Nuclear effects on the transverse momentum spectra of charged particles in pPb collisions at √sNN=5.02 TeV

Khachatryan, V. and Sirunyan, A. M. and Tumasyan, A. and Adam, W. and Bergauer, T. and Filipovic, Nicolas and Bencze, György and Hajdu, Csaba and Hidas, Pál and Horváth, Dezső and Siklér, Ferenc and Veszprémi, Viktor and Vesztergombi, György and Zsigmond, Anna Júlia and Karancsi, János and Molnár, József and Pálinkás, József and Makovec, Alajos and Trócsányi, Zoltán and Ujvári, Balázs and Veres, Gábor (2015) Nuclear effects on the transverse momentum spectra of charged particles in pPb collisions at √sNN=5.02 TeV. EUROPEAN PHYSICAL JOURNAL C, 75 (5). ISSN 1434-6044

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Abstract

Transverse momentum spectra of charged particles are measured by the CMS ex- periment at the CERN LHC in pPb collisions at √sNN = 5.02 TeV, in the range 0.4 < pT < 120 GeV/c and pseudorapidity |ηCM | < 1.8 in the proton-nucleon center- of-mass frame. For pT < 10 GeV/c, the charged-particle production is asymmetric about ηCM = 0, with smaller yield observed in the direction of the proton beam, qual- itatively consistent with expectations from shadowing in nuclear parton distribution functions (nPDF). A pp reference spectrum at √s = 5.02 TeV is obtained by inter- polation from previous measurements at higher and lower center-of-mass energies. The pT distribution measured in pPb collisions shows an enhancement of charged particles with pT > 20 GeV/c compared to expectations from the pp reference. The enhancement is larger than predicted by perturbative quantum chromodynamics cal- culations that include antishadowing modifications of nPDFs.

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