rho^0 Production and Possible Modification in Au+Au and p+p Collisions at sqrt(s_NN) = 200 GeV

Abstract

We report results on rho(770)^0 -> pi+pi- production at midrapidity in p+p and peripheral Au+Au collisions at sqrt(s_NN) = 200 GeV. This is the first direct measurement of rho(770)^0 -> pi+pi- in heavy-ion collisions. The measured rho^0 peak in the invariant mass distribution is shifted by ~40 MeV/c^2 in minimum bias p+p interactions and ~70 MeV/c^2 in peripheral Au+Au collisions. The rho^0 mass shift is dependent on transverse momentum and multiplicity. The modification of the rho^0 meson mass, width, and shape due to phase space and dynamical effects are discussed.

6 pages, 4 figures, as accepted for Phys. Rev. Lett. The data tables are at http://www.star.bnl.gov/central/publications/pubDetail.php?id=26