Phys. Rev. Lett.
103,
012003
(2009)
[6 pages]
Gluon-Spin Contribution to the Proton Spin from the Double-Helicity Asymmetry in Inclusive π0 Production in Polarized p+p Collisions at √s=200 GeV
A. Adare et al. PHENIX Collaboration
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A. Adare12, S. Afanasiev26, C. Aidala37, N. N. Ajitanand54, Y. Akiba48,49, H. Al-Bataineh43, J. Alexander54, K. Aoki31,48, L. Aphecetche56, J. Asai48, E. T. Atomssa32, R. Averbeck55, T. C. Awes44, B. Azmoun7, V. Babintsev22, M. Bai6, G. Baksay18, L. Baksay18, A. Baldisseri15, K. N. Barish8, P. D. Barnes34, B. Bassalleck42, A. T. Basye1, S. Bathe8, S. Batsouli44, V. Baublis47, C. Baumann38, A. Bazilevsky7, S. Belikov7,†, R. Bennett55, A. Berdnikov51, Y. Berdnikov51, A. A. Bickley12, J. G. Boissevain34, H. Borel15, K. Boyle55, M. L. Brooks34, H. Buesching7, V. Bumazhnov22, G. Bunce7,49, S. Butsyk34, C. M. Camacho34, S. Campbell55, P. Chand4, B. S. Chang63, W. C. Chang2, J.-L. Charvet15, S. Chernichenko22, C. Y. Chi13, M. Chiu23, I. J. Choi63, R. K. Choudhury4, T. Chujo59, P. Chung54, A. Churyn22, V. Cianciolo44, Z. Citron55, B. A. Cole13, P. Constantin34, M. Csanád17, T. Csörgő28, T. Dahms55, S. Dairaku31,48, K. Das19, G. David7, A. Denisov22, D. d’Enterria32, A. Deshpande49,55, E. J. Desmond7, O. Dietzsch52, A. Dion55, M. Donadelli52, O. Drapier32, A. Drees55, K. A. Drees6, A. K. Dubey62, A. Durum22, D. Dutta4, V. Dzhordzhadze8, Y. V. Efremenko44, J. Egdemir55, F. Ellinghaus12, T. Engelmore13, A. Enokizono33, H. En’yo48,49, S. Esumi59, K. O. Eyser8, B. Fadem39, D. E. Fields42,49, M. Finger9, M. Finger, Jr.9, F. Fleuret32, S. L. Fokin30, Z. Fraenkel62,†, J. E. Frantz55, A. Franz7, A. D. Frawley19, K. Fujiwara48, Y. Fukao31,48, T. Fusayasu41, I. Garishvili57, A. Glenn12, H. Gong55, M. Gonin32, J. Gosset15, Y. Goto48,49, R. Granier de Cassagnac32, N. Grau13, S. V. Greene60, M. Grosse Perdekamp23,49, T. Gunji11, H.-Å. Gustafsson36, A. Hadj Henni56, J. S. Haggerty7, H. Hamagaki11, R. Han46, E. P. Hartouni33, K. Haruna21, E. Haslum36, R. Hayano11, M. Heffner33, T. K. Hemmick55, T. Hester8, X. He20, J. C. Hill25, M. Hohlmann18, W. Holzmann54, K. Homma21, B. Hong29, T. Horaguchi11,48,58, D. Hornback57, S. Huang60, T. Ichihara48,49, R. Ichimiya48, Y. Ikeda59, K. Imai31,48, J. Imrek16, M. Inaba59, D. Isenhower1, M. Ishihara48, T. Isobe11, M. Issah54, A. Isupov26, D. Ivanischev47, B. V. Jacak55,*, J. Jia13, J. Jin13, B. M. Johnson7, K. S. Joo40, D. Jouan45, F. Kajihara11, S. Kametani48, N. Kamihara49, J. Kamin55, J. H. Kang63, J. Kapustinsky34, D. Kawall37,49, A. V. Kazantsev30, T. Kempel25, A. Khanzadeev47, K. M. Kijima21, J. Kikuchi61, B. I. Kim29, D. H. Kim40, D. J. Kim63, E. Kim53, S. H. Kim63, E. Kinney12, K. Kiriluk12, A. Kiss17, E. Kistenev7, J. Klay33, C. Klein-Boesing38, L. Kochenda47, V. Kochetkov22, B. Komkov47, M. Konno59, J. Koster23, A. Kozlov62, A. Král14, A. Kravitz13, G. J. Kunde34, K. Kurita50,48, M. Kurosawa48, M. J. Kweon29, Y. Kwon57, G. S. Kyle43, R. Lacey54, Y. S. Lai13, J. G. Lajoie25, D. Layton23, A. Lebedev25, D. M. Lee34, K. B. Lee29, T. Lee53, M. J. Leitch34, M. A. L. Leite52, B. Lenzi52, P. Liebing49, T. Liška14, A. Litvinenko26, H. Liu43, M. X. Liu34, X. Li10, B. Love60, D. Lynch7, C. F. Maguire60, Y. I. Makdisi6, A. Malakhov26, M. D. Malik42, V. I. Manko30, E. Mannel13, Y. Mao46,48, L. Mašek9,24, H. Masui59, F. Matathias13, M. McCumber55, P. L. McGaughey34, N. Means55, B. Meredith23, Y. Miake59, P. Mikeš24, K. Miki59, A. Milov7, M. Mishra3, J. T. Mitchell7, A. K. Mohanty4, Y. Morino11, A. Morreale8, D. P. Morrison7, T. V. Moukhanova30, D. Mukhopadhyay60, J. Murata50,48, S. Nagamiya27, J. L. Nagle12, M. Naglis62, M. I. Nagy17, I. Nakagawa48,49, Y. Nakamiya21, T. Nakamura21, K. Nakano48,58, J. Newby33, M. Nguyen55, T. Niita59, R. Nouicer5, A. S. Nyanin30, E. O’Brien7, S. X. Oda11, C. A. Ogilvie25, H. Okada31,48, K. Okada49, M. Oka59, Y. Onuki48, A. Oskarsson36, M. Ouchida21, K. Ozawa11, R. Pak5, A. P. T. Palounek34, V. Pantuev55, V. Papavassiliou43, J. Park53, W. J. Park29, S. F. Pate43, H. Pei25, J.-C. Peng23, H. Pereira15, V. Peresedov26, D. Yu. Peressounko30, C. Pinkenburg7, M. L. Purschke7, A. K. Purwar34, H. Qu20, J. Rak42, A. Rakotozafindrabe32, I. Ravinovich62, K. F. Read44,57, S. Rembeczki18, M. Reuter55, K. Reygers38, V. Riabov47, Y. Riabov47, D. Roach60, G. Roche35, S. D. Rolnick8, M. Rosati25, S. S. E. Rosendahl36, P. Rosnet35, P. Rukoyatkin26, P. Ružička24, V. L. Rykov48, B. Sahlmueller38, N. Saito31,48,49, T. Sakaguchi7, S. Sakai59, K. Sakashita48,58, V. Samsonov47, T. Sato59, S. Sawada27, K. Sedgwick8, J. Seele12, R. Seidl23, A. Yu. Semenov25, V. Semenov22, R. Seto8, D. Sharma62, I. Shein22, T.-A. Shibata48,58, K. Shigaki21, M. Shimomura59, K. Shoji31,48, P. Shukla4, A. Sickles7, C. L. Silva52, D. Silvermyr44, C. Silvestre15, K. S. Sim29, B. K. Singh3, C. P. Singh3, V. Singh3, M. Slunečka9, A. Soldatov22, R. A. Soltz33, W. E. Sondheim34, S. P. Sorensen57, I. V. Sourikova7, F. Staley15, P. W. Stankus44, E. Stenlund36, M. Stepanov43, A. Ster28, S. P. Stoll7, T. Sugitate21, C. Suire45, A. Sukhanov5, J. Sziklai28, E. M. Takagui52, A. Taketani48,49, R. Tanabe59, Y. Tanaka41, S. Taneja55, K. Tanida48,49, M. J. Tannenbaum7, A. Taranenko54, P. Tarján16, H. Themann55, T. L. Thomas42, M. Togawa31,48, A. Toia55, L. Tomášek24, Y. Tomita59, H. Torii21,48, R. S. Towell1, V-N. Tram32, I. Tserruya62, Y. Tsuchimoto21, C. Vale25, H. Valle60, H. W. van Hecke34, A. Veicht23, J. Velkovska60, R. Vertesi16, A. A. Vinogradov30, M. Virius14, V. Vrba24, E. Vznuzdaev47, D. Walker55, X. R. Wang43, Y. Watanabe48,49, F. Wei25, J. Wessels38, S. N. White7, S. Williamson23, D. Winter13, C. L. Woody7, M. Wysocki12, W. Xie49, Y. L. Yamaguchi61, K. Yamaura21, R. Yang23, A. Yanovich22, J. Ying20, S. Yokkaichi48,49, G. R. Young44, I. Younus42, I. E. Yushmanov30, W. A. Zajc13, O. Zaudtke38, C. Zhang44, S. Zhou10, and L. Zolin26 (PHENIX Collaboration)
