastic pp collisions at $\sqrt{s}=7$ TeV have been expended up to 20 GeV/$c$. 

At intermediate $p_{\rm T}$, the (anti)proton $R_{\rm pPb}$ shows a Cronin-like peak, while pions and kaons show no nuclear modification at intermediate and high $p_{\rm T}$ within systematic and statistical uncertainties. The $p_{\rm T}$ differential particle ratios are reported as a function of the event multiplicity. At intermediate $p_{\rm T}$, $2 < p_{\rm T} < 10$ GeV/$c$, the proton-to-pion ratio exhibits an enhancement which increases with the multiplicity. The $p_{\rm T}$ dependent structure of this increase is qualitatively similar to the increase observed in heavy ion collisions. The multiplicity dependence is not observed at high $p_{\rm T}$, $p_{\rm T} > 10$ GeV/$c$, where the results are found to be independent of system size.

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