MEASUREMENT OF GLOBAL SPIN ALIGNMENT OF VECTOR MESONS AT RHIC

We report on the measurements of spin alignment (rho(00)) for K*0, (K*0) over bar, K*(+), and K*- vector mesons in the RHIC isobar collisions (Zr+Zr and Ru+Ru) at root s(NN) = 200 GeV. We observe the first non-zero spin alignment for K*(+/-) in heavy-ion collisions. The K*(+/-) rho(00) is about 3.9 sigma larger than that of K*(0). The observed difference and the ordering between K*(+/-) and K*(0) are surprising and require further inputs from theory. When comparing the isobar and Au+Au collisions, no significant system size dependence in K*(0) rho(00) is observed within uncertainties.