Central-to-peripheral nuclear modification factors in Pb-Pb collisions at √sNN = 17.3 GeV

Abstract We present central-to-peripheral nuclear modification factors, R CP , for the p T distributions of K S 0 , Λ, Λ ¯ , and negatively charged particles, measured at central rapidity in Pb–Pb collisions at top SPS energy. The data cover the 55% most central fraction of the inelastic cross section. The K S 0 and Λ R CP ( p T ) are similar in shape to those measured at s NN = 200 GeV at RHIC, though they are larger in absolute value. We have compared our K S 0 R CP data to a theoretical calculation. The prediction overestimates the data at p T ≈ 3 – 4 GeV / c , unless sizeable parton energy loss is included in the calculation.