The dependence of dijet production on the virtuality of the exchanged photon, Q 2, has been studied by measuring dijet cross sections in the range 0≲Q2<2000GeV2 with the ZEUS detector at HERA using an integrated luminosity of 38.6 pb-1. Dijet cross sections were measured for jets with transverse energy EjetT>7.5 and 6.5 GeV and pseudorapidities in the photon-proton centre-of-mass frame in the range −3<ηjet<0 . The variable xobsγ , a measure of the photon momentum entering the hard process, was used to enhance the sensitivity of the measurement to the photon structure. The Q 2 dependence of the ratio of low- to high- xobsγ events was measured. Next-to-leading-order QCD predictions were found to generally underestimate the low- xobsγ contribution relative to that at high xobsγ . Monte Carlo models based on leading-logarithmic parton-showers, using a partonic structure for the photon which falls smoothly with increasing Q 2, provide a qualitative description of the data.
S. Chekanov, M. Derrick, D. Krakauer, J.H. Loizides 1, S. Magill, B. Musgrave, et al. (2004). THE DEPENDENCE OF DIJET PRODUCTION ON PHOTON VIRTUALITY IN EP COLLISIONS AT HERA. EUROPHYSICS LETTERS, C35, 487-500 [10.1140/epjc/s2004-01885-2].
THE DEPENDENCE OF DIJET PRODUCTION ON PHOTON VIRTUALITY IN EP COLLISIONS AT HERA
BASILE, MAURIZIO;CIFARELLI, LUISA;CONTIN, ANDREA;PALMONARI, FEDERICO;RINALDI, LORENZO;SARTORELLI, GABRIELLA;ZICHICHI, ANTONINO;
2004
Abstract
The dependence of dijet production on the virtuality of the exchanged photon, Q 2, has been studied by measuring dijet cross sections in the range 0≲Q2<2000GeV2 with the ZEUS detector at HERA using an integrated luminosity of 38.6 pb-1. Dijet cross sections were measured for jets with transverse energy EjetT>7.5 and 6.5 GeV and pseudorapidities in the photon-proton centre-of-mass frame in the range −3<ηjet<0 . The variable xobsγ , a measure of the photon momentum entering the hard process, was used to enhance the sensitivity of the measurement to the photon structure. The Q 2 dependence of the ratio of low- to high- xobsγ events was measured. Next-to-leading-order QCD predictions were found to generally underestimate the low- xobsγ contribution relative to that at high xobsγ . Monte Carlo models based on leading-logarithmic parton-showers, using a partonic structure for the photon which falls smoothly with increasing Q 2, provide a qualitative description of the data.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
