Scaling violations and determination of alpha(s) from jet production in gamma p interactions at HERA

Differential cross sections for jet photoproduction in the reaction ep --> e jet X have been measured with the ZEUS detector at HERA using 82.2 pb(-1) of integrated luminosity. Inclusive jet cross sections are presented as a function of the jet transverse energy, E-T(jet), for jets with E-T(jet) > 17 GeV and pseudorapidity -1 < eta(jet) < 2.5, in the gammap centre-of-mass-energy range 142 < Wgammap < 293 GeV. Scaled jet invariant cross sections are presented as a function of the dimensionless variable x(T) equivalent to 2E(T)(jet)/W-gammap for (W-gammap) = 180 and 255 GeV: Next-to-leading-order QCD calculations give a good description of the measured differential cross sections in both magnitude and shape. The ratio of scaled jet invariant cross sections at the two (Wgammap) values shows clear non-scaling behaviour. A value for the strong coupling constant of alpha(s) (M-Z) = 0.1224 +/- 0.0001(stat.)(-0.0019)(+0.0022)(exp.)(-0.0042)(+0.0054)(th.) has been extracted from a QCD analysis of the measured dsigma/dE(T)(jet). The variation of sigma(s) with E-T(jet) is in good agreement with the running of sigma(s) as predicted by QCD. (C) 2003 Published by Elsevier Science B.V. RI De Pasquale, Salvatore/B-9165-2008; Wing, Matthew/C-2169-2008; Doyle, Anthony/C-5889-2009; collins-tooth, christopher/A-9201-2012; Ferrando, James/A-9192-2012; Gladilin, Leonid/B-5226-2011; Golubkov, Yury/E-1643-2012

Differential cross sections for jet photoproduction in the reaction ep --> e jet X have been measured with the ZEUS detector at HERA using 82.2 pb(-1) of integrated luminosity. Inclusive jet cross sections are presented as a function of the jet transverse energy, E(T)(jet), for jets with E(T)(jet) > 17 GeV and pseudorapidity -1 < eta(jet) < 2.5, in the gammap centre-of-mass-energy range 142 < Wgammap < 293 GeV. Scaled jet invariant cross sections are presented as a function of the dimensionless variable x(T) equivalent to 2E(T)(jet)/W(gammap) for (W(gammap)) = 180 and 255 GeV: Next-to-leading-order QCD calculations give a good description of the measured differential cross sections in both magnitude and shape. The ratio of scaled jet invariant cross sections at the two (Wgammap) values shows clear non-scaling behaviour. A value for the strong coupling constant of alpha(s) (M(Z)) = 0.1224 +/- 0.0001(stat.)(-0.0019)(+0.0022)(exp.)(-0.0042)(+0.0054)(th.) has been extracted from a QCD analysis of the measured dsigma/dE(T)(jet). The variation of sigma(s) with E(T)(jet) is in good agreement with the running of sigma(s) as predicted by QCD. (C) 2003 Published by Elsevier Science B.V.