Global quark polarization in non-central A+A collisions
Partons produced in the early stage of non-central heavy-ioncollisionscan develop a longitudinal fluid shear because of unequal localnumber densities of participant target and projectile nucleons. Undersuch fluid shear, local parton pairs with non-vanishing impact parameterhave finite local relative orbital angular momentum along the directionopposite to the reaction plane. Such finite relative orbitalangularmomentum among locally interacting quark pairs can lead to global quarkpolarization along the same direction due to spin-orbital coupling. Locallongitudinal fluid shear is estimated within both Landau fireball andBjorken scaling model of initial parton production. Quark polarizationthrough quark-quark scatterings with the exchange of a thermal gluon iscalculated beyond small-angle scattering approximation in a quark-gluonplasma. The polarization is shown to have a non-monotonic dependence onthe local relative orbital angular momentum dictated by the interplaybetween electric and magnetic interaction. It peaks at a value ofrelative orbital angular momentum which scales with the magnetic mass ofthe exchanged gluons. With the estimated small longitudinal fluid shearin semi-peripheral Au+Au collisions at the RHIC energy, the final quarkpolarization is found to be small left hbar P_q right hbar<0.04 inthe weak coupling limit. Possible behavior of the quark polarization inthe strong coupling limit and implications on the experimental detectionof such global quark polarization at RHIC and LHC are alsodiscussed.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE Director. Office of Science. NuclearPhysics
- DOE Contract Number:
- DE-AC02-05CH11231
- OSTI ID:
- 928885
- Report Number(s):
- LBNL-63515; R&D Project: NTCOST; BnR: KB0301020; TRN: US0803276
- Journal Information:
- Physical Review C, Vol. 0, Issue 0; Related Information: Journal Publication Date: 0
- Country of Publication:
- United States
- Language:
- English
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