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Evolution of pi(0) Suppression in Au plus Au Collisions from root s(NN)=39 to 200 GeV

Adare, A.; Afanasiev, S.; Aidala, C.; Ajitanand, N. N.; Akiba, Y.; Akimoto, R.; Al-Ta'ani, H.; Alexander, J.; Angerami, A. and Aoki, K., et al. (2012) In Physical Review Letters 109(15).
Abstract
Neutral-pion pi(0) spectra were measured at midrapidity (vertical bar y vertical bar < 0.35) in Au + Au collisions at root s(NN) = 39 and 62.4 GeV and compared with earlier measurements at 200 GeV in a transverse-momentum range of 1 < p(T) < 10 GeV/c. The high-p(T) tail is well described by a power law in all cases, and the powers decrease significantly with decreasing center-of-mass energy. The change of powers is very similar to that observed in the corresponding spectra for p + p collisions. The nuclear modification factors (RAA) show significant suppression, with a distinct energy, centrality, and p(T) dependence. Above p(T) = 7 GeV/c, R-AA is similar for root sNN = 62.4 and 200 GeV at all centralities.... (More)
Neutral-pion pi(0) spectra were measured at midrapidity (vertical bar y vertical bar < 0.35) in Au + Au collisions at root s(NN) = 39 and 62.4 GeV and compared with earlier measurements at 200 GeV in a transverse-momentum range of 1 < p(T) < 10 GeV/c. The high-p(T) tail is well described by a power law in all cases, and the powers decrease significantly with decreasing center-of-mass energy. The change of powers is very similar to that observed in the corresponding spectra for p + p collisions. The nuclear modification factors (RAA) show significant suppression, with a distinct energy, centrality, and p(T) dependence. Above p(T) = 7 GeV/c, R-AA is similar for root sNN = 62.4 and 200 GeV at all centralities. Perturbative-quantum-chromodynamics calculations that describe R-AA well at 200 GeV fail to describe the 39 GeV data, raising the possibility that, for the same p(T) region, the relative importance of initial-state effects and soft processes increases at lower energies. The p(T) range where pi(0) spectra in central Au + Au collisions have the same power as in p + p collisions is approximate to 5 and 7 GeV/c for root sNN = 200 and 62.4 GeV, respectively. For the root sNN = 39 GeV data, it is not clear whether such a region is reached, and the x(T) dependence of the x(T)-scaling power-law exponent is very different from that observed in the root sNN = 62 and 200 GeV data, providing further evidence that initial-state effects and soft processes mask the in-medium suppression of hardscattered partons to higher p(T) as the collision energy decreases. (Less)
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Physical Review Letters
volume
109
issue
15
publisher
American Physical Society
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  • scopus:84867364497
ISSN
1079-7114
DOI
10.1103/PhysRevLett.109.152301
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English
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547f5778-77c8-4153-b07d-4aea03717886 (old id 3174200)
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2012-12-12 09:19:41
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@article{547f5778-77c8-4153-b07d-4aea03717886,
  abstract     = {Neutral-pion pi(0) spectra were measured at midrapidity (vertical bar y vertical bar &lt; 0.35) in Au + Au collisions at root s(NN) = 39 and 62.4 GeV and compared with earlier measurements at 200 GeV in a transverse-momentum range of 1 &lt; p(T) &lt; 10 GeV/c. The high-p(T) tail is well described by a power law in all cases, and the powers decrease significantly with decreasing center-of-mass energy. The change of powers is very similar to that observed in the corresponding spectra for p + p collisions. The nuclear modification factors (RAA) show significant suppression, with a distinct energy, centrality, and p(T) dependence. Above p(T) = 7 GeV/c, R-AA is similar for root sNN = 62.4 and 200 GeV at all centralities. Perturbative-quantum-chromodynamics calculations that describe R-AA well at 200 GeV fail to describe the 39 GeV data, raising the possibility that, for the same p(T) region, the relative importance of initial-state effects and soft processes increases at lower energies. The p(T) range where pi(0) spectra in central Au + Au collisions have the same power as in p + p collisions is approximate to 5 and 7 GeV/c for root sNN = 200 and 62.4 GeV, respectively. For the root sNN = 39 GeV data, it is not clear whether such a region is reached, and the x(T) dependence of the x(T)-scaling power-law exponent is very different from that observed in the root sNN = 62 and 200 GeV data, providing further evidence that initial-state effects and soft processes mask the in-medium suppression of hardscattered partons to higher p(T) as the collision energy decreases.},