1Abilene Christian University, Abilene, Texas 79699, USA
2Institute of Physics, Academia Sinica, Taipei 11529, Taiwan
3Department of Physics, Banaras Hindu University, Varanasi 221005, India
4Bhabha Atomic Research Centre, Bombay 400 085, India
5Chemistry Department, Brookhaven National Laboratory, Upton, New York 11973-5000, USA
6Collider-Accelerator Department, Brookhaven National Laboratory, Upton, New York 11973-5000, USA
7Physics Department, Brookhaven National Laboratory, Upton, New York 11973-5000, USA
8University of California - Riverside, Riverside, California 92521, USA
9Charles University, Ovocný trh 5, Praha 1, 116 36, Prague, Czech Republic
10China Institute of Atomic Energy (CIAE), Beijing, People’s Republic of China
11Center for Nuclear Study, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033, Japan
12University of Colorado, Boulder, Colorado 80309, USA
13Columbia University, New York, New York 10027 and Nevis Laboratories, Irvington, New York 10533, USA
14Czech Technical University, Zikova 4, 166 36 Prague 6, Czech Republic
15Dapnia, CEA Saclay, F-91191, Gif-sur-Yvette, France
16Debrecen University, H-4010 Debrecen, Egyetem tér 1, Hungary
17ELTE, Eötvös Loránd University, H - 1117 Budapest, Pázmány P. s. 1/A, Hungary
18Florida Institute of Technology, Melbourne, Florida 32901, USA
19Florida State University, Tallahassee, Florida 32306, USA
20Georgia State University, Atlanta, Georgia 30303, USA
21Hiroshima University, Kagamiyama, Higashi-Hiroshima 739-8526, Japan
22IHEP Protvino, State Research Center of Russian Federation, Institute for High Energy Physics, Protvino, 142281, Russia
23University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
24Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 182 21 Prague 8, Czech Republic
25Iowa State University, Ames, Iowa 50011, USA
26Joint Institute for Nuclear Research, 141980 Dubna, Moscow Region, Russia
27KEK, High Energy Accelerator Research Organization, Tsukuba, Ibaraki 305-0801, Japan
28KFKI Research Institute for Particle and Nuclear Physics of the Hungarian Academy of Sciences (MTA KFKI RMKI), H-1525 Budapest 114, POBox 49, Budapest, Hungary
29Korea University, Seoul, 136-701, Korea
30Russian Research Center “Kurchatov Institute”, Moscow, Russia
31Kyoto University, Kyoto 606-8502, Japan
32Laboratoire Leprince-Ringuet, Ecole Polytechnique, CNRS-IN2P3, Route de Saclay, F-91128, Palaiseau, France
33Lawrence Livermore National Laboratory, Livermore, California 94550, USA
34Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
35LPC, Université Blaise Pascal, CNRS-IN2P3, Clermont-Fd, 63177 Aubiere Cedex, France
36Department of Physics, Lund University, Box 118, SE-221 00 Lund, Sweden
37Department of Physics, University of Massachusetts, Amherst, Massachusetts 01003-9337, USA
38Institut für Kernphysik, University of Muenster, D-48149 Muenster, Germany
39Muhlenberg College, Allentown, Pennsylvania 18104-5586, USA
