The Spin Structure Function $g_1^{\rm p}$ of the Proton and a Test of the Bjorken Sum Rule
Creators: name: Adolph, C.
name: Akhunzyanov, R.
name: Alexeev, M. G.
name: Alexeev, G. D.
name: Amoroso, A.
name: Andrieux, V.
name: Anosov, V.
name: Austregesilo, A.
name: Azevedo, C.
name: Badelek, B.
name: Balestra, F.
name: Barth, J.
name: Baum, G.
name: Beck, G. R.
name: Bedfer, Y.
name: Bernhard, J.
name: Bicker, K.
name: Bielert, E. R.
name: Birsa, R.
name: Bisplinghoff, J.
name: Bodlak, M.
name: Boer, M.
name: Bordalo, P.
name: Bradamante, F.
name: Braun, C.
name: Bressan, A.
name: Buechele, M.
name: Burtin, E.
name: Capozza, L.
name: Chang, W. -C.
name: Chiosso, M.
name: Choi, I.
name: Chung, S. U.
name: Cicuttin, A.
name: Crespo, M. L.
name: Curiel, Q.
name: Torre, S. Dalla
name: Dasgupta, S. S.
name: Dasgupta, S.
name: Denisov, O. Yu.
name: Dhara, L.
name: Donskov, S. V.
name: Doshita, N.
name: Duic, V.
name: Dziewiecki, M.
name: Efremov, A.
name: Eversheim, P. D.
name: Eyrich, W.
name: Ferrero, A.
name: Finger, M.
name: Finger, M.
name: Fischer, H.
name: Franco, C.
name: von Hohenesche, N. du Fresne
name: Friedrich, J. M.
name: Frolov, V.
name: Fuchey, E.
name: Gautheron, F.
name: Gavrichtchouk, O. P.
name: Gerassimov, S.
name: Giordano, F.
name: Gnesi, I.
name: Gorzellik, M.
name: Grabmüller, S.
name: Grasso, A.
name: Grosse-Perdekamp, M.
name: Grube, B.
name: Grussenmeyer, T.
name: Guskov, A.
name: Haas, F.
name: Hahne, D.
name: von Harrach, D.
name: Hashimoto, R.
name: Heinsius, F. H.
name: Herrmann, F.
name: Hinterberger, F.
name: Horikawa, N.
name: d'Hose, N.
name: Hsieh, C. -Yu
name: Huber, S.
name: Ishimoto, S.
name: Ivanov, A.
name: Ivanshin, Yu.
name: Iwata, T.
name: Jahn, R.
name: Jary, V.
name: Jörg, P.
name: Joosten, R.
name: Kabuß, E.
name: Ketzer, B.
name: Khaustov, G. V.
name: Khokhlov, Yu. A.
name: Kisselev, Yu.
name: Klein, F.
name: Klimaszewski, K.
name: Koivuniemi, J. H.
name: Kolosov, V. N.
name: Kondo, K.
name: Koenigsmann, K.
name: Konorov, I.
name: Konstantinov, V. F.
name: Kotzinian, A. M.
name: Kouznetsov, O.
name: Kraemer, M.
name: Kremser, P.
name: Krinner, F.
name: Kroumchtein, Z. V.
name: Kuchinski, N.
name: Kunne, F.
name: Kurek, K.
name: Kurjata, R. P.
name: Lednev, A. A.
name: Lehmann, A.
name: Levillain, M.
name: Levorato, S.
name: Lichtenstadt, J.
name: Longo, R.
name: Maggiora, A.
name: Magnon, A.
name: Makins, N.
name: Makke, N.
name: Mallot, G. K.
name: Marchand, C.
name: Martin, A.
name: Marzec, J.
name: Matousek, J.
name: Matsuda, H.
name: Matsuda, T.
name: Meshcheryakov, G.
name: Meyer, W.
name: Michigami, T.
name: Mikhailov, Yu. V.
name: Miyachi, Y.
name: Nagaytsev, A.
name: Nagel, T.
name: Nerling, F.
name: Neyret, D.
name: Nikolaenko, V. I.
name: Novy, J.
name: Nowak, W. -D.
name: Nunes, A. S.
name: Olshevsky, A. G.
name: Orlov, I.
name: Ostrick, M.
name: Panzieri, D.
name: Parsamyan, B.
name: Paul, S.
name: Peng, J. -C.
name: Pereira, F.
name: Pesek, M.
name: Peshekhonov, D. V.
name: Platchkov, S.
name: Pochodzalla, J.
name: Polyakov, V. A.
name: Pretz, J.
name: Quaresma, M.
name: Quintans, C.
name: Ramos, S.
name: Regali, C.
name: Reicherz, G.
name: Riedl, C.
name: Rocco, E.
name: Rossiyskaya, N. S.
name: Ryabchikov, D. I.
name: Rychter, A.
name: Samoylenko, V. D.
name: Sandacz, A.
name: Santos, C.
name: Sarkar, S.
name: Savin, I. A.
name: Sbrizzai, G.
name: Schiavon, P.
name: Schmidt, K.
name: Schmieden, H.
name: Schoenning, K.
name: Schopferer, S.
name: Selyunin, A.
name: Shevchenko, O. Yu.
name: Silva, L.
name: Sinha, L.
name: Sirtl, S.
name: Slunecka, M.
name: Sozzi, F.
name: Srnka, A.
name: Stolarski, M.
name: Sulc, M.
name: Suzuki, H.
name: Szabelski, A.
name: Szameitat, T.
name: Sznajder, P.
name: Takekawa, S.
name: ter Wolbeek, J.
name: Tessaro, S.
name: Tessarotto, F.
name: Thibaud, F.
name: Tosello, F.
name: Tskhay, V.
name: Uhl, S.
name: Veloso, J.
name: Virius, M.
name: Weisrock, T.
name: Wilfert, M.
name: Zaremba, K.
name: Zavertyaev, M.
name: Zemlyanichkina, E.
name: Ziembicki, M.
name: Zink, A.
Publisher: name: arXiv
Year: 2015
Subjects: subject: High Energy Physics - Experiment (hep-ex)
subject: High Energy Physics - Phenomenology (hep-ph)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: New results for the double spin asymmetry $A_1^{\rm p}$ and the proton longitudinal spin structure function $g_1^{\rm p}$ are presented. They were obtained by the COMPASS collaboration using polarised 200 GeV muons scattered off a longitudinally polarised NH$_3$ 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 $g_1^{\rm p}(x)$ by about a factor of two in the region $x\lesssim 0.02$. A next-to-leading order QCD fit to the $g_1$ 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 $g_1^{\rm p}$. 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 $g_1^{\rm NS}(x,Q^2)$ yields as ratio of the axial and vector coupling constants $|g_{\rm A}/g_{\rm V}| = 1.22 \pm 0.05~({\rm stat.}) \pm 0.10~({\rm syst.})$, which validates the sum rule to an accuracy of about 9\%.
description: 19 pages, 8 figures and tables