Observation of isolated high-E-T photons in photoproduction at HERA

Events containing an isolated prompt photon with high transverse energy, together with a balancing jet, have been observed for the first time in photoproduction at HERA. The data were taken with the ZEUS detector, in a gamma p centre of mass energy range 120-250 GeV. The fraction of the incoming photon energy participating in the production of the prompt photon and the jet, x(gamma), shows a strong peak near unity, consistent with LO QCD Monte Carlo predictions. In the transverse energy and pseudorapidity range 5 less than or equal to E-T(gamma) < 10 GeV, -0.7 less than or equal to eta(gamma) < 0.8, E-T(jet) greater than or equal to 5 GeV, and -1.5 less than or equal to eta(jet) less than or equal to 1.8, with x(gamma)(OBS) > 0.8, the measured cross section is 15.3 +/- 3.8 +/- 1.8 ph, in good agreement with a recent NLO calculation. (C) 1997 Elsevier Science B.V. RI Bashkirov, Vladimir/A-4818-2008; De Pasquale, Salvatore/B-9165-2008; Lancaster, Mark/C-1693-2008; Doyle, Anthony/C-5889-2009; Gladilin, Leonid/B-5226-2011; Golubkov, Yury/E-1643-2012

Events containing an isolated prompt photon with high transverse energy, together with a balancing jet, have been observed for the first time in photoproduction at HERA. The data were taken with the ZEUS detector, in a gamma p centre of mass energy range 120-250 GeV. The fraction of the incoming photon energy participating in the production of the prompt photon and the jet, x(gamma), shows a strong peak near unity, consistent with LO QCD Monte Carlo predictions. In the transverse energy and pseudorapidity range 5 less than or equal to E-T(gamma) < 10 GeV, -0.7 less than or equal to eta(gamma) < 0.8, E-T(jet) greater than or equal to 5 GeV, and -1.5 less than or equal to eta(jet) less than or equal to 1.8, with x(gamma)(OBS) > 0.8, the measured cross section is 15.3 +/- 3.8 +/- 1.8 ph, in good agreement with a recent NLO calculation. (C) 1997 Elsevier Science B.V.