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 root 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 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. (C) 2014 The Authors. Published by Elsevier B.V.
J/psi polarization in p plus p collisions at root s=200 GeV in STAR
di Ruzza B;
2014-01-01
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 root 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 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. (C) 2014 The Authors. Published by Elsevier B.V.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
