System Size and Centrality Dependence of Charged Hadron Transverse Momentum Spectra in Au + Au and Cu + Cu Collisions at (s_(NN))~(1/2) = 62.4 and 200 GeV

摘要

We present transverse momentum distributions of charged hadrons produced in Cu + Cu collisions at (s_(NN))~(1/2) = 62.4 and 200 GeV. The spectra are measured for transverse momenta of 0.25 < p_T < 5.0 GeV/c at (s_(NN))~(1/2) = 62.4 GeV and 0.25 < p_T < 7.0 GeV/c at (s_(NN))~(1/2) = 200 GeV, in a pseudorapidity range of 0.2 < η < 1.4. The nuclear modification factor R_(AA) is calculated relative to p + p data at both collision energies as a function of collision centrality. At a given collision energy and fractional cross section, R_(AA) is observed to be systematically larger in Cu + Cu collisions compared to Au + Au. However, for the same number of participating nucleons, R_(AA) is essentially the same in both systems over the measured range of p_T, in spite of the significantly different geometries of the Cu + Cu and Au + Au systems.