학술논문
Disentangling centrality bias and final-state effects in the production of high-$p_T$ $\pi^0$ using direct $\gamma$ in $d$$+$Au collisions at $\sqrt{s_{_{NN}}}=200$ GeV
Document Type
Working Paper
Author
Abdulameer, N. J.; Acharya, U.; Aidala, C.; Akiba, Y.; Alfred, M.; Aoki, K.; Apadula, N.; Ayuso, C.; Babintsev, V.; Barish, K. N.; Bathe, S.; Bazilevsky, A.; Belmont, R.; Berdnikov, A.; Berdnikov, Y.; Bichon, L.; Blankenship, B.; Blau, D. S.; Boer, M.; Bok, J. S.; Borisov, V.; Brooks, M. L.; Bryslawskyj, J.; Bumazhnov, V.; Butler, C.; Campbell, S.; Roman, V. Canoa; Chiu, M.; Connors, M.; Corliss, R.; Morales, Y. Corrales; Csanád, M.; Csörgő, T.; Liu, L. D.; Danley, T. W.; Daugherity, M. S.; David, G.; Dean, C. T.; DeBlasio, K.; Dehmelt, K.; Denisov, A.; Deshpande, A.; Desmond, E. J.; Doomra, V.; Do, J. H.; Drees, A.; Drees, K. A.; Dumancic, M.; Durham, J. M.; Durum, A.; Elder, T.; Enokizono, A.; Esha, R.; Fadem, B.; Fan, W.; Feege, N.; Finger, Jr., M.; Finger, M.; Firak, D.; Fitzgerald, D.; Fokin, S. L.; Frantz, J. E.; Franz, A.; Frawley, A. D.; Fukuda, Y.; Gal, C.; Garg, P.; Ge, H.; Giles, M.; Goto, Y.; Grau, N.; Greene, S. V.; Gunji, T.; Hachiya, T.; Haggerty, J. S.; Hahn, K. I.; Han, S. Y.; Harvey, M.; Hasegawa, S.; Haseler, T. O. S.; Hemmick, T. K.; He, X.; Hill, K.; Hodges, A.; Homma, K.; Hong, B.; Hoshino, T.; Hotvedt, N.; Huang, J.; Imrek, J.; Inaba, M.; Isenhower, D.; Ito, Y.; Ivanishchev, D.; Jacak, B. V.; Ji, Z.; Johnson, B. M.; Jorjadze, V.; Jouan, D.; Jumper, D. S.; Kang, J. H.; Kapukchyan, D.; Karthas, S.; Kazantsev, A. V.; Khachatryan, V.; Khanzadeev, A.; Khatiwada, A.; Kim, C.; Kim, D. J.; Kim, E. -J.; Kim, M.; Kim, M. H.; Kim, T.; Kincses, D.; Kingan, A.; Kistenev, E.; Koblesky, T.; Kotov, D.; Kovacs, L.; Kudo, S.; Kurgyis, B.; Kurita, K.; Lajoie, J. G.; Lallow, E. O.; Larionova, D.; Lebedev, A.; Lee, S. H.; Leitch, M. J.; Leung, Y. H.; Lewis, N. A.; Lim, S. H.; Liu, M. X.; Li, X.; Loggins, V. -R.; Loomis, D. A.; Lynch, D.; Lökös, S.; Majoros, T.; Makek, M.; Malaev, M.; Manko, V. I.; Mannel, E.; Masuda, H.; McCumber, M.; McGlinchey, D.; Mignerey, A. C.; Mihalik, D. E.; Milov, A.; Mishra, D. K.; Mitchell, J. T.; Mitrankova, M.; Mitrankov, Iu.; Mitsuka, G.; Mondal, M. M.; Moon, T.; Morrison, D. P.; Morrow, S. I.; Muhammad, A.; Mulilo, B.; Murakami, T.; Murata, J.; Nagai, K.; Nagashima, K.; Nagashima, T.; Nagle, J. L.; Nagy, M. I.; Nakagawa, I.; Nakagomi, H.; Nakano, K.; Nattrass, C.; Nelson, S.; Nouicer, R.; Novitzky, N.; Novotny, R.; Novák, T.; Nukazuka, G.; Nyanin, A. S.; O'Brien, E.; Ogilvie, C. A.; Oh, J.; Koop, J. D. Orjuela; Orosz, M.; Osborn, J. D.; Oskarsson, A.; Ozawa, K.; Pantuev, V.; Papavassiliou, V.; Park, J. S.; Park, S.; Patel, M.; Pate, S. F.; Peng, W.; Perepelitsa, D. V.; Perera, G. D. N.; PerezLara, C. E.; Petti, R.; Phipps, M.; Pinkenburg, C.; Potekhin, M.; Pun, A.; Purschke, M. L.; Radzevich, P. V.; Ramasubramanian, N.; Read, K. F.; Riabov, V.; Riabov, Y.; Richford, D.; Rinn, T.; Rosati, M.; Rowan, Z.; Runchey, J.; Sakaguchi, T.; Sako, H.; Samsonov, V.; Sarsour, M.; Sato, K.; Sato, S.; Schaefer, B.; Schmoll, B. K.; Seidl, R.; Sen, A.; Seto, R.; Sexton, A.; Sharma, D.; Shein, I.; Shibata, M.; Shibata, T. -A.; Shigaki, K.; Shimomura, M.; Shi, Z.; Silva, C. L.; Silvermyr, D.; Slunečka, M.; Smith, K. L.; Sorensen, S. P.; Sourikova, I. V.; Stankus, P. W.; Stoll, S. P.; Sugitate, T.; Sukhanov, A.; Sun, Z.; Syed, S.; Takahama, R.; Takeda, A.; Tanida, K.; Tannenbaum, M. J.; Tarafdar, S.; Taranenko, A.; Tarnai, G.; Tieulent, R.; Timilsina, A.; Todoroki, T.; Tomášek, M.; Towell, C. L.; Towell, R. S.; Tserruya, I.; Ueda, Y.; Ujvari, B.; van Hecke, H. W.; Vazquez-Carson, S.; Velkovska, J.; Virius, M.; Vrba, V.; Wang, X. R.; Wang, Z.; Watanabe, Y.; Wong, C. P.; Xu, C.; Xu, Q.; Yamaguchi, Y. L.; Yanovich, A.; Yin, P.; Yoon, I.; Yoo, J. H.; Yushmanov, I. E.; Yu, H.; Zajc, W. A.; Zou, L.
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Abstract
PHENIX presents a simultaneous measurement of the production of direct $\gamma$ and $\pi^0$ in $d$$+$Au collisions at $\sqrt{s_{_{NN}}}=200$ GeV over a $p_T$ range of 7.5 to 18 GeV/$c$ for different event samples selected by event activity, i.e. charged-particle multiplicity detected at forward rapidity. Direct-photon yields are used to empirically estimate the contribution of hard-scattering processes in the different event samples. Using this estimate, the average nuclear-modification factor $R_{d\rm Au,EXP}^{\gamma^{\rm dir}}$ is $0.925{\pm}0.023({\rm stat}){\pm}0.15^{\rm (scale)}$, consistent with unity for minimum-bias (MB) $d$$+$Au events. For event classes with moderate event activity, $R_{d\rm Au,EXP}^{\gamma^{\rm dir}}$ is consistent with the MB value within 5\% uncertainty. These results confirm that the previously observed enhancement of high-$p_T$ $\pi^0$ production found in small-system collisions with low event activity is a result of a bias in interpreting event activity within the Glauber framework. In contrast, for the top 5\% of events with the highest event activity, $R_{d\rm Au,EXP}^{\gamma^{\rm dir}}$ is suppressed by 20\% relative to the MB value with a significance of $4.5\sigma$, which may be due to final-state effects.
Comment: 279 authors from 69 institutions, 8 pages, 3 figures, v1 is version submitted to Physical Review Letters. HEPdata tables for the points plotted in figures for this and previous PHENIX publications are (or will be) publicly available at http://www.phenix.bnl.gov/papers.html
Comment: 279 authors from 69 institutions, 8 pages, 3 figures, v1 is version submitted to Physical Review Letters. HEPdata tables for the points plotted in figures for this and previous PHENIX publications are (or will be) publicly available at http://www.phenix.bnl.gov/papers.html