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arXiv · 2007.04732

Measurement of inclusive J/$\psi$ polarization in p+p collisions at $\sqrt{s}$ = 200 GeV by the STAR experiment

STAR Collaboration·J. Adam·L. Adamczyk·J. R. Adams·J. K. Adkins·G. Agakishiev·M. M. Aggarwal·Z. Ahammed·I. Alekseev·D. M. Anderson·A. Aparin·E. C. Aschenauer·M. U. Ashraf·F. G. Atetalla·A. Attri·G. S. Averichev·V. Bairathi·K. Barish·A. Behera·R. Bellwied·A. Bhasin·J. Bielcik·J. Bielcikova·L. C. Bland·I. G. Bordyuzhin·J. D. Brandenburg·A. V. Brandin·J. Butterworth·H. Caines·M. Calderón de la Barca Sánchez·D. Cebra·I. Chakaberia·P. Chaloupka·B. K. Chan·F-H. Chang·Z. Chang·N. Chankova-Bunzarova·A. Chatterjee·D. Chen·J. H. Chen·X. Chen·Z. Chen·J. Cheng·M. Cherney·M. Chevalier·S. Choudhury·W. Christie·X. Chu·H. J. Crawford·M. Csanád·M. Daugherity·T. G. Dedovich·I. M. Deppner·A. A. Derevschikov·L. Didenko·X. Dong·J. L. Drachenberg·J. C. Dunlop·T. Edmonds·N. Elsey·J. Engelage·G. Eppley·R. Esha·S. Esumi·O. Evdokimov·A. Ewigleben·O. Eyser·R. Fatemi·S. Fazio·P. Federic·J. Fedorisin·C. J. Feng·Y. Feng·P. Filip·E. Finch·Y. Fisyak·A. Francisco·L. Fulek·C. A. Gagliardi·T. Galatyuk·F. Geurts·A. Gibson·K. Gopal·D. Grosnick·W. Guryn·A. I. Hamad·A. Hamed·S. Harabasz·J. W. Harris·S. He·W. He·X. H. He·S. Heppelmann·N. Herrmann·E. Hoffman·L. Holub·Y. Hong·S. Horvat·Y. Hu·H. Z. Huang
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Abstract

We report on new measurements of inclusive J/$\psi$ polarization at mid-rapidity in p+p collisions at $\sqrt{s}$ = 200 GeV by the STAR experiment at RHIC. The polarization parameters, $\lambda_\theta$, $\lambda_\phi$, and $\lambda_{\theta\phi}$, are measured as a function of transverse momentum ($p_T$) in both the Helicity and Collins-Soper (CS) reference frames within $p_T< 10$ GeV/$C$. Except for $\lambda_\theta$ in the CS frame at the highest measured $p_T$, all three polarization parameters are consistent with 0 in both reference frames without any strong $p_T$ dependence. Several model calculations are compared with data, and the one using the Color Glass Condensate effective field theory coupled with non-relativistic QCD gives the best overall description of the experimental results, even though other models cannot be ruled out due to experimental uncertainties.

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STAR Collaboration, J. Adam, L. Adamczyk, J. R. Adams, J. K. Adkins, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, I. Alekseev, D. M. Anderson, A. Aparin, E. C. Aschenauer, M. U. Ashraf, F. G. Atetalla, A. Attri, G. S. Averichev, V. Bairathi, K. Barish, A. Behera, R. Bellwied, A. Bhasin, J. Bielcik, J. Bielcikova, L. C. Bland, I. G. Bordyuzhin, J. D. Brandenburg, A. V. Brandin, J. Butterworth, H. Caines, M. Calderón de la Barca Sánchez, D. Cebra, I. Chakaberia, P. Chaloupka, B. K. Chan, F-H. Chang, Z. Chang, N. Chankova-Bunzarova, A. Chatterjee, D. Chen, J. H. Chen, X. Chen, Z. Chen, J. Cheng, M. Cherney, M. Chevalier, S. Choudhury, W. Christie, X. Chu, H. J. Crawford, M. Csanád, M. Daugherity, T. G. Dedovich, I. M. Deppner, A. A. Derevschikov, L. Didenko, X. Dong, J. L. Drachenberg, J. C. Dunlop, T. Edmonds, N. Elsey, J. Engelage, G. Eppley, R. Esha, S. Esumi, O. Evdokimov, A. Ewigleben, O. Eyser, R. Fatemi, S. Fazio, P. Federic, J. Fedorisin, C. J. Feng, Y. Feng, P. Filip, E. Finch, Y. Fisyak, A. Francisco, L. Fulek, C. A. Gagliardi, T. Galatyuk, F. Geurts, A. Gibson, K. Gopal, D. Grosnick, W. Guryn, A. I. Hamad, A. Hamed, S. Harabasz, J. W. Harris, S. He, W. He, X. H. He, S. Heppelmann, N. Herrmann, E. Hoffman, L. Holub, Y. Hong, S. Horvat, Y. Hu, H. Z. Huang. 2020-07-09. Measurement of inclusive J/$\psi$ polarization in p+p collisions at $\sqrt{s}$ = 200 GeV by the STAR experiment. https://doi.org/10.1103/physrevd.102.092009

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