The ATLAS detector at the LHC obtained the sample of p+Pb data at $\sqrt{ s_{ NN}}={ }$5.02TeV with integrated luminosity of 25nb${ }^{ -1}$, which can be compared to the pp data obtained by interpolating pp measurements at $\sqrt{ s}={ }$2.76TeV and 7TeV. 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.
Categories: hep-ex nucl-ex