Measurements of charged particle spectra and nuclear modification factor in p+Pb collisions with the ATLAS detector

The ATLAS detector at the LHC obtained the sample of p  +Pb data at sNN=5.02 TeV with integrated luminosity of 25 nb−1, which can be compared to the pp data obtained by interpolating pp   measurements at s=2.76 TeV and 7 TeV. Due to the excellent capabilities of the ATLAS detector, and its stable operation in heavy ion as well as proton–proton physics runs, the data allow measurements of the nuclear modification factor, ratio of heavy ion charged particle spectra divided by pp reference, in different centrality classes over a wide range of rapidity. The charged particle nuclear modification factor is found to vary significantly as a function of transverse momentum with a stronger dependence in more peripheral collisions.