Quenching of photon and pion spectra at intermediate RHIC energy

Single prompt photon and pion spectra in p–p and Au–Au collisions at intermediate RHIC energy, √ s NN = 62.4 GeV, are computed at large p ⊥ in perturbative QCD. Next-to-leading order calculations in p–p scattering are first presented. The quenching of the prompt photon and pion yield due to energy loss processes in central Au–Au with respect to p–p collisions is then predicted. At this energy, the small phase-space available to produce hard partons makes the pion quenching almost as pronounced as at √ s NN = 200 GeV, despite the smaller gluon density of the produced medium. In the photon sector, energy loss effects prove small because of this very phase-space restriction, which favours the direct production channel. A significant suppression of high-p ⊥ photons is however predicted, because of a strong isospin effect together with the depletion of nuclear parton densities at large x.