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Measurement of the Spin Asymmetry in the Photoproduction of Pairs of High- p T Hadrons at HERMES

2000; American Physical Society; Volume: 84; Issue: 12 Linguagem: Inglês

10.1103/physrevlett.84.2584

1092-0145

A. Airapetian, Н. Акопов, M. Amarian, E. C. Aschenauer, Harut Avakian, R. Avakian, A. Avetissian, B. Bains, C. Baumgarten, M. Beckmann, S. Belostotski, J. Belz, T. Benisch, S. Bernreuther, N. Bianchi, J. Blouw, H. Böttcher, A. Borissov, J. Brack, S. Brauksiepe, B. Braun, W. Brückner, A. Brüll, H. J. Bulten, G. P. Capitani, P. Carter, P. Chumney, E. Cisbani, G.R. Court, P. Dalpiaz, E. De Sanctis, D. De Schepper, E. Devitsin, P. K. A. de Witt Huberts, P. Di Nezza, M. Düren, A. Dvoredsky, G. Elbakian, J. Ely, A. Fantoni, M. Ferstl, K. Fiedler, B. W. Filippone, H. Fischer, B. Fox, J. Franz, S. Frullani, M.-A. Funk, Y. Gärber, F. Garibaldi, G. Gavrilov, P. Geiger, V. Gharibyan, A. Golendukhin, G. Graw, O. Grebeniouk, P. W. Green, L. G. Greeniaus, C. Großhauser, M. Guidal, A. Gute, W. Haeberli, O. Hansen, D. Hasch, O. Häusser, F. H. Heinsius, R. Henderson, M. Henoch, R. Hertenberger, Y. Holler, R. J. Holt, W. Hoprich, H. Ihssen, M. Iodice, A. Izotov, H. E. Jackson, A. Jgoun, R. Kaiser, E. Kinney, A. Kisselev, P. Kitching, Hisao Kobayashi, N. Koch, K. Königsmann, M. Kolstein, H. Kolster, В. А. Коротков, W. Korsch, В. Козлов, L. Kramer, M. Kurisuno, G. S. Kyle, W. Lachnit, W. Lorenzon, N. C. R. Makins, F. K. Martens, J. W. Martin, F. Masoli, A.O. Mateos, M. McAndrew, K. McIlhany, R. D. McKeown, F. Meißner, F. Menden, A. Metz, N. Meyners, O. Mikloukho, C. A. Miller, Meredith Miller, R. Milner, A. Most, V. Muccifora, Y. Naryshkin, A. M. Nathan, F. Neunreither, M. Niczyporuk, W.‐D. Nowak, T. G. O’Neill, R. Openshaw, J. Ouyang, B. Owen, S. F. Pate, S. Potashov, D. H. Potterveld, G. Rakness, R. Redwine, A. R. Reolon, R. A. Ristinen, K. Rith, P. Rossi, S. Rudnitsky, M. Ruh, D. Ryckbosch, Y. Sakemi, C. Scarlett, A. Schäfer, Friedrich Schmidt, H. Schmitt, G. Schnell, K. P. Schüler, A. Schwind, J. Anthony Seibert, T.-A. Shibata, K. Shibatani, T. Shin, V. Shutov, C. Simani, A. Simon, K. Sinram, P. Slavich, M. Spengos, E. Steffens, J. Stenger, J. Stewart, U. Stoesslein, M. Sutter, H. Tallini, S. Taroian, A. Terkulov, B. Tipton, M. Tytgat, G. M. Uriuoli, J. van den Brand, J. van den Brand, G. van der Steenhoven, J. van den Brand, M. C. Vetterli, V. Vikhrov, M. G. Vincter, J. Visser, E. Volk, W. Wander, J. Wendland, S. E. Williamson, T. Wise, Kevin B. Woller, S. Yoneyama, H. Zohrabian,

High-Energy Particle Collisions Research

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(h(1))(T)>1.5 GeV/c and p(h(2))(T)>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.