/ hep-ex CERN-EP-2017-003


First measurement of the Sivers asymmetry for gluons from SIDIS data


Adolph, C. (Erlangen - Nuremberg U.) ; Aghasyan, M. (INFN, Trieste) ; Akhunzyanov, R. (Dubna, JINR) ; Alexeev, M.G. (Turin U.) ; Alexeev, G.D. (Dubna, JINR) ; Amoroso, A. (INFN, Turin) ; Andrieux, V. (IRFU, Saclay) ; Anfimov, N.V. (Dubna, JINR) ; Anosov, V. (Dubna, JINR) ; Antoshkin, A. (Dubna, JINR) ; Augsten, K. (CTU, Prague) ; Augustyniak, W. (Warsaw, Inst. Nucl. Studies) ; Austregesilo, A. (Munich, Tech. U.) ; Azevedo, C.D.R. (Aveiro U.) ; Badełek, B. (Warsaw U.) ; Balestra, F. (INFN, Turin) ; Ball, M. (Bonn U., HISKP) ; Barth, J. (Bonn U.) ; Beck, R. (Bonn U., HISKP) ; Bedfer, Y. (IRFU, Saclay) ; Bernhard, J. (CERN) ; Bicker, K. (CERN) ; Bielert, E.R. (CERN) ; Birsa, R. (INFN, Trieste) ; Bodlak, M. (Charles U.) ; Bordalo, P. (Lisbon, Tech. U.) ; Bradamante, F. (INFN, Trieste) ; Braun, C. (Erlangen - Nuremberg U.) ; Bressan, A. (INFN, Trieste) ; Büchele, M. (Freiburg U.) ; Chang, W.-C. (Taiwan, Inst. Phys.) ; Chatterjee, C. (Matrivani Inst., Calcutta) ; Chiosso, M. (INFN, Turin) ; Choi, I. (Illinois U., Urbana) ; Chung, S.-U. (Pusan Natl. U.) ; Cicuttin, A. (INFN, Trieste) ; Crespo, M.L. (INFN, Trieste) ; Curiel, Q. (IRFU, Saclay) ; Dalla Torre, S. (INFN, Trieste) ; Dasgupta, S.S. (Matrivani Inst., Calcutta) ; Dasgupta, S. (INFN, Trieste) ; Denisov, O.Yu. (INFN, Turin) ; Dhara, L. (Matrivani Inst., Calcutta) ; Donskov, S.V. (Serpukhov, IHEP) ; Doshita, N. (Yamagata U.) ; Dreisbach, Ch. (Munich, Tech. U.) ; Duic, V. (Trieste U.) ; Dünnweber, W. (CFN, Karlsruhe) ; Dziewiecki, M. (Warsaw U., Inst. Radioelect.) ; Efremov, A. (Dubna, JINR) ; Eversheim, P.D. (Bonn U., HISKP) ; Eyrich, W. (Erlangen - Nuremberg U.) ; Faessler, M. (CFN, Karlsruhe) ; Ferrero, A. (IRFU, Saclay) ; Finger, M. (Charles U.) ; Finger, M., Jr. (Charles U.) ; Fischer, H. (Freiburg U.) ; Franco, C. (LIP, Lisbon) ; du Fresne von Hohenesche, N. (CERN) ; Friedrich, J.M. (Munich, Tech. U.) ; Frolov, V. (CERN) ; Fuchey, E. (IRFU, Saclay) ; Gautheron, F. (Ruhr U., Bochum, Inst. Expt. Phys.) ; Gavrichtchouk, O.P. (Dubna, JINR) ; Gerassimov, S. (Munich, Tech. U.) ; Giarra, J. (Mainz U., Inst. Kernphys.) ; Giordano, F. (Illinois U., Urbana) ; Gnesi, I. (INFN, Turin) ; Gorzellik, M. (CFN, Karlsruhe) ; Grabmüller, S. (Munich, Tech. U.) ; Grasso, A. (INFN, Turin) ; Grosse Perdekamp, M. (Illinois U., Urbana) ; Grube, B. (Munich, Tech. U.) ; Grussenmeyer, T. (Freiburg U.) ; Guskov, A. (Dubna, JINR) ; Haas, F. (Munich, Tech. U.) ; Hahne, D. (Bonn U.) ; Hamar, G. (INFN, Trieste) ; von Harrach, D. (Mainz U., Inst. Kernphys.) ; Heinsius, F.H. (Freiburg U.) ; Heitz, R. (Illinois U., Urbana) ; Herrmann, F. (Freiburg U.) ; Horikawa, N. (Chubu U.) ; d'Hose, N. (IRFU, Saclay) ; Hsieh, C.