Response of Charged Hadrons to a Coulomb Potential in Heavy-Ion Collisions at the RHIC

Abstract

Response of Charged Hadrons to a Coulomb Potential in Heavy-Ion Collisions at the RHIC Byungsik Hong Department of Physics, Korea University, Seoul 136-701 (Received 27 August 2007, in nal form 19 November 2007) We have analyzed the charged hadron spectra at the Relativistic Heavy Ion Collider (RHIC) in terms of the Coulomb interaction between the hadrons and the thermally expanding reball. Fitting the pion, kaon, and proton spectra simultaneously by using the boost-invariant thermal blast wave formula gives a common kinetic freeze-out temperature of 130 MeV and an expansion velocity of 0.67c, which are quite di erent from the previous estimates. Considering the Coulomb interaction, the yield ratios of negative to positive hadrons are expected to increase signi cantly in the low-momentum region. For the published hadron spectra at the RHIC, we determine the upper limit of the magnitude for the Coulomb potential as 10 MeV. Such a relatively small value of the Coulomb potential is consistent with the large nuclear transparency observed at the RHIC. PACS numbers: 25.75.Dw, 25.75.Ld