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arXiv · 1208.2254

Neutral pion production with respect to centrality and reaction plane in Au+Au collisions at sqrt(s_NN)=200 GeV

A. Adare·S. Afanasiev·C. Aidala·N. N. Ajitanand·Y. Akiba·H. Al-Bataineh·J. Alexander·K. Aoki·Y. Aramaki·E. T. Atomssa·R. Averbeck·T. C. Awes·B. Azmoun·V. Babintsev·M. Bai·G. Baksay·L. Baksay·K. N. Barish·B. Bassalleck·A. T. Basye·S. Bathe·V. Baublis·C. Baumann·A. Bazilevsky·S. Belikov·R. Belmont·R. Bennett·A. Berdnikov·Y. Berdnikov·A. A. Bickley·J. S. Bok·K. Boyle·M. L. Brooks·H. Buesching·V. Bumazhnov·G. Bunce·S. Butsyk·C. M. Camacho·S. Campbell·C. -H. Chen·C. Y. Chi·M. Chiu·I. J. Choi·R. K. Choudhury·P. Christiansen·T. Chujo·P. Chung·O. Chvala·V. Cianciolo·Z. Citron·B. A. Cole·M. Connors·P. Constantin·M. Csanád·T. Csörgő·T. Dahms·S. Dairaku·I. Danchev·K. Das·A. Datta·G. David·A. Denisov·A. Deshpande·E. J. Desmond·O. Dietzsch·A. Dion·M. Donadelli·O. Drapier·A. Drees·K. A. Drees·J. M. Durham·A. Durum·D. Dutta·S. Edwards·Y. V. Efremenko·F. Ellinghaus·T. Engelmore·A. Enokizono·H. En'yo·S. Esumi·B. Fadem·D. E. Fields·M. Finger·M. Finger Jr·F. Fleuret·S. L. Fokin·Z. Fraenkel·J. E. Frantz·A. Franz·A. D. Frawley·K. Fujiwara·Y. Fukao·T. Fusayasu·I. Garishvili·A. Glenn·H. Gong·M. Gonin·Y. Goto·R. Granier de Cassagnac·N. Grau
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Abstract

The PHENIX experiment has measured the production of neutral pions in Au+Au collisions at sqrt(s_NN)=200 GeV. The new data offer a fourfold increase in recorded luminosity, providing higher precision and a larger reach in transverse momentum, p_T, to 20 GeV/c. The production ratio of eta/pi^0 is 0.46+/-0.01(stat)+/-0.05(syst), constant with p_T and collision centrality. The observed ratio is consistent with earlier measurements, as well as with the p+p and d+Au values. The production of pi^0 is suppressed by a factor of 5, as in earlier findings. However, with the improved statistical precision a small but significant rise of the nuclear modification factor, R_AA, vs p_T, with a slope of 0.0106+/-^(0.0034)_(0.0029)[GeV/c]^-1, is discernible in central collisions. A phenomenological extraction of the average fractional parton energy loss shows a decrease with increasing p_T. To study the path length dependence of suppression, the pi^0 yield was measured at different angles with respect to the event plane; a strong azimuthal dependence of the pi^0 R_AA is observed. The data are compared to theoretical models of parton energy loss as a function of the path length, L, in the medium. Models based on pQCD are insufficient to describe the data, while a hybrid model utilizing pQCD for the hard interactions and AdS/CFT for the soft interactions is consistent with the data.

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A. Adare, S. Afanasiev, C. Aidala, N. N. Ajitanand, Y. Akiba, H. Al-Bataineh, J. Alexander, K. Aoki, Y. Aramaki, E. T. Atomssa, R. Averbeck, T. C. Awes, B. Azmoun, V. Babintsev, M. Bai, G. Baksay, L. Baksay, K. N. Barish, B. Bassalleck, A. T. Basye, S. Bathe, V. Baublis, C. Baumann, A. Bazilevsky, S. Belikov, R. Belmont, R. Bennett, A. Berdnikov, Y. Berdnikov, A. A. Bickley, J. S. Bok, K. Boyle, M. L. Brooks, H. Buesching, V. Bumazhnov, G. Bunce, S. Butsyk, C. M. Camacho, S. Campbell, C. -H. Chen, C. Y. Chi, M. Chiu, I. J. Choi, R. K. Choudhury, P. Christiansen, T. Chujo, P. Chung, O. Chvala, V. Cianciolo, Z. Citron, B. A. Cole, M. Connors, P. Constantin, M. Csanád, T. Csörgő, T. Dahms, S. Dairaku, I. Danchev, K. Das, A. Datta, G. David, A. Denisov, A. Deshpande, E. J. Desmond, O. Dietzsch, A. Dion, M. Donadelli, O. Drapier, A. Drees, K. A. Drees, J. M. Durham, A. Durum, D. Dutta, S. Edwards, Y. V. Efremenko, F. Ellinghaus, T. Engelmore, A. Enokizono, H. En'yo, S. Esumi, B. Fadem, D. E. Fields, M. Finger, M. Finger Jr, F. Fleuret, S. L. Fokin, Z. Fraenkel, J. E. Frantz, A. Franz, A. D. Frawley, K. Fujiwara, Y. Fukao, T. Fusayasu, I. Garishvili, A. Glenn, H. Gong, M. Gonin, Y. Goto, R. Granier de Cassagnac, N. Grau. 2013-01-23. Neutral pion production with respect to centrality and reaction plane in Au+Au collisions at sqrt(s_NN)=200 GeV. https://doi.org/10.1103/physrevc.87.034911

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