First measurement of the Sivers asymmetry for gluons from SIDIS data

The Sivers function describes the correlation between the transverse spin of a nucleon and the transverse motion of its partons. For quarks, it was studied in previous measurements of the azimuthal asymmetry of hadrons produced in semi-inclusive deep inelastic scattering of leptons off transversely...

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Detalles Bibliográficos
Autores principales: Adolph, C., Aghasyan, M., Akhunzyanov, R., Alexeev, M.G., Alexeev, G.D., Amoroso, A., Andrieux, V., Anfimov, N.V., Anosov, V., Antoshkin, A., Augsten, K., Augustyniak, W., Austregesilo, A., Azevedo, C.D.R., Badełek, B., Balestra, F., Ball, M., Barth, J., Beck, R., Bedfer, Y., Bernhard, J., Bicker, K., Bielert, E.R., Birsa, R., Bodlak, M., Bordalo, P., Bradamante, F., Braun, C., Bressan, A., Büchele, M., Chang, W.-C., Chatterjee, C., Chiosso, M., Choi, I., Chung, S.-U., Cicuttin, A., Crespo, M.L., Curiel, Q., Dalla Torre, S., Dasgupta, S.S., Dasgupta, S., Denisov, O.Yu., Dhara, L., Donskov, S.V., Doshita, N., Dreisbach, Ch., Duic, V., Dünnweber, W., Dziewiecki, M., Efremov, A., Eversheim, P.D., Eyrich, W., Faessler, M., Ferrero, A., Finger, M., Finger, M., Jr., Fischer, H., Franco, C., du Fresne von Hohenesche, N., Friedrich, J.M., Frolov, V., Fuchey, E., Gautheron, F., Gavrichtchouk, O.P., Gerassimov, S., Giarra, J., Giordano, F., Gnesi, I., Gorzellik, M., Grabmüller, S., Grasso, A., Grosse Perdekamp, M., Grube, B., Grussenmeyer, T., Guskov, A., Haas, F., Hahne, D., Hamar, G., von Harrach, D., Heinsius, F.H., Heitz, R., Herrmann, F., Horikawa, N., d'Hose, N., Hsieh, C.-Y., Huber, S., Ishimoto, S., Ivanov, A., Ivanshin, Yu., Iwata, T., Jary, V., Joosten, R., Jörg, P., Kabuß, E., Kerbizi, A., Ketzer, B., Khaustov, G.V., Khokhlov, Yu.A., Kisselev, Yu., Klein, F., Klimaszewski, K., Koivuniemi, J.H., Kolosov, V.N., Kondo, K., Königsmann, K., Konorov, I., Konstantinov, V.F., Kotzinian, A.M., Kouznetsov, O.M., Krämer, M., Kremser, P., Krinner, F., Kroumchtein, Z.V., Kulinich, Y., Kunne, F., Kurek, K., Kurjata, R.P., Lednev, A.A., Lehmann, A., Levillain, M., Levorato, S., Lian, Y.-S., Lichtenstadt, J., Longo, R., Maggiora, A., Magnon, A., Makins, N., Makke, N., Mallot, G.K., Marianski, B., Martin, A., Marzec, J., Matoušek, J., Matsuda, H., Matsuda, T., Meshcheryakov, G.V., Meyer, M., Meyer, W., Mikhailov, Yu.V., Mikhasenko, M., Mitrofanov, E., Mitrofanov, N., Miyachi, Y., Nagaytsev, A., Nerling, F., Neyret, D., Nový, J., Nowak, W.-D., Nukazuka, G., Nunes, A.S., Olshevsky, A.G., Orlov, I., Ostrick, M., Panzieri, D., Parsamyan, B., Paul, S., Peng, J.-C., Pereira, F., Pešek, M., Peshekhonov, D.V., Pierre, N., Platchkov, S., Pochodzalla, J., Polyakov, V.A., Pretz, J., Quaresma, M., Quintans, C., Ramos, S., Regali, C., Reicherz, G., Riedl, C., Roskot, M., Rogacheva, N.S., Ryabchikov, D.I., Rybnikov, A., Rychter, A., Salac, R., Samoylenko, V.D., Sandacz, A., Santos, C., Sarkar, S., Savin, I.A., Sawada, T., Sbrizzai, G., Schiavon, P., Schmidt, K., Schmieden, H., Schönning, K., Seder, E., Selyunin, A., Silva, L., Sinha, L., Sirtl, S., Slunecka, M., Smolik, J., Srnka, A., Steffen, D., Stolarski, M., Subrt, O., Sulc, M., Suzuki, H., Szabelski, A., Szameitat, T., Sznajder, P., Takekawa, S., Tasevsky, M., Tessaro, S., Tessarotto, F., Thibaud, F., Thiel, A., Tosello, F., Tskhay, V., Uhl, S., Vauth, A., Veloso, J., Virius, M., Vondra, J., Wallner, S., Weisrock, T., Wilfert, M., ter Wolbeek, J., Zaremba, K., Zavada, P., Zavertyaev, M., Zemlyanichkina, E., Zhuravlev, N., Ziembicki, M., Zink, A.
Lenguaje:eng
Publicado: 2017
Materias:
Particle Physics - Experiment
hep-ph
Particle Physics - Phenomenology
hep-ex
Acceso en línea:https://dx.doi.org/10.1016/j.physletb.2017.07.018
http://cds.cern.ch/record/2240191
Descripción
Sumario:The Sivers function describes the correlation between the transverse spin of a nucleon and the transverse motion of its partons. For quarks, it was studied in previous measurements of the azimuthal asymmetry of hadrons produced in semi-inclusive deep inelastic scattering of leptons off transversely polarised nucleon targets, and it was found to be non-zero. In this letter the evaluation of the Sivers asymmetry for gluons is presented. The contribution of the photon–gluon fusion subprocess is enhanced by requiring two high transverse-momentum hadrons. The analysis method is based on a Monte Carlo simulation that includes three hard processes: photon–gluon fusion, QCD Compton scattering and the 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 about 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.

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