Transverse-momentum distribution and nuclear modification factor for neutral pions in the forward-rapidity region in proton-lead collisions at s NN =5.02 TeV

The transverse momentum (pT) distribution for inclusive neutral pions in the very forward rapidity region has been measured, with the Large Hadron Collider forward detector (LHCf), in proton-lead collisions at nucleon-nucleon center-of-mass energies of sNN=5.02TeV at the LHC. The pT spectra obtained in the rapidity range -11.0<ylab<-8.9 and 0<pT<0.6GeV (in the detector reference frame) show a strong suppression of the production of neutral pions after taking into account ultraperipheral collisions. This leads to a nuclear modification factor value, relative to the interpolated pT spectra in proton-proton collisions at s=5.02TeV, of about 0.1-0.4. This value is compared with the predictions of several hadronic interaction Monte Carlo simulations. © 2014 CERN, for the LHCf Collaboration.