[J over ψ] polarization in p+p collisions at √s = 200 TeV in STAR
Author(s)Walker, M.; van Nieuwenhuizen, Gerrit Jan; Stevens, Justin; Balewski, Jan T.; Corliss, Ross; Hays-Wehle, James Prewitt; Leight, William Axel; ... Show more Show less
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We report on a polarization measurement of inclusive [J over ψ] mesons in the di-electron decay channel at mid-rapidity at 2<p[subscript T]<6 GeV/c in p+p collisions at √s = 200 GeV. Data were taken with the STAR detector at RHIC. The [J over ψ] polarization measurement should help to distinguish between different models of the [J over ψ] production mechanism since they predict different p[subscript T] dependences of the [J over ψ] polarization. In this analysis, [J over ψ] polarization is studied in the helicity frame. The polarization parameter λ[subscript θ] measured at RHIC becomes smaller towards high p[subscript T], indicating more longitudinal [J over ψ] polarization as p[subscript T] increases. The result is compared with predictions of presently available models.
DepartmentMassachusetts Institute of Technology. Laboratory for Nuclear Science
Physics Letters B
“[J over ψ] polarization in p+p collisions at √s = 200 TeV in STAR.” Physics Letters B 739 (December 2014): 180–188.
Final published version