40Myongji University, Yongin, Kyonggido 449-728, Korea
41Nagasaki Institute of Applied Science, Nagasaki-shi, Nagasaki 851-0193, Japan
42University of New Mexico, Albuquerque, New Mexico 87131, USA
43New Mexico State University, Las Cruces, New Mexico 88003, USA
44Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
45IPN-Orsay, Universite Paris Sud, CNRS-IN2P3, BP1, F-91406, Orsay, France
46Peking University, Beijing, People’s Republic of China
47PNPI, Petersburg Nuclear Physics Institute, Gatchina, Leningrad region, 188300, Russia
48RIKEN Nishina Center for Accelerator-Based Science, Wako, Saitama 351-0198, JAPAN
49RIKEN BNL Research Center, Brookhaven National Laboratory, Upton, New York 11973-5000, USA
50Physics Department, Rikkyo University, 3-34-1 Nishi-Ikebukuro, Toshima, Tokyo 171-8501, Japan
51Saint Petersburg State Polytechnic University, Saint Petersburg, Russia
52Universidade de São Paulo, Instituto de Física, Caixa Postal 66318, São Paulo CEP05315-970, Brazil
53System Electronics Laboratory, Seoul National University, Seoul, Korea
54Chemistry Department, Stony Brook University, Stony Brook, SUNY, New York 11794-3400, USA
55Department of Physics and Astronomy, Stony Brook University, SUNY, Stony Brook, New York 11794, USA.
56SUBATECH (Ecole des Mines de Nantes, CNRS-IN2P3, Université de Nantes) BP 20722 - 44307, Nantes, France
57University of Tennessee, Knoxville, Tennessee 37996, USA
58Department of Physics, Tokyo Institute of Technology, Oh-okayama, Meguro, Tokyo 152-8551, Japan
59Institute of Physics, University of Tsukuba, Tsukuba, Ibaraki 305, Japan
60Vanderbilt University, Nashville, Tennessee 37235, USA
61Waseda University, Advanced Research Institute for Science and Engineering, 17 Kikui-cho, Shinjuku-ku, Tokyo 162-0044, Japan
62Weizmann Institute, Rehovot 76100, Israel
63Yonsei University, IPAP, Seoul 120-749, Korea
Received 6 October 2008; published 1 July 2009
The double helicity asymmetry in neutral pion production for pT=1 to 12 GeV/c was measured with the PHENIX experiment to access the gluon-spin contribution, ΔG, to the proton spin. Measured asymmetries are consistent with zero, and at a theory scale of μ2=4 GeV2 a next to leading order QCD analysis gives ΔG[0.02,0.3]=0.2, with a constraint of -0.7<ΔG[0.02,0.3]<0.5 at Δχ2=9 (∼3σ) for the sampled gluon momentum fraction (x) range, 0.02 to 0.3. The results are obtained using predictions for the measured asymmetries generated from four representative fits to polarized deep inelastic scattering data. We also consider the dependence of the ΔG constraint on the choice of the theoretical scale, a dominant uncertainty in these predictions.
© 2009 The American Physical Society
URL:
http://link.aps.org/doi/10.1103/PhysRevLett.103.012003
DOI:
10.1103/PhysRevLett.103.012003
PACS:
13.88.+e, 13.85.Ni, 21.10.Hw, 25.40.Ep
*PHENIX Spokesperson. jacak@skipper.physics.sunysb.edu †Deceased.
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