J/ψ polarization in p+p collisions at s=200 GeV in STAR
We report on a polarization measurement of inclusive J/ψ mesons 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.
Adamczyk, L; Adkins, JK; Agakishiev, G; Aggarwal, MM; Ahammed, Z; Alekseev, I; Alford, J; Anson, CD; Aparin, A; Arkhipkin, D; Aschenauer, EC; Averichev, GS; Balewski, J; Banerjee, A; Barnovska, Z; Beavis, DR; Bellwied, R; Bhasin, A; Bhati, AK; Bhattarai, P; Bichsel, H; Bielcik, J; Bielcikova, J; Bland, LC; Bordyuzhin, IG; Borowski, W; Bouchet, J; Brandin, AV; Brovko, SG; Bültmann, S; Bunzarov, I; Burton, TP; Butterworth, J; Caines, H; Calderón De La Barca Sánchez, M; Cebra, D; Cendejas, R; Cervantes, MC; Chaloupka, P; Chang, Z; Chattopadhyay, S; Chen, HF; Chen, JH; Chen, L; Cheng, J; Cherney, M; Chikanian, A; Christie, W; Chwastowski, J; Codrington, MJM; Corliss, R; Cramer, JG; Crawford, HJ; Cui, X; Das, S; Davila Leyva, A; De Silva, LC; Debbe, RR; Dedovich, TG; Deng, J; Derevschikov, AA; Derradi De Souza, R; Dhamija, S; Di Ruzza, B; Didenko, L; Dilks, C; Ding, F; Djawotho, P; Dong, X; Drachenberg, JL; Draper, JE; Du, CM; Dunkelberger, LE; Dunlop, JC; Efimov, LG; Engelage, J; Engle, KS; Eppley, G; Eun, L; Evdokimov, O; Fatemi, R; Fazio, S; Fedorisin, J; Filip, P; Finch, E; Fisyak, Y; Flores, CE; Gagliardi, CA; Gangadharan, DR; Garand, D; Geurts, F; Gibson, A; Girard, M; Gliske, S; Grosnick, D; Guo, Y; Gupta, A; Gupta, S; Guryn, W; Haag, B
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