Spin alignment measurements of the K*o(892) and φ(1020) vector mesons in heavy ion collisions at √sNN=200 GeV

Abstract

We present the first spin alignment measurements for the K 0(892) and (1020) vector mesons produced at mid-rapidity with transverse momenta up to 5GeV/c at √sNN = 200GeV at RHIC. The diagonal spin density matrix elements with respect to the reaction plane in Au+Au collisions are 00 = 0.32 ± 0.04 (stat) ± 0.09 (syst) for the K 0 (0.8 <pT <5.0 GeV/c) and 00 = 0.34 ± 0.02 (stat) ± 0.03 (syst) for the (0.4 <pT <5.0 GeV/c), and are constant with transverse momentum and collision centrality. The data are consistent with the unpolarized expectation of 1/3 and thus no evidence is found for the transfer of the orbital angular momentum of the colliding system to the vector meson spins. Spin alignments for K 0 and in Au+Au collisions were also measured with respect to the particle’s production plane.