The Origin of Large-p_T pi^0 Suppression at RHIC

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  • 7 August 2002
Abstract
We present results for inclusive pi^0 production in proton-proton and in Au-Au at RHIC energy sqrt(s) = 200GeV. We include the full next-to-leading order radiative corrections, O(alpha_s^3), and nuclear effects such as parton energy loss and nuclear shadowing. We find higher-order corrections to be large and p_T dependent and nuclear shadowing effect to be small. We consider the ratio of pi^0 distribution in Au-Au and p-p collisions for p_T > 3 GeV for three cases of parton energy loss: 1) constant parton energy loss per parton scattering, epsilon^a_n = const, 2) Landau-Pemeranchuk-Migdal energy-dependent energy loss, epsilon^a_n ~ sqrt(E^a_n) and 3) Bethe-Heitler energy-dependent energy loss, epsilon^a_n ~ E^a_n. We show that recently observed suppression of pi^0 production in Au-Au collisions at RHIC, which is found to increase with p_T increasing from 3GeV to 8GeV, can be attributed to the parton energy loss, when epsilon^a_n = 0.06 E^a_n. We predict prompt photon production in proton-proton and in Au-Au collisions at RHIC. We show that the ratio of prompt photons to neutral pions produced in Au-Au collisions at RHIC has a strong p_T dependence approaching one at p_T ~ 10GeV.

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