The spin-dependent structure function of the proton g1p and a test of the Bjorken sum rule

M. G. Alekseev, V. Yu Alexakhin, Yu Alexandrov, G. D. Alexeev, A. Amoroso, A. Austregesilo, B. Badełek, F. Balestra, J. Ball, J. Barth, G. Baum, Y. Bedfer, J. Bernhard, R. Bertini, M. Bettinelli, R. Birsa, J. Bisplinghoff, P. Bordalo, F. Bradamante, A. BravarA. Bressan, G. Brona, E. Burtin, M. P. Bussa, D. Chaberny, D. Čotić, M. Chiosso, S. U. Chung, A. Cicuttin, M. Colantoni, M. L. Crespo, S. Dalla Torre, S. Das, S. S. Dasgupta, O. Yu Denisov, L. Dhara, V. Diaz, S. V. Donskov, N. Doshita, V. Duic, W. Dünnweber, A. Efremov, A. El Alaoui, P. D. Eversheim, W. Eyrich, M. Faessler, A. Ferrero, A. Filin, M. Finger, M. Finger, H. Fischer, C. Franco, J. M. Friedrich, R. Garfagnini, F. Gautheron, O. P. Gavrichtchouk, R. Gazda, S. Gerassimov, R. Geyer, M. Giorgi, I. Gnesi, B. Gobbo, S. Goertz, S. Grabmüller, A. Grasso, B. Grube, R. Gushterski, A. Guskov, F. Haas, D. von Harrach, T. Hasegawa, F. H. Heinsius, R. Hermann, F. Herrmann, C. Heß, F. Hinterberger, N. Horikawa, Ch Höppner, N. d'Hose, C. Ilgner, S. Ishimoto, O. Ivanov, Yu Ivanshin, T. Iwata, R. Jahn, P. Jasinski, G. Jegou, R. Joosten, E. Kabuß, W. Käfer, D. Kang, B. Ketzer, G. V. Khaustov, Yu A. Khokhlov, Yu Kisselev, F. Klein, K. Klimaszewski, S. Koblitz, J. H. Koivuniemi, V. N. Kolosov, K. Kondo, K. Königsmann, R. Konopka, I. Konorov, V. F. Konstantinov, A. Korzenev, A. M. Kotzinian, O. Kouznetsov, K. Kowalik, M. Krämer, A. Kral, Z. V. Kroumchtein, R. Kuhn, F. Kunne, K. Kurek, L. Lauser, J. M. Le Goff, A. A. Lednev, A. Lehmann, S. Levorato, J. Lichtenstadt, T. Liska, A. Maggiora, M. Maggiora, A. Magnon, G. K. Mallot, A. Mann, C. Marchand, J. Marroncle, A. Martin, J. Marzec, F. Massmann, T. Matsuda, W. Meyer, T. Michigami, Yu V. Mikhailov, M. A. Moinester, A. Mutter, A. Nagaytsev, T. Nagel, J. Nassalski, T. Negrini, F. Nerling, S. Neubert, D. Neyret, V. I. Nikolaenko, A. S. Nunes, A. G. Olshevsky, M. Ostrick, A. Padee, R. Panknin, D. Panzieri, B. Parsamyan, S. Paul, B. Pawlukiewicz-Kaminska, E. Perevalova, G. Pesaro, D. V. Peshekhonov, G. Piragino, S. Platchkov, J. Pochodzalla, J. Polak, V. A. Polyakov, G. Pontecorvo, J. Pretz, C. Quintans, J. F. Rajotte, S. Ramos, V. Rapatsky, G. Reicherz, A. Richter, F. Robinet, E. Rocco, E. Rondio, D. I. Ryabchikov, V. D. Samoylenko, A. Sandacz, H. Santos, M. G. Sapozhnikov, S. Sarkar, I. A. Savin, G. Sbrizzai, P. Schiavon, C. Schill, T. Schlüter, L. Schmitt, S. Schopferer, W. Schröder, O. Yu Shevchenko, H. W. Siebert, L. Silva, L. Sinha, A. N. Sissakian, M. Slunecka, G. I. Smirnov, S. Sosio, F. Sozzi, A. Srnka, M. Stolarski, M. Sulc, R. Sulej, S. Takekawa, S. Tessaro, F. Tessarotto, A. Teufel, L. G. Tkatchev, S. Uhl, I. Uman, M. Virius, N. V. Vlassov, A. Vossen, Q. Weitzel, R. Windmolders, W. Wiślicki, H. Wollny, K. Zaremba, M. Zavertyaev, E. Zemlyanichkina, M. Ziembicki, J. Zhao, N. Zhuravlev, A. Zvyagin

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Abstract

The inclusive double-spin asymmetry, A1p, has been measured at COMPASS in deep-inelastic polarised muon scattering off a large polarised NH3 target. The data, collected in the year 2007, cover the range Q2 > 1 (GeV / c)2, 0.004 < x < 0.7 and improve the statistical precision of g1p (x) by a factor of two in the region x < 0.02. The new proton asymmetries are combined with those previously published for the deuteron to extract the non-singlet spin-dependent structure function g1NS (x, Q2). The isovector quark density, Δ q3 (x, Q2), is evaluated from a NLO QCD fit of g1NS. The first moment of Δ q3 is in good agreement with the value predicted by the Bjorken sum rule and corresponds to a ratio of the axial and vector coupling constants | gA / gV | = 1.28 ± 0.07 (stat .) ± 0.10 (syst.).

Original languageEnglish
Pages (from-to)466-472
Number of pages7
JournalPhysics Letters B
Volume690
Issue number5
DOIs
StatePublished - 5 Jul 2010

Keywords

  • Bjorken sum rule
  • COMPASS
  • Deep inelastic scattering
  • QCD analysis
  • Spin
  • Structure function

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