/ Experiment-HEP hep-ex/9907020


Measurement of the spin asymmetry in the photoproduction of pairs of high p(T) hadrons at HERMES


Airapetian, A. ; Akopov, N. ; Amarian, M. ; Aschenauer, E.C. ; Avakian, H. ; Avakian, R. ; Avetisian, A. ; Bains, B. ; Baumgarten, C. ; Beckmann, M. ; Belostotski, S. ; Belz, J.E. ; Benisch, T. ; Bernreuther, S. ; Bianchi, N. ; Blouw, J. ; Bottcher, H. ; Borissov, A. ; Brack, J. ; Brauksiepe, S. ; Braun, B. ; Bruckner, W. ; Brull, A. ; Bulten, H.J. ; Capitani, G.P. ; Carter, P. ; Chumney, Pamela R.K. ; Cisbani, E. ; Court, G.R. ; Dalpiaz, P.F. ; De Sanctis, E. ; De Schepper, D. ; Devitsin, E. ; de Witt Huberts, P.K.A. ; Di Nezza, P. ; Duren, M. ; Dvoredsky, A. ; Elbakian, G. ; Ely, J. ; Fantoni, A. ; Ferstl, M. ; Fiedler, K. ; Filippone, B.W. ; Fischer, H. ; Fox, B. ; Franz, J. ; Frullani, S. ; Funk, M.A. ; Garber, Y. ; Garibaldi, F. ; Gavrilov, G. ; Geiger, P. ; Gharibyan, V. ; Golendukhin, A. ; Graw, G. ; Grebeniouk, O. ; Green, P.W. ; Greeniaus, L.G. ; Grosshauser, C. ; Guidal, M. ; Gute, A. ; Haeberli, W. ; Hansen, J.O. ; Hasch, D. ; Heinsius, F.H. ; Henderson, R. ; Henoch, M. ; Hertenberger, R. ; Holler, Y. ; Holt, R.J. ; Hoprich, W. ; Ihssen, H. ; Iodice, M. ; Izotov, A. ; Jackson, H.E. ; Kaiser, R. ; Kinney, E. ; Kisselev, A. ; Kitching, P. ; Kobayashi, H. ; Koch, N. ; Konigsmann, Kay ; Kolstein, M. ; Kolster, H. ; Korotkov, V. ; Korsch, W. ; Kozlov, V. ; Kramer, L.H. ; Kurisuno, M. ; Kyle, G. ; Lachnit, W. ; Lorenzon, W. ; Makins, N.C.R. ; Martens, F.K. ; Martin, J.W. ; Mateos, A. ; McAndrew, M. ; McIlhany, Kevin L. ; McKeown, R.D. ; Meissner, F. ; Menden, F.M. ; Meyners, N. ; Mikloukho, O. ; Miller, C.A. ; Miller, M.A. ; Milner, R. ; Most, A. ; Muccifora, V. ; Naryshkin, Y. ; Nathan, A.M. ; Neunreither, F. ; Niczyporuk, M. ; Nowak, W.D. ; O'Neill, T.G. ; Ouyang, J. ; Owen, B.R. ; Pate, S.F. ; Potashov, S. ; Potterveld, David H. ; Rakness, G. ; Redwine, R. ; Reolon, A.R. ; Ristinen, R. ; Rith, K. ; Rossi, P. ; Rudnitsky, S. ; Ruh, M. ; Ryckbosch, D. ; Sakemi, Y. ; Scarlett, C. ; Schafer, A. ; Schmidt, F. ; Schmitt, H. ; Schnell, G. ; Schuler, K.P. ; Schwind, A. ; Seibert, J. ; Shibata, T.A. ; Shibatani, K. ; Shin, T. ; Shutov, V. ; Simani, C. ; Simon, A. ; Sinram, K. ; Slavich, P. ; Spengos, M. ; Steffens, E. ; Stenger, J. ; Stewart, J. ; Stoesslein, U. ; Sutter, M. ; Tallini, H. ; Taroian, S. ; Terkulov, A. ; Tipton, B. ; Tytgat, M. ; Urciuoli, G.M. ; van de Vyver, R. ; van den Brand, J.F.J. ; van der Steenhoven, G. ; van Hunen, J.J. ; Vetterli, M.C. ; Vikhrov, V. ; Vincter, M.G. ; Visser, J. ; Volk, E. ; Wander, W. ; Wendland, J. ; Williamson, S.E. ; Wise, T. ; Woller, K. ; Yoneyama, S. ; Zohrabian, H.

Published in: Phys.Rev.Lett.
Year: 2000
Vol.: 84
Page No: 2584-2588
Pages: 5

Abstract: We present a measurement of the longitudinal spin asymmetry A_|| in photoproduction of pairs of hadrons with high transverse momentum p_T. Data were accumulated by the HERMES experiment using a 27.5 GeV polarized positron beam and a polarized hydrogen target internal to the HERA storage ring. For h+h- pairs with p_T^h_1 > 1.5 GeV/c and p_T^h_2 > 1.0 GeV/c, the measured asymmetry is A_|| = -0.28 +/- 0.12 (stat.) +/- 0.02 (syst.). This negative value is in contrast to the positive asymmetries typically measured in deep inelastic scattering from protons, and is interpreted to arise from a positive gluon polarization.

Web-Page: http://www.adsabs.harvard.edu/abs/2000PhRvL..84.2584A; http://dx.doi.org/10.1103/PhysRevLett.84.2584; http://link.aps.org/abstract/PRL/V84/P02584; http://durpdg.dur.ac.uk/cgi-hepdata/hepreac/4126106

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