  articleno    = {152301},
  author       = {Adare, A. and Afanasiev, S. and Aidala, C. and Ajitanand, N. N. and Akiba, Y. and Akimoto, R. and Al-Ta'ani, H. and Alexander, J. and Angerami, A. and Aoki, K. and Apadula, N. and Aramaki, Y. and Asano, H. and Aschenauer, E. C. and Atomssa, E. T. and Awes, T. C. and Azmoun, B. and Babintsev, V. and Bai, M. and Bannier, B. and Barish, K. N. and Bassalleck, B. and Bathe, S. and Baublis, V. and Baumgart, S. and Bazilevsky, A. and Belmont, R. and Berdnikov, A. and Berdnikov, Y. and Bing, X. and Blau, D. S. and Boyle, K. and Brooks, M. L. and Buesching, H. and Bumazhnov, V. and Butsyk, S. and Campbell, S. and Castera, P. and Chen, C. -H. and Chi, C. Y. and Chiu, M. and Choi, I. J. and Choi, J. B. and Choi, S. and Choudhury, R. K. and Christiansen, Peter and Chujo, T. and Chvala, O. and Cianciolo, V. and Citron, Z. and Cole, B. A. and Connors, M. and Csanad, M. and Csoergo, T. and Dairaku, S. and Datta, A. and Daugherity, M. 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S. and Homma, K. and Hong, B. and Horaguchi, T. and Hori, Y. and Huang, S. and Ichihara, T. and Iinuma, H. and Ikeda, Y. and Imrek, J. and Inaba, M. and Iordanova, A. and Isenhower, D. and Issah, M. and Isupov, A. and Ivanischev, D. and Jacak, B. V. and Javani, M. and Jia, J. and Jiang, X. and Johnson, B. M. and Joo, K. S. and Jouan, D. and Kamin, J. and Kaneti, S. and Kang, B. H. and Kang, J. H. and Kang, J. S. and Kapustinsky, J. and Karatsu, K. and Kasai, M. and Kawall, D. and Kazantsev, A. V. and Kempel, T. and Khanzadeev, A. and Kijima, K. M. and Kim, B. I. and Kim, C. and Kim, D. J. and Kim, E. -J. and Kim, H. J. and Kim, K. -B. and Kim, Y. -J. and Kim, Y. K. and Kinney, E. and Kiss, A. and Kistenev, E. and Klatsky, J. and Kleinjan, D. and Kline, P. and Komatsu, Y. and Komkov, B. and Koster, J. and Kotchetkov, D. and Kotov, D. and Kral, A. and Krizek, F. and Kunde, G. J. and Kurita, K. and Kurosawa, M. and Kwon, Y. and Kyle, G. S. and Lacey, R. and Lai, Y. S. and Lajoie, J. G. and Lebedev, A. and Lee, B. and Lee, D. M. and Lee, J. and Lee, K. B. and Lee, K. S. and Lee, S. H. and Lee, S. R. and Leitch, M. J. and Leite, M. A. L. and Leitgab, M. and Lewis, B. and Lim, S. H. and Levy, L. A. Linden and Litvinenko, A. and Liu, M. X. and Love, B. and Maguire, C. F. and Makdisi, Y. I. and Makek, M. and Malakhov, A. and Manion, A. and Manko, V. I. and Mannel, E. and Masumoto, S. and McCumber, M. and McGaughey, P. L. and McGlinchey, D. and McKinney, C. and Mendoza, M. and Meredith, B. and Miake, Y. and Mibe, T. and Mignerey, A. C. and Milov, A. and Mishra, D. K. and Mitchell, J. T. and Miyachi, Y. and Miyasaka, S. and Mohanty, A. K. and Moon, H. J. and Morrison, D. P. and Motschwiller, S. and Moukhanova, T. V. and Murakami, T. and Murata, J. and Nagae, T. and Nagamiya, S. and Nagle, J. L. and Nagy, M. I. and Nakagawa, I. and Nakamiya, Y. and Nakamura, K. R. and Nakamura, T. and Nakano, K. and Nattrass, C. and Nederlof, A. and Nihashi, M. and Nouicer, R. and Novitzky, N. and Nyanin, A. S. and O'Brien, E. and Ogilvie, C. A. and Okada, K. and Oskarsson, Anders and Ouchida, M. and Ozawa, K. and Pak, R. and Pantuev, V. and Papavassiliou, V. and Park, B. H. and Park, I. H. and Park, S. K. and Pate, S. F. and Patel, L. and Pei, H. and Peng, J. -C. and Pereira, H. and Peresedov, V. and Peressounko, D. Yu. and Petti, R. and Pinkenburg, C. and Pisani, R. P. and Proissl, M. and Purschke, M. L. and Qu, H. and Rak, J. and Ravinovich, I. and Read, K. F. and Reynolds, R. and Riabov, V. and Riabov, Y. and Richardson, E. and Roach, D. and Roche, G. and Rolnick, S. 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S. and Tserruya, I. and Tsuchimoto, Y. and Tsuji, T. and Vale, C. and van Hecke, H. W. and Vargyas, M. and Vazquez-Zambrano, E. and Veicht, A. and Velkovska, J. and Vertesi, R. and Virius, M. and Vossen, A. and Vrba, V. and Vznuzdaev, E. and Wang, X. R. and Watanabe, D. and Watanabe, K. and Watanabe, Y. and Watanabe, Y. S. and Wei, F. and Wei, R. and White, S. N. and Winter, D. and Wolin, S. and Woody, C. L. and Wysocki, M. and Yamaguchi, Y. L. and Yang, R. and Yanovich, A. and Ying, J. and Yokkaichi, S. and You, Z. and Younus, I. and Yushmanov, I. E. and Zajc, W. A. and Zelenski, A. and Zolin, L.},
  issn         = {1079-7114},
  language     = {eng},
  number       = {15},
  publisher    = {American Physical Society},
  series       = {Physical Review Letters},
  title        = {Evolution of pi(0) Suppression in Au plus Au Collisions from root s(NN)=39 to 200 GeV},
  url          = {http://dx.doi.org/10.1103/PhysRevLett.109.152301},
  volume       = {109},
  year         = {2012},
}