Spin alignment measurements of theK*0(892)andϕ(1020)vector mesons in heavy ion collisions atsNN=200GeV

B. I. Abelev, M. M. Aggarwal, Z. Ahammed, B. D. Anderson, D. Arkhipkin, G. S. Averichev, Y. Bai, J. Balewski, O. Barannikova, L. S. Barnby, J. Baudot, S. Baumgart (+360 others)
2008 Physical Review C  
We present the first spin alignment measurements for the K^*0(892) and ϕ(1020) vector mesons produced at mid-rapidity with transverse momenta up to 5 GeV/c at √(s_NN) = 200 GeV at RHIC. The diagonal spin density matrix elements with respect to the reaction plane in Au+Au collisions are ρ_00 = 0.32 ± 0.04 (stat) ± 0.09 (syst) for the K^*0 (0.8<p_T<5.0 GeV/c) and ρ_00 = 0.34 ± 0.02 (stat) ± 0.03 (syst) for the ϕ (0.4<p_T<5.0 GeV/c), and are constant with transverse momentum and collision
more » ... 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 ϕ in Au+Au collisions were also measured with respect to the particle's production plane. The ϕ result, ρ_00 = 0.41 ± 0.02 (stat) ± 0.04 (syst), is consistent with that in p+p collisions, ρ_00 = 0.39 ± 0.03 (stat) ± 0.06 (syst), also measured in this work. The measurements thus constrain the possible size of polarization phenomena in the production dynamics of vector mesons.
doi:10.1103/physrevc.77.061902 fatcat:rr2jvdads5ferbfwphfyyw6ete