-Y. (Taiwan, Natl. Central U.) ; Huber, S. (Munich, Tech. U.) ; Ishimoto, S. (KEK, Tsukuba) ; Ivanov, A. (INFN, Turin) ; Ivanshin, Yu. (Dubna, JINR) ; Iwata, T. (Yamagata U.) ; Jary, V. (CTU, Prague) ; Joosten, R. (Bonn U., HISKP) ; Jörg, P. (Freiburg U.) ; Kabuß, E. (Mainz U., Inst. Kernphys.) ; Kerbizi, A. (INFN, Trieste) ; Ketzer, B. (Bonn U., HISKP) ; Khaustov, G.V. (Serpukhov, IHEP) ; Khokhlov, Yu.A. (Dubna, JINR) ; Kisselev, Yu. (Dubna, JINR) ; Klein, F. (Bonn U.) ; Klimaszewski, K. (Warsaw, Inst. Nucl. Studies) ; Koivuniemi, J.H. (Illinois U., Urbana) ; Kolosov, V.N. (Serpukhov, IHEP) ; Kondo, K. (Yamagata U.) ; Königsmann, K. (Freiburg U.) ; Konorov, I. (Munich, Tech. U.) ; Konstantinov, V.F. (Serpukhov, IHEP) ; Kotzinian, A.M. (INFN, Turin) ; Kouznetsov, O.M. (Dubna, JINR) ; Krämer, M. (Munich, Tech. U.) ; Kremser, P. (Freiburg U.) ; Krinner, F. (Munich, Tech. U.) ; Kroumchtein, Z.V. (Dubna, JINR) ; Kulinich, Y. (Illinois U., Urbana) ; Kunne, F. (IRFU, Saclay) ; Kurek, K. (Warsaw, Inst. Nucl. Studies) ; Kurjata, R.P. (Warsaw U., Inst. Radioelect.) ; Lednev, A.A. (Serpukhov, IHEP) ; Lehmann, A. (Erlangen - Nuremberg U.) ; Levillain, M. (IRFU, Saclay) ; Levorato, S. (INFN, Trieste) ; Lian, Y.-S. (Taiwan, Natl. Kaohsiung Normal U.) ; Lichtenstadt, J. (Tel Aviv U.) ; Longo, R. (INFN, Turin) ; Maggiora, A. (INFN, Turin) ; Magnon, A. (Illinois U., Urbana) ; Makins, N. (Illinois U., Urbana) ; Makke, N. (INFN, Trieste) ; Mallot, G.K. (CERN) ; Marianski, B. (Warsaw, Inst. Nucl. Studies) ; Martin, A. (INFN, Trieste) ; Marzec, J. (Warsaw U., Inst. Radioelect.) ; Matoušek, J. (INFN, Trieste) ; Matsuda, H. (Yamagata U.) ; Matsuda, T. (Miyazaki U.) ; Meshcheryakov, G.V. (Dubna, JINR) ; Meyer, M. (IRFU, Saclay) ; Meyer, W. (Ruhr U., Bochum, Inst. Expt. Phys.) ; Mikhailov, Yu.V. (Serpukhov, IHEP) ; Mikhasenko, M. (Bonn U., HISKP) ; Mitrofanov, E. (Dubna, JINR) ; Mitrofanov, N. (Dubna, JINR) ; Miyachi, Y. (Yamagata U.) ; Nagaytsev, A. (Dubna, JINR) ; Nerling, F. (Mainz U., Inst. Kernphys.) ; Neyret, D. (IRFU, Saclay) ; Nový, J. (CERN) ; Nowak, W.