engleski

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

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

J/Psi; polarization; STAR

STAR Collaboration