Nuclear effects on the transverse momentum spectra of charged particles in pPb Collisions at $\sqrt{s_{NN}}$ = 5.02 TeV

Abstract

Transverse momentum spectra of charged particles are measured by the CMS experiment at the CERN LHC in pPb collisions at sNN−−−√=5.02 TeV , in the range 0.4<pT<120 GeV/c and pseudorapidity |η\textsccm|<1.8 in the proton–nucleon center-of-mass frame. For pT<10 GeV/c , the charged-particle production is asymmetric about η\textsccm=0 , with smaller yield observed in the direction of the proton beam, qualitatively consistent with expectations from shadowing in nuclear parton distribution functions (nPDF). A pp reference spectrum at s√=5.02 TeV is obtained by interpolation 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 calculations that include antishadowing modifications of nPDFs.