-D. (Mainz U., Inst. Kernphys.) ; Nukazuka, G. (Yamagata U.) ; Nunes, A.S. (LIP, Lisbon) ; Olshevsky, A.G. (Dubna, JINR) ; Orlov, I. (Dubna, JINR) ; Ostrick, M. (Mainz U., Inst. Kernphys.) ; Panzieri, D. (INFN, Turin) ; Parsamyan, B. (INFN, Turin) ; Paul, S. (Munich, Tech. U.) ; Peng, J.-C. (Illinois U., Urbana) ; Pereira, F. (Aveiro U.) ; Pešek, M. (Charles U.) ; Peshekhonov, D.V. (Dubna, JINR) ; Pierre, N. (IRFU, Saclay) ; Platchkov, S. (IRFU, Saclay) ; Pochodzalla, J. (Mainz U., Inst. Kernphys.) ; Polyakov, V.A. (Serpukhov, IHEP) ; Pretz, J. (Aachen, Tech. Hochsch.) ; Quaresma, M. (LIP, Lisbon) ; Quintans, C. (LIP, Lisbon) ; Ramos, S. (Lisbon, Tech. U.) ; Regali, C. (Freiburg U.) ; Reicherz, G. (Ruhr U., Bochum, Inst. Expt. Phys.) ; Riedl, C. (Illinois U., Urbana) ; Roskot, M. (Charles U.) ; Rogacheva, N.S. (Dubna, JINR) ; Ryabchikov, D.I. (Dubna, JINR) ; Rybnikov, A. (Dubna, JINR) ; Rychter, A. (Warsaw U., Inst. Radioelect.) ; Salac, R. (CTU, Prague) ; Samoylenko, V.D. (Serpukhov, IHEP) ; Sandacz, A. (Warsaw, Inst. Nucl. Studies) ; Santos, C. (INFN, Trieste) ; Sarkar, S. (Matrivani Inst., Calcutta) ; Savin, I.A. (Dubna, JINR) ; Sawada, T. (Taiwan, Inst. Phys.) ; Sbrizzai, G. (INFN, Trieste) ; Schiavon, P. (INFN, Trieste) ; Schmidt, K. (CFN, Karlsruhe) ; Schmieden, H. (Bonn U.) ; Schönning, K. (Uppsala U.) ; Seder, E. (INFN, Trieste) ; Selyunin, A. (Dubna, JINR) ; Silva, L. (LIP, Lisbon) ; Sinha, L. (Matrivani Inst., Calcutta) ; Sirtl, S. (Freiburg U.) ; Slunecka, M. (Dubna, JINR) ; Smolik, J. (Dubna, JINR) ; Srnka, A. (Inst. Sci. Instruments, Brno) ; Steffen, D. (Munich, Tech. U.) ; Stolarski, M. (LIP, Lisbon) ; Subrt, O. (CTU, Prague) ; Sulc, M. (Liberec Tech. U.) ; Suzuki, H. (Chubu U.) ; Szabelski, A. (INFN, Trieste) ; Szameitat, T. (CFN, Karlsruhe) ; Sznajder, P. (Warsaw, Inst. Nucl. Studies) ; Takekawa, S. (INFN, Turin) ; Tasevsky, M. (Dubna, JINR) ; Tessaro, S. (INFN, Trieste) ; Tessarotto, F. (INFN, Trieste) ; Thibaud, F. (IRFU, Saclay) ; Thiel, A. (Bonn U., HISKP) ; Tosello, F. (INFN, Turin) ; Tskhay, V. (Lebedev Inst.) ; Uhl, S. (Munich, Tech. U.) ; Vauth, A. (CERN) ; Veloso, J. (Aveiro U.) ; Virius, M. (CTU, Prague) ; Vondra, J. (CTU, Prague) ; Wallner, S. (Munich, Tech. U.) ; Weisrock, T. (Mainz U., Inst. Kernphys.) ; Wilfert, M. (Mainz U., Inst. Kernphys.) ; ter Wolbeek, J. (CFN, Karlsruhe) ; Zaremba, K. (Warsaw U., Inst. Radioelect.) ; Zavada, P. (Dubna, JINR) ; Zavertyaev, M. (Lebedev Inst.) ; Zemlyanichkina, E. (Dubna, JINR) ; Zhuravlev, N. (Dubna, JINR) ; Ziembicki, M. (Warsaw U., Inst. Radioelect.) ; Zink, A. (Erlangen - Nuremberg U.)

