Deeply virtual Compton scattering and its beam charge asymmetry in e(+/-)p collisions at HERA
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A measurement of elastic deeply virtual Compton scattering gamma*p -- GT gamma p using e(+) p and e(-) p collision data recorded with the HI detector at HERA is presented. The analysed data sample corresponds to an integrated luminosity of 306 pb(-1), almost equally shared between both beam charges. The cross section is measured as a function of the virtuality Q(2) of the exchanged photon and the centre-of-mass energy W of the gamma*p system in the kinematic domain 6.5 LT Q(2) LT 80 GeV2, 30 LT W LT 140 GeV and |t| LT 1 GeV2, where t denotes the squared momentum transfer at the proton vertex. The cross section is determined differentially in t for different Q(2) and W values and exponential t-slope parameters are derived. Using e(+) p and e(-) p data samples, a beam charge asymmetry is extracted for the first time in the low Biorken x kinematic domain. The observed asymmetry is attributed to the interference between Bethe-Heitler and deeply virtual Compton scattering processes. Experim...ental results are discussed in the context of two different models, one based on generalised parton distributions and one based on the dipole approach. (C) 2009 Elsevier B.V. All rights reserved.
Izvor:Physics Letters B, 2009, 681, 5, 391-399
- World Laboratory Bjorn Wiik Research Project, European Social Fund, National Resources, UK Science and Technology Facilities Council, UK Particle Physics and Astronomy Research Council, FNRS-FWO-Vlaanderen, IISN-IIKW, IWT, Interuniversity Attraction Poles Programme, Belgian Science Policy, Ministry of Science and Higher Education [PBS/DESY/70/2006], Bundesministerium fur Bildung und Forschung, FRG [05H09GUF, 05H09VHC, 05H09VHF, 05H16PEA], VEGA SR [2/7062/27], Swedish Natural Science Research Council, CONACYT [48778-F], Russian Foundation for Basic Research (RFBR) [1329.2008.2], Deutsche Forschungsgemeinschaft, Ministry of Education of the Czech Republic [LC527, INGO-1P0SLA259, MSM0021620859], Swiss National Science Foundation