Nuclear effects on the transverse momentum spectra of charged particles in pPb collisions at ... formula ...... formula ...

摘要

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.