[J over ψ] polarization in p+p collisions at √s = 200 TeV in STAR

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 distingu...

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Bibliographic Details
Main Authors: Walker, M., van Nieuwenhuizen, Gerrit Jan, Stevens, Justin, Balewski, Jan T., Corliss, Ross, Hays-Wehle, James Prewitt, Leight, William Axel
Other Authors: Massachusetts Institute of Technology. Laboratory for Nuclear Science
Format: Article
Language:en_US
Published: Elsevier 2015
Online Access:http://hdl.handle.net/1721.1/94636
https://orcid.org/0000-0002-5515-4563
https://orcid.org/0000-0002-0816-200X
Description
Summary: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.

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