/ hep-ex CERN-PH-EP-2015-328


Leading-order determination of the gluon polarisation using a novel method


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. (DAPNIA, Saclay) ; Anfimov, N.V. (Dubna, JINR) ; Anosov, V. (Dubna, JINR) ; Augustyniak, W. (NCBJ, Swierk) ; Austregesilo, A. (Munich, Tech. U.) ; Azevedo, C.D.R. (Aveiro U.) ; Badelek, B. (Warsaw U.) ; Balestra, F. (INFN, Turin) ; Barth, J. (Bonn U.) ; Beck, R. (Bonn U., HISKP) ; Bedfer, Y. (CERN) ; Bernhard, J. (CERN) ; Bicker, K. (CERN) ; Bielert, E.R. (CERN) ; Birsa, R. (INFN, Trieste) ; Bisplinghoff, J. (Bonn U., HISKP) ; Bodlak, M. (Charles U., Prague) ; Boer, M. (DAPNIA, Saclay) ; Bordalo, P. (Lisbon, IST) ; Bradamante, F. (INFN, Trieste) ; Braun, C. (Erlangen - Nuremberg U.) ; Bressan, A. (INFN, Trieste) ; Buchele, M. (Freiburg U.) ; Chang, W.C. (Taiwan, Inst. Phys.) ; Chiosso, M. (INFN, Turin) ; Choi, I. (Illinois U., Urbana) ; Chung, S.U. (Brookhaven) ; Cicuttin, A. (INFN, Trieste) ; Crespo, M.L. (INFN, Trieste) ; Curiel, Q. (DAPNIA, 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. (Kurchatov Inst., Moscow) ; Doshita, N. (Yamagata U.) ; Duic, V. (Trieste U.) ; Dunnweber, W. (Munich, Tech. U.) ; Dziewiecki, M. (Warsaw U. of Tech.) ; Efremov, A. (Dubna, JINR) ; Eversheim, P.D. (Bonn U., HISKP) ; Eyrich, W. (Erlangen - Nuremberg U.) ; Faessler, M. (Munich, Tech. U.) ; Ferrero, A. (DAPNIA, Saclay) ; Finger, M. (Charles U., Prague) ; M. Finger jr (Charles U., Prague) ; Fischer, H. (Freiburg U.) ; Franco, C. (Lisbon, LIFEP) ; von Hohenesche, N. du Fresne (Mainz U., Inst. Kernphys.) ; Friedrich, J.M. (Munich, Tech. U.) ; Frolov, V. (CERN) ; Fuchey, E. (DAPNIA, Saclay) ; Gautheron, F. (Ruhr U., Bochum) ; Gavrichtchouk, O.P. (Dubna, JINR) ; Gerassimov, S. (Munich, Tech. U.) ; Giordano, F. (Illinois U., Urbana) ; Gnesi, I. (INFN, Turin) ; Gorzellik, M. (Freiburg U.) ; Grabmuller, 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.) ; von Harrach, D. (Mainz U., Inst. Kernphys.) ; Hashimoto, R. (Yamagata U.) ; Heinsius, F.H. (Freiburg U.) ; Heitz, R. (Illinois U., Urbana) ; Herrmann, F. (Freiburg U.) ; Hinterberger, F. (Bonn U., HISKP) ; Horikawa, N. (Chubu U.) ; d'Hose, N. (DAPNIA, Saclay) ; Hsieh, C.Y. (Taiwan, Inst. Phys.) ; Huber, S. (Munich, Tech. U.) ; Ishimoto, S. (KEK, Tsukuba) ; Ivanov, A. (INFN, Turin) ; Ivanshin, Yu. (Dubna, JINR) ; Iwata, T. (Yamagata U.) ; Jahn, R. (Bonn U., HISKP) ; Jary, V. (Prague, Tech. U.) ; Joosten, R. (Bonn U., HISKP) ; Jorg, P. (Freiburg U.) ; Kabuss, E. (Mainz U., Inst. Kernphys.) ; Ketzer, B. (Bonn U., HISKP) ; Khaustov, G.V. (Kurchatov Inst., Moscow) ; Khokhlov, Yu. A. (PNL, Richland) ; Kisselev, Yu. (Dubna, JINR) ; Klein, F. (Bonn U.) ; Klimaszewski, K. (NCBJ, Swierk) ; Koivuniemi, J.H. (Ruhr U., Bochum) ; Kolosov, V.N. (Kurchatov Inst., Moscow) ; Kondo, K. (Yamagata U.) ; Konigsmann, K. (Freiburg U.) ; Konorov, I. (Munich, Tech. U.) ; Konstantinov, V.F. (Kurchatov Inst., Moscow) ; Kotzinian, A.M. (INFN, Turin) ; Kouznetsov, O.M. (Dubna, JINR) ; Kramer, 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. (DAPNIA, Saclay) ; Kurek, K. (NCBJ, Swierk) ; Kurjata, R.P. (Warsaw