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Spin alignment of K*0(892) and (1020) mesons in Au+Au and p+p collisions at \sqrt{s_{\rm NN}} = 200 GeV.

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Bibliographic Details
Title: Spin alignment of K*0(892) and (1020) mesons in Au+Au and p+p collisions at \sqrt{s_{\rm NN}} = 200 GeV.
Authors: J H Chen, for the, STAR Collaboration
Source: Journal of Physics G: Nuclear & Particle Physics. Apr2008, Vol. 35 Issue 4, p44068-44068. 1p.
Subjects: Collisions (Nuclear physics), Mesons, Polarization (Nuclear physics), Nuclear physics
Abstract: We present the first spin alignment measurements for the vector mesons K*0(892) and ph(1020) at mid-rapidity in Au+Au and p+p collisions at \sqrt{s_{\rm NN}} = 200 GeV. Vector mesons appear to be produced without a strong spin alignment constraining possible spin transfer processes from a large orbital angular momentum of the colliding system as expected in theoretical calculations. The diagonal spin density matrix elements are measured to be r00 = 0.32 ± 0.04 (stat) ± 0.09 (syst) for the K*0 (0.8 < pT < 5.0 GeV/c) and r00 = 0.34 ± 0.02 (stat) ± 0.03 (syst) for the ph (0.4 < pT < 5.0 GeV/c), with respect to the reaction plane in midcentral Au+Au collisions, and are found to be independent of collision centrality and transverse momentum. r00 with respect to the production plane is measured to be less than 2s deviation above 1/3 in both Au+Au and p+p collisions indicating the absence of polarization phenomena in the production dynamics for vector mesons in the measured kinematic region. [ABSTRACT FROM AUTHOR]
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Abstract:We present the first spin alignment measurements for the vector mesons K*0(892) and ph(1020) at mid-rapidity in Au+Au and p+p collisions at \sqrt{s_{\rm NN}} = 200 GeV. Vector mesons appear to be produced without a strong spin alignment constraining possible spin transfer processes from a large orbital angular momentum of the colliding system as expected in theoretical calculations. The diagonal spin density matrix elements are measured to be r00 = 0.32 ± 0.04 (stat) ± 0.09 (syst) for the K*0 (0.8 < pT < 5.0 GeV/c) and r00 = 0.34 ± 0.02 (stat) ± 0.03 (syst) for the ph (0.4 < pT < 5.0 GeV/c), with respect to the reaction plane in midcentral Au+Au collisions, and are found to be independent of collision centrality and transverse momentum. r00 with respect to the production plane is measured to be less than 2s deviation above 1/3 in both Au+Au and p+p collisions indicating the absence of polarization phenomena in the production dynamics for vector mesons in the measured kinematic region. [ABSTRACT FROM AUTHOR]
ISSN:09543899