The spin structure function gp1 of the proton and a test of the Bjorken sum rule

C. Adolph, R. Akhunzyanov, M. G. Alexeev, G. D. Alexeev, A. Amoroso, V. Andrieux, V. Anosov, A. Austregesilo, C. Azevedo, B. Badełek, F. Balestra, J. Barth, G. Baum, R. Beck, Y. Bedfer, J. Bernhard, K. Bicker, E. R. Bielert, R. Birsa, J. BisplinghoffM. Bodlak, M. Boer, P. Bordalo, F. Bradamante, C. Braun, A. Bressan, M. Büchele, E. Burtin, L. Capozza, W. C. Chang, M. Chiosso, I. Choi, S. U. Chung, A. Cicuttin, M. L. Crespo, Q. Curiel, S. Dalla Torre, S. S. Dasgupta, S. Dasgupta, O. Yu Denisov, L. Dhara, S. V. Donskov, N. Doshita, V. Duic, M. Dziewiecki, A. Efremov, P. D. Eversheim, W. Eyrich, A. Ferrero, M. Finger, M. Finger, H. Fischer, C. Franco, N. du Fresne von Hohenesche, J. M. Friedrich, V. Frolov, E. Fuchey, F. Gautheron, O. P. Gavrichtchouk, S. Gerassimov, F. Giordano, I. Gnesi, M. Gorzellik, S. Grabmüller, A. Grasso, M. Grosse-Perdekamp, B. Grube, T. Grussenmeyer, A. Guskov, F. Haas, D. Hahne, D. von Harrach, R. Hashimoto, F. H. Heinsius, F. Herrmann, F. Hinterberger, N. Horikawa, N. d'Hose, C. Yu Hsieh, S. Huber, S. Ishimoto, A. Ivanov, Yu Ivanshin, T. Iwata, R. Jahn, V. Jary, P. Jörg, R. Joosten, E. Kabuß, B. Ketzer, G. V. Khaustov, Yu A. Khokhlov, Yu Kisselev, F. Klein, K. Klimaszewski, J. H. Koivuniemi, V. N. Kolosov, K. Kondo, K. Königsmann, I. Konorov, V. F. Konstantinov, A. M. Kotzinian, O. Kouznetsov, M. Krämer, P. Kremser, F. Krinner, Z. V. Kroumchtein, N. Kuchinski, F. Kunne, K. Kurek, R. P. Kurjata, A. A. Lednev, A. Lehmann, M. Levillain, S. Levorato, J. Lichtenstadt, R. Longo, A. Maggiora, A. Magnon, N. Makins, N. Makke, G. K. Mallot, C. Marchand, A. Martin, J. Marzec, J. Matousek, H. Matsuda, T. Matsuda, G. Meshcheryakov, W. Meyer, T. Michigami, Yu V. Mikhailov, Y. Miyachi, A. Nagaytsev, T. Nagel, F. Nerling, D. Neyret, V. I. Nikolaenko, J. Novy, W. D. Nowak, A. S. Nunes, A. G. Olshevsky, I. Orlov, M. Ostrick, D. Panzieri, B. Parsamyan, S. Paul, J. C. Peng, F. Pereira, M. Pesek, D. V. Peshekhonov, S. Platchkov, J. Pochodzalla, V. A. Polyakov, J. Pretz, M. Quaresma, C. Quintans, S. Ramos, C. Regali, G. Reicherz, C. Riedl, E. Rocco, N. S. Rossiyskaya, D. I. Ryabchikov, A. Rychter, V. D. Samoylenko, A. Sandacz, C. Santos, S. Sarkar, I. A. Savin, G. Sbrizzai, P. Schiavon, K. Schmidt, H. Schmieden, K. Schönning, S. Schopferer, A. Selyunin, O. Yu Shevchenko, L. Silva, L. Sinha, S. Sirtl, M. Slunecka, F. Sozzi, A. Srnka, M. Stolarski, M. Sulc, H. Suzuki, A. Szabelski, T. Szameitat, P. Sznajder, S. Takekawa, J. ter Wolbeek, S. Tessaro, F. Tessarotto, F. Thibaud, F. Tosello, V. Tskhay, S. Uhl, J. Veloso, M. Virius, T. Weisrock, M. Wilfert, R. Windmolders, K. Zaremba, M. Zavertyaev, E. Zemlyanichkina, M. Ziembicki, A. Zink

Research output: Contribution to journalArticle

Abstract

New results for the double spin asymmetry Ap1 and the proton longitudinal spin structure function g1p are presented. They were obtained by the COMPASS Collaboration using polarised 200 GeV muons scattered off a longitudinally polarised NH3 target. The data were collected in 2011 and complement those recorded in 2007 at 160 GeV, in particular at lower values of x. They improve the statistical precision of gp1(x) by about a factor of two in the region x ≲0.02. A next-to-leading order QCD fit to the g1 world data is performed. It leads to a new determination of the quark spin contribution to the nucleon spin, δσ, ranging from 0.26 to 0.36, and to a re-evaluation of the first moment of g1p. The uncertainty of δσ is mostly due to the large uncertainty in the present determinations of the gluon helicity distribution. A new evaluation of the Bjorken sum rule based on the COMPASS results for the non-singlet structure function gNS1(x,Q2) yields as ratio of the axial and vector coupling constants |gA/gV|=1.22 ± 0.05 (stat.) ± 0.10 (syst.), which validates the sum rule to an accuracy of about 9%.

Original languageEnglish (US)
Pages (from-to)18-28
Number of pages11
JournalPhysics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
Volume753
DOIs
StatePublished - Feb 10 2016

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ASJC Scopus subject areas

  • Nuclear and High Energy Physics

Cite this

Adolph, C., Akhunzyanov, R., Alexeev, M. G., Alexeev, G. D., Amoroso, A., Andrieux, V., Anosov, V., Austregesilo, A., Azevedo, C., Badełek, B., Balestra, F., Barth, J., Baum, G., Beck, R., Bedfer, Y., Bernhard, J., Bicker, K., Bielert, E. R., Birsa, R., ... Zink, A. (2016). The spin structure function gp1 of the proton and a test of the Bjorken sum rule. Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 753, 18-28. https://doi.org/10.1016/j.physletb.2015.11.064