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arXiv · 1111.5637

Energy and system-size dependence of two- and four-particle $v_2$ measurements in heavy-ion collisions at RHIC and their implications on flow fluctuations and nonflow

Abstract

We present STAR measurements of azimuthal anisotropy by means of the two- and four-particle cumulants $v_2$ ($v_2\{2\}$ and $v_2\{4\}$) for Au+Au and Cu+Cu collisions at center of mass energies $\sqrt{s_{_{\mathrm{NN}}}} = 62.4$ and 200 GeV. The difference between $v_2\{2\}^2$ and $v_2\{4\}^2$ is related to $v_{2}$ fluctuations ($\sigma_{v_2}$) and nonflow $(\delta_{2})$. We present an upper limit to $\sigma_{v_2}/v_{2}$. Following the assumption that eccentricity fluctuations $\sigma_{\epsilon}$ dominate $v_2$ fluctuations $\frac{\sigma_{v_2}}{v_2} \approx \frac{\sigma_{\epsilon}}{\epsilon}$ we deduce the nonflow implied for several models of eccentricity fluctuations that would be required for consistency with $v_2\{2\}$ and $v_2\{4\}$. We also present results on the ratio of $v_2$ to eccentricity.

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The STAR Collaboration, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, A. V. Alakhverdyants, I. Alekseev, J. Alford, B. D. Anderson, C. D. Anson, D. Arkhipkin, G. S. Averichev, J. Balewski, Z. Barnovska, D. R. Beavis, R. Bellwied, M. J. Betancourt, R. R. Betts, A. Bhasin, A. K. Bhati, H. Bichsel, J. Bielcik, J. Bielcikova, L. C. Bland, I. G. Bordyuzhin, W. Borowski, J. Bouchet, A. V. Brandin, S. G. Brovko, E. Bruna, S. Bueltmann, I. Bunzarov, T. P. Burton, X. Z. Cai, H. Caines, M. Calderon, D. Cebra, R. Cendejas, M. C. Cervantes, P. Chaloupka, S. Chattopadhyay, H. F. Chen, J. H. Chen, J. Y. Chen, L. Chen, J. Cheng, M. Cherney, A. Chikanian, W. Christie, P. Chung, M. J. M. Codrington, R. Corliss, J. G. Cramer, H. J. Crawford, X. Cui, A. Davila Leyva, L. C. De Silva, R. R. Debbe, T. G. Dedovich, J. Deng, R. Derradi de Souza, S. Dhamija, L. Didenko, F. Ding, P. Djawotho, X. Dong, J. L. Drachenberg, J. E. Draper, C. M. Du, L. E. Dunkelberger, J. C. Dunlop, L. G. Efimov, M. Elnimr, J. Engelage, G. Eppley, L. Eun, O. Evdokimov, R. Fatemi, J. Fedorisin, R. G. Fersch, P. Filip, E. Finch, Y. Fisyak, C. A. Gagliardi, D. R. Gangadharan, F. Geurts, P. Ghosh, S. Gliske, Y. N. Gorbunov, O. G. Grebenyuk, D. Grosnick, S. Gupta, W. Guryn, B. Haag, O. Hajkova, A. Hamed, L-X. Han, J. W. Harris, J. P. Hays-Wehle, S. Heppelmann, A. Hirsch. 2011-11-23. Energy and system-size dependence of two- and four-particle $v_2$ measurements in heavy-ion collisions at RHIC and their implications on flow fluctuations and nonflow. https://doi.org/10.1103/physrevc.86.014904

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