U. of Tech.) ; Lednev, A.A. (Kurchatov Inst., Moscow) ; Lehmann, A. (Erlangen - Nuremberg U.) ; Levillain, M. (DAPNIA, Saclay) ; Levorato, S. (INFN, Trieste) ; Lichtenstadt, J. (Tel Aviv U.) ; Longo, R. (INFN, Turin) ; Maggiora, A. (INFN, Turin) ; Magnon, A. (DAPNIA, Saclay) ; Makins, N. (Illinois U., Urbana) ; Makke, N. (INFN, Trieste) ; Mallot, G.K. (CERN) ; Marchand, C. (DAPNIA, Saclay) ; Marianski, B. (NCBJ, Swierk) ; Martin, A. (INFN, Trieste) ; Marzec, J. (Warsaw U. of Tech.) ; J.Matou s (Charles U., Prague) ; Matsuda, H. (Yamagata U.) ; Matsuda, T. (Miyazaki U.) ; Meshcheryakov, G.V. (Dubna, JINR) ; Meyer, W. (Ruhr U., Bochum) ; Michigami, T. (Yamagata U.) ; Mikhailov, Yu. V. (Kurchatov Inst., Moscow) ; Mikhasenko, M. (Bonn U., HISKP) ; Miyachi, Y. (Yamagata U.) ; Montuenga, P. (Illinois U., Urbana) ; Nagaytsev, A. (Dubna, JINR) ; Nerling, F. (Mainz U., Inst. Kernphys.) ; Neyret, D. (DAPNIA, Saclay) ; Nikolaenko, V.I. (Kurchatov Inst., Moscow) ; Novy, J. (CERN) ; Nowak, W.D. (Freiburg U.) ; Nukazuka, G. (Yamagata U.) ; Nunes, A.S. (Lisbon, LIFEP) ; 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.) ; M. Pe s (Charles U., Prague) ; Peshekhonov, D.V. (Dubna, JINR) ; Platchkov, S. (DAPNIA, Saclay) ; Pochodzalla, J. (Mainz U., Inst. Kernphys.) ; Polyakov, V.A. (Kurchatov Inst., Moscow) ; Pretz, J. (Aachen, Tech. Hochsch.) ; Quaresma, M. (Lisbon, LIFEP) ; Quintans, C. (Lisbon, LIFEP) ; Ramos, S. (Lisbon, IST) ; Regali, C. (Freiburg U.) ; Reicherz, G. (Ruhr U., Bochum) ; Riedl, C. (Illinois U., Urbana) ; Roskot, M. (Charles U., Prague) ; Rossiyskaya, N.S. (Dubna, JINR) ; Ryabchikov, D.I. (PNL, Richland) ; Rybnikov, A. (Dubna, JINR) ; Rychter, A. (Warsaw U. of Tech.) ; Salac, R. (Prague, Tech. U.) ; Samoylenko, V.D. (Kurchatov Inst., Moscow) ; Sandacz, A. (NCBJ, Swierk) ; 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. (Freiburg U.) ; Schmieden, H. (Bonn U.) ; Schonning, K. (Uppsala U.) ; Schopferer, S. (Freiburg U.) ; Seder, E. (DAPNIA, Saclay) ; Selyunin, A. (Dubna, JINR) ; Shevchenko, O.Yu. (Dubna, JINR) ; Silva, L. (Lisbon, LIFEP) ; Sinha, L. (Matrivani Inst., Calcutta) ; Sirtl, S. (Freiburg U.) ; Slunecka, M. (Dubna, JINR) ; Smolik, J. (Dubna, JINR) ; Sozzi, F. (INFN, Trieste) ; Srnka, A. (Inst. Sci. Instruments, Brno) ; Stolarski, M. (Lisbon, LIFEP) ; Sulc, M. (Liberec Tech. U.) ; Suzuki, H. (Chubu U.) ; Szabelski, A. (NCBJ, Swierk) ; Szameitat, T. (Freiburg U.) ; Sznajder, P. (NCBJ, Swierk) ; Takekawa, S. (INFN, Turin) ; Tasevsky, M. (Dubna, JINR) ; Tessaro, S. (INFN, Trieste) ; Tessarotto, F. (INFN, Trieste) ; Thibaud, F. (DAPNIA, Saclay) ; Tosello, F. (INFN, Turin) ; Tskhay, V. (Lebedev Inst.) ; Uhl, S. (Munich, Tech. U.) ; Veloso, J. (Aveiro U.) ; Virius, M. (Prague, Tech. U.) ; Vondra, J. (Prague, Tech. U.) ; Weisrock, T. (Mainz U., Inst. Kernphys.) ; Wilfert, M. (Mainz U., Inst. Kernphys.) ; Wolbeek, J. ter (Freiburg U.) ; Zaremba, K. (Warsaw U. of Tech.) ; Zavada, P. (Dubna, JINR) ; Zavertyaev, M. (Lebedev Inst.) ; Zemlyanichkina, E. (Dubna, JINR) ; Ziembicki, M. (Warsaw U. of Tech.) ; Zink, A. (Erlangen - Nuremberg U.)

Pages: 14

Abstract: A re-evaluation of the gluon polarisation $\Delta g/g$ in the nucleon is presented, which is based on the measurement of the longitudinal double-spin asymmetry using semi-inclusive events with photon virtuality $Q^2>1~({\rm GeV}/c)^2$. The data were obtained by the COMPASS experiment at CERN using a 160 GeV/$c$ polarised muon beam scattering off a polarised $^6$LiD target. The gluon polarisation is evaluated for three intervals of the nucleon momentum fraction carried by gluons, $x_{\rm g}$, covering the range $0.04 \!<\! x_{ \rm g}\! <\! 0.28$ . A novel method covering the full range in hadron transverse momentum $p_{\rm T}$ and a neural network approach are used. The values obtained at leading order in pQCD do not show any significant dependence on $x_{\rm g}$. Averaged over the three intervals, the result is $\langle \Delta g/g \rangle = 0.113 \pm 0.038_{\rm (stat.)}\pm 0.036_{\rm (syst.)}$ at $\langle x_{\rm g} \rangle \approx 0.10$ and a hard scale of $\mu^2= \langle Q^2 \rangle = 3 ({\rm GeV}/c)^2$. The obtained result suggests that the gluon polarisation is positive in the measured $x_{\rm g}$ range.

Web-Page: http://inspirehep.net/record/1409917/files/fig2.png; http://inspirehep.net/record/1409917/files/fig3.png; http://inspirehep.net/record/1409917/files/fig1.png; http://inspirehep.net/record/1409917/files/fig4a.png; http://inspirehep.net/record/1409917/files/fig4b.png; http://inspirehep.net/record/1409917/files/fig5a.png; http://inspirehep.net/record/1409917/files/fig6b.png; http://inspirehep.net/record/1409917/files/fig6a.png; http://inspirehep.net/record/1409917/files/fig5b.png; http://inspirehep.net/record/1409917/files/arXiv:1512.05053.pdf


Note: *Temporary entry*; 14 pages, 6 figures

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