Seminars and Journal Clubs
Study of Deeply Virtual Compton Scattering at HERA II
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Europe/Brussels
CP3 seminar room
CP3 seminar room
Description
The high beam energies of the HERA electron-proton collider has enabled the H1 Collaboration to study the proton structure, through the measurement of Deep Inelastic Scattering (DIS) events e p -> e X, in a wide range in Q2 and Bjorken variable x_Bj, respectively the virtuality of the exchanged photon and the proton momentum fraction carried by the struck quark. The high values of Q2 allowed the applicability of perturbative QCD to extract the parton distribution functions (pdf) of the proton. The observation in the 90's of so-called inclusive diffractive events e p -> e p X in the DIS regime, for which the elastically scattered proton and the hadronic final state X are separated by a large gap in pseudo-rapidity without hadronic activity, has allowed to give a QCD description of the color singlet exchange occuring between the proton and the virtual photon in this type of reactions. The study of exclusive diffractive events, in which the hadronic final state X reduces to a unique particle, has been these last years a center of interests because of the new insight they can give into the proton structure, through the extraction of the so-called Generalized Parton Distributions (GPD). Among these events, Deeply Virtual Compton Scattering (DVCS) process e p -> e p gamma has a clear experimental signature, a precise theoretical description in the framework of QCD and a simple interpretation in terms of GPD.
I will present the study achieved in my PhD of measurements of the DVCS cross section sigma(gamma* p-> gamma p) as a function of the photon virtuality Q2, the gamma* p cms energy W and the momentum transfer squared at the proton vertex, t, enabling one to test precisely the QCD description of the DVCS process, to constrain parametrizations of GPD and to get a more complete and unified picture of the proton structure. The study presented covers the kinematic range 6.5 < Q2 < 80 GeV2, 30 < W < 140 GeV and |t| < 1 GeV2, is based on the data collected by the H1 experiment during the years 2004 and 2005 and corresponds to an integrated luminosity of 134.8 pb-1.