Nuclear effects on the transverse momentum spectra of charged particles in pPb collisions at sqrt(s_NN) = 5.02 TeV

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 |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, 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.