High-E_T inclusive jet cross sections in photoproduction at HERA

Abstract

Inclusive jet differential cross sections for the reaction e"+p#->#e"++jet+X with quasi-real photons have been measured with the ZEUS detector at HERA. These cross sections are given for the photon-proton centre-of-mass energy interval 134<W<277 GeV and jet pseudorapidity in the range -1<#eta#"j"e"t<2 in the laboratory frame. The results are presented for three cone radii in the #eta#-#phi# plane, R=1.0, 0.7 and 0.5. Measurements of d#sigma#/d#eta#"j"e"t above various jet-transverse-energy thresholds up to 25 GeV and in three ranges of W are presented and compared to next-to-leading order (NLO) QCD calculations. For jets defined with R=1.0 differences between data and NLO calculations are seen at high #eta#"j"e"t and low E_T"j"e"t. The measured cross sections for jets defined with R=0.7 are well described by the calculations in the entire measured range of #eta#"j"e"t and E_T"j"e"t. The inclusive jet cross section for E_T"j"e"t>21 GeV is consistent with an approximately linear variation with the cone radius R in the range between 0.5 and 1.0, and with NLO calculations. (orig.)Available from TIB Hannover: RA 2999(98-018) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman