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arXiv · 1202.4064

Leading order determination of the gluon polarisation from DIS events with high-p_T hadron pairs

C. Adolph·M. G. Alekseev·V. Yu. Alexakhin·Yu. Alexandrov·G. D. Alexeev·A. Amoroso·A. A. Antonov·A. Austregesilo·B. Badelek·F. Balestra·J. Barth·G. Baum·Y. Bedfer·J. Bernhard·R. Bertini·M. Bettinelli·K. Bicker·J. Bieling·R. Birsa·J. Bisplinghoff·P. Bordalo·F. Bradamante·C. Braun·A. Bravar·A. Bressan·E. Burtin·D. Chaberny·M. Chiosso·S. U. Chung·A. Cicuttin·M. L. Crespo·S. Dalla Torre·S. Das·S. S. Dasgupta·O. Yu. Denisov·L. Dhara·S. V. Donskov·N. Doshita·V. Duic·W. Duennweber·M. Dziewiecki·A. Efremov·C. Elia·P. D. Eversheim·W. Eyrich·M. Faessler·A. Ferrero·A. Filin·M. Finger·M. Finger jr.·H. Fischer·C. Franco·N. du Fresne von Hohenesche·J. M. Friedrich·R. Garfagnini·F. Gautheron·O. P. Gavrichtchouk·R. Gazda·S. Gerassimov·R. Geyer·M. Giorgi·I. Gnesi·B. Gobbo·S. Goertz·S. Grabmueller·A. Grasso·B. Grube·R. Gushterski·A. Guskov·T. Guthoerl·F. Haas·D. von Harrach·S. Hedicke·F. H. Heinsius·F. Herrmann·C. Hess·F. Hinterberger·N. Horikawa·Ch. Hoeppner·N. d'Hose·S. Huber·S. Ishimoto·O. Ivanov·Yu. Ivanshin·T. Iwata·R. Jahn·P. Jasinski·R. Joosten·E. Kabuss·D. Kang·B. Ketzer·G. V. Khaustov·Yu. A. Khokhlov·Yu. Kisselev·F. Klein·K. Klimaszewski·S. Koblitz·J. H. Koivuniemi·V. N. Kolosov·K. Kondo
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Abstract

We present a determination of the gluon polarisation Delta g/g in the nucleon, based on the longitudinal double-spin asymmetry of DIS events with a pair of large transverse-momentum hadrons in the final state. The data were obtained by the COMPASS experiment at CERN using a 160 GeV/c polarised muon beam scattering off a polarised ^6LiD target. The gluon polarisation is evaluated by a Neural Network approach for three intervals of the gluon momentum fraction x_g covering the range 0.04 < x_g < 0.27. The values obtained at leading order in QCD do not show any significant dependence on x_g. Their average is Delta g/g = 0.125 +/- 0.060 (stat.) +/- 0.063 (syst.) at x_g=0.09 and a scale of mu^2 = 3 (GeV/c)^2.

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C. Adolph, M. G. Alekseev, V. Yu. Alexakhin, Yu. Alexandrov, G. D. Alexeev, A. Amoroso, A. A. Antonov, A. Austregesilo, B. Badelek, F. Balestra, J. Barth, G. Baum, Y. Bedfer, J. Bernhard, R. Bertini, M. Bettinelli, K. Bicker, J. Bieling, R. Birsa, J. Bisplinghoff, P. Bordalo, F. Bradamante, C. Braun, A. Bravar, A. Bressan, E. Burtin, D. Chaberny, M. Chiosso, S. U. Chung, A. Cicuttin, M. L. Crespo, S. Dalla Torre, S. Das, S. S. Dasgupta, O. Yu. Denisov, L. Dhara, S. V. Donskov, N. Doshita, V. Duic, W. Duennweber, M. Dziewiecki, A. Efremov, C. Elia, P. D. Eversheim, W. Eyrich, M. Faessler, A. Ferrero, A. Filin, M. Finger, M. Finger jr., H. Fischer, C. Franco, N. du Fresne von Hohenesche, J. M. Friedrich, R. Garfagnini, F. Gautheron, O. P. Gavrichtchouk, R. Gazda, S. Gerassimov, R. Geyer, M. Giorgi, I. Gnesi, B. Gobbo, S. Goertz, S. Grabmueller, A. Grasso, B. Grube, R. Gushterski, A. Guskov, T. Guthoerl, F. Haas, D. von Harrach, S. Hedicke, F. H. Heinsius, F. Herrmann, C. Hess, F. Hinterberger, N. Horikawa, Ch. Hoeppner, N. d'Hose, S. Huber, S. Ishimoto, O. Ivanov, Yu. Ivanshin, T. Iwata, R. Jahn, P. Jasinski, R. Joosten, E. Kabuss, D. Kang, B. Ketzer, G. V. Khaustov, Yu. A. Khokhlov, Yu. Kisselev, F. Klein, K. Klimaszewski, S. Koblitz, J. H. Koivuniemi, V. N. Kolosov, K. Kondo. 2012-02-18. Leading order determination of the gluon polarisation from DIS events with high-p_T hadron pairs. https://doi.org/10.1016/j.physletb.2012.11.056

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