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arXiv · 1311.1621

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

STAR Collaboration·L. Adamczyk·J. K. Adkins·G. Agakishiev·M. M. Aggarwal·Z. Ahammed·I. Alekseev·J. Alford·C. D. Anson·A. Aparin·D. Arkhipkin·E. C. Aschenauer·G. S. Averichev·J. Balewski·A. Banerjee·Z. Barnovska·D. R. Beavis·R. Bellwied·A. Bhasin·A. K. Bhati·P. Bhattarai·H. Bichsel·J. Bielcik·J. Bielcikova·L. C. Bland·I. G. Bordyuzhin·W. Borowski·J. Bouchet·A. V. Brandin·S. G. Brovko·S. Bültmann·I. Bunzarov·T. P. Burton·J. Butterworth·H. Caines·M. Calderón de la Barca Sánchez·D. Cebra·R. Cendejas·M. C. Cervantes·P. Chaloupka·Z. Chang·S. Chattopadhyay·H. F. Chen·J. H. Chen·L. Chen·J. Cheng·M. Cherney·A. Chikanian·W. Christie·J. Chwastowski·M. J. M. Codrington·R. Corliss·J. G. Cramer·H. J. Crawford·X. Cui·S. Das·A. Davila Leyva·L. C. De Silva·R. R. Debbe·T. G. Dedovich·J. Deng·A. A. Derevschikov·R. Derradi de Souza·S. Dhamija·B. di Ruzza·L. Didenko·C. Dilks·F. Ding·P. Djawotho·X. Dong·J. L. Drachenberg·J. E. Draper·C. M. Du·L. E. Dunkelberger·J. C. Dunlop·L. G. Efimov·J. Engelage·K. S. Engle·G. Eppley·L. Eun·O. Evdokimov·R. Fatemi·S. Fazio·J. Fedorisin·P. Filip·E. Finch·Y. Fisyak·C. E. Flores·C. A. Gagliardi·D. R. Gangadharan·D. Garand·F. Geurts·A. Gibson·M. Girard·S. Gliske·D. Grosnick·Y. Guo·A. Gupta·S. Gupta·W. Guryn
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Abstract

We report on a polarization measurement of inclusive $J/ψ$ 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 $J/ψ$ polarization measurement should help to distinguish between different models of the $J/ψ$ production mechanism since they predict different $p_{T}$ dependences of the $J/ψ$ polarization. In this analysis, $J/ψ$ polarization is studied in the helicity frame. The polarization parameter $λ_θ$ measured at RHIC becomes smaller towards high $p_{T}$, indicating more longitudinal $J/ψ$ polarization as $p_{T}$ increases. The result is compared with predictions of presently available models.

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STAR Collaboration, L. Adamczyk, J. K. Adkins, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, I. Alekseev, J. Alford, C. D. Anson, A. Aparin, D. Arkhipkin, E. C. Aschenauer, G. S. Averichev, J. Balewski, A. Banerjee, Z. Barnovska, D. R. Beavis, R. Bellwied, A. Bhasin, A. K. Bhati, P. Bhattarai, H. Bichsel, J. Bielcik, J. Bielcikova, L. C. Bland, I. G. Bordyuzhin, W. Borowski, J. Bouchet, A. V. Brandin, S. G. Brovko, S. Bültmann, I. Bunzarov, T. P. Burton, J. Butterworth, H. Caines, M. Calderón de la Barca Sánchez, D. Cebra, R. Cendejas, M. C. Cervantes, P. Chaloupka, Z. Chang, S. Chattopadhyay, H. F. Chen, J. H. Chen, L. Chen, J. Cheng, M. Cherney, A. Chikanian, W. Christie, J. Chwastowski, M. J. M. Codrington, R. Corliss, J. G. Cramer, H. J. Crawford, X. Cui, S. Das, A. Davila Leyva, L. C. De Silva, R. R. Debbe, T. G. Dedovich, J. Deng, A. A. Derevschikov, R. Derradi de Souza, S. Dhamija, B. di Ruzza, L. Didenko, C. Dilks, F. Ding, P. Djawotho, X. Dong, J. L. Drachenberg, J. E. Draper, C. M. Du, L. E. Dunkelberger, J. C. Dunlop, L. G. Efimov, J. Engelage, K. S. Engle, G. Eppley, L. Eun, O. Evdokimov, R. Fatemi, S. Fazio, J. Fedorisin, P. Filip, E. Finch, Y. Fisyak, C. E. Flores, C. A. Gagliardi, D. R. Gangadharan, D. Garand, F. Geurts, A. Gibson, M. Girard, S. Gliske, D. Grosnick, Y. Guo, A. Gupta, S. Gupta, W. Guryn. 2014-11-18. $J/ψ$ polarization in p+p collisions at $\sqrt{s}$ = 200 GeV in STAR. https://doi.org/10.1016/j.physletb.2014.10.049

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