Pages: 18

Abstract: The Sivers function describes the correlation between the transverse spin of a nucleon and the transverse motion of its partons. It was extracted from measurements of the azimuthal asymmetry of hadrons produced in semi-inclusive deep inelastic scattering of leptons off transversely polarised nucleon targets, and it turned out to be non-zero for quarks. In this letter the evaluation of the Sivers asymmetry for gluons in the same process is presented. The analysis method is based on a Monte Carlo simulation that includes three hard processes: photon-gluon fusion, QCD Compton scattering and leading-order virtual-photon absorption process. The Sivers asymmetries of the three processes are simultaneously extracted using the LEPTO event generator and a neural network approach. The method is applied to samples of events containing at least two hadrons with large transverse momentum from the COMPASS data taken with a 160 GeV/$c$ muon beam scattered off transversely polarised deuterons and protons. With a significance of more than two standard deviations a negative value is obtained for the gluon Sivers asymmetry. The result of a similar analysis for a Collins-like asymmetry for gluons is consistent with zero.

Web-Page: http://inspirehep.net/record/1508480/files/plots_deuteron_p2T_deuteron.png; http://inspirehep.net/record/1508480/files/plots_deuteron_p2L_deuteron.png; http://inspirehep.net/record/1508480/files/plots_proton2010_p1L_proton.png; http://inspirehep.net/record/1508480/files/plots_proton2010_p2L_proton.png; http://inspirehep.net/record/1508480/files/plots_proton2010_valid_max_cuts_100k.png; http://inspirehep.net/record/1508480/files/plots_deuteron_CollinsFinalDeuteronForPub.png; http://inspirehep.net/record/1508480/files/plots_proton2010_SiversFinalProtonForPub.png; http://inspirehep.net/record/1508480/files/plots_proton2010_CollinsFinalProtonForPub.png; http://inspirehep.net/record/1508480/files/plots_deuteron_SiversFinalDeuteronForPub.png; http://inspirehep.net/record/1508480/files/plots_LP.png; http://inspirehep.net/record/1508480/files/plots_PGF.png; http://inspirehep.net/record/1508480/files/plots_QCDC.png; http://inspirehep.net/record/1508480/files/plots_MCsystematics_both.png; http://inspirehep.net/record/1508480/files/plots_NN_Triangle_forPub.png; http://inspirehep.net/record/1508480/files/plots_proton2010_Xbj_proton.png; http://inspirehep.net/record/1508480/files/plots_deuteron_Xbj_deuteron.png; http://inspirehep.net/record/1508480/files/plots_proton2010_p2T_proton.png; http://inspirehep.net/record/1508480/files/plots_proton2010_Q_proton.png; http://inspirehep.net/record/1508480/files/plots_deuteron_p1T_deuteron.png; http://inspirehep.net/record/1508480/files/plots_deuteron_Q_deuteron.png; http://inspirehep.net/record/1508480/files/plots_deuteron_p1L_deuteron.png; http://inspirehep.net/record/1508480/files/plots_proton2010_p1T_proton.png; http://inspirehep.net/record/1508480/files/arXiv:1701.02453.pdf


Note: 18 pages, 8 figures

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