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Phys. Rev. C 77, 061902(R) (2008) [7 pages]

Spin alignment measurements of the K*0(892) and ϕ(1020) vector mesons in heavy ion collisions at sNN=200 GeV

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B. I. Abelev et al. STAR Collaboration
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Received 11 January 2008; published 12 June 2008

We present the first spin alignment measurements for the K*0(892) and ϕ(1020) vector mesons produced at midrapidity with transverse momenta up to 5 GeV/c at sNN=200 GeV at RHIC. The diagonal spin-density matrix elements with respect to the reaction plane in Au+Au collisions are ρ00=0.32±0.04 (stat) ± 0.09 (syst) for the K*0 (0.8<pT<5.0 GeV/c) and ρ00=0.34±0.02 (stat) ± 0.03 (syst) for the ϕ (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 ϕ in Au+Au collisions were also measured with respect to the particle's production plane. The ϕ result, ρ00=0.41±0.02 (stat) ± 0.04 (syst), is consistent with that in p+p collisions, ρ00=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.

© 2008 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevC.77.061902
DOI:
10.1103/PhysRevC.77.061902
PACS:
24.70.+s, 25.75.Nq