$J/\psi$ polarization in p+p collisions at $\sqrt{s}$ = 200 GeV in STAR

Abstract

We report on a polarization measurement of inclusive $J/\psi$ mesons in the di-electron decay channel at mid-rapidity at 2 $<p_T<$ 6 GeV/$c$ in $p+p$ collisions at $\sqrt{s}$ = 200 GeV. Data were taken with the STAR detector at RHIC. The $J/\psi$ polarization measurement should help to distinguish between different models of the $J/\psi$ production mechanism since they predict different $p_T$ dependences of the $J/\psi$ polarization. In this analysis, $J/\psi$ polarization is studied in the helicity frame. The polarization parameter ${\lambda }_{\theta }$ measured at RHIC becomes smaller towards high $p_T$, indicating more longitudinal $J/\psi$ polarization as $p_T$ increases. The result is compared with predictions of presently available models.

11 pages, 4 figures

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Cited by in corpus (7)

• $J/\psi$ polarization in high multiplicity $pp$ and $pA$ collisions: CGC+NRQCD approach
• Measurement of inclusive J/$\psi$ polarization in p+p collisions at $\sqrt{s}$ = 200 GeV by the STAR experiment
• J/$\psi$ and $\psi (2S)$ measurement in p+p collisions at $\sqrt{s}=$ 200 and 500 GeV with the STAR experiment
• Measurement of inclusive electrons from open heavy-flavor hadron decays in $p$+$p$ collisions at $\sqrt{s}=200$ GeV with the STAR detector
• $J/\psi$ and $\psi$(2S) polarization in proton-proton collisions at energies available at the CERN Large Hadron Collider using PYTHIA8
• Procedure for measuring particle's circular polarization variation with respect to the reaction plane in relativistic heavy-ion collisions
• The Hadronization Impact on $J/\psi$ Energy Correlators: A Pythia8 Study from Partonic to Hadronic Observables