Transverse momentum spectra of charged particles are measured by the CMS experiment at the CERN LHC in pPb collisions at sqrt(s[NN]) = 5.02 TeV, in the range 0.4 < pt < 120 GeV and pseudorapidity abs(eta[CM]) < 1.8 in the proton-nucleon center-of-mass frame. For pt < 10 GeV, the charged-particle production is asymmetric about eta[CM] = 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 sqrt(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 compared to expectations from the pp reference. The enhancement is larger than predicted by perturbative quantum chromodynamics calculations that include antishadowing modifications of nPDFs.
Nuclear effects on the transverse momentum spectra of charged particles in pPb collisions at a nucleon-nucleon center-of-mass energy of 5.02 TeV
CAVALLO, Nicola;FABOZZI, FRANCESCO;
2015-01-01
Abstract
Transverse momentum spectra of charged particles are measured by the CMS experiment at the CERN LHC in pPb collisions at sqrt(s[NN]) = 5.02 TeV, in the range 0.4 < pt < 120 GeV and pseudorapidity abs(eta[CM]) < 1.8 in the proton-nucleon center-of-mass frame. For pt < 10 GeV, the charged-particle production is asymmetric about eta[CM] = 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 sqrt(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 compared to expectations from the pp reference. The enhancement is larger than predicted by perturbative quantum chromodynamics calculations that include antishadowing modifications of nPDFs.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.