N -> Delta DVCS, exclusive DIS processes and skewed quark distributions in large N_c limit

Abstract

We evaluate the amplitude of Bethe-Heitler process: \gamma^* p -> \gamma \Delta^+ -electron bremsstrahlung of photon accompanied by the excitation of \Delta$isobar.Weshowthatthisbackgroundissuppressedatsmallmomentumtransfersquaredttoaprotonrelativetothatfor{\gamma }^{\ast }p->\gamma pand{\gamma }^{\ast }p\to ->{\Delta }^{+}-DVCSprocesses.Fromexperimentalpointofview,thismeansthatN->NandN->\Delta skewedquarkdistributions(SQ{D}^{\prime }s)mightbemeasurableatsmallmomentumtransfer.SeveralimplicationsandapplicationsoftheQCDfactorizationtheoremfortheprocesses{\gamma }_L^{\ast }+p->h_f+h_{s}arediscussedwhere{h}_f-theparticleproducedalongphotonmomentum$\vec q$ maybe either a meson or a baryon. We discuss also t dependence of DVCS and exclusive meson production as the practical criteria to distinguish between soft and hard regime. Basing on the large-N_c picture of the nucleon as a soliton of the effective chiral Lagrangian we derive relations between N -> N and N ->\Delta SQD's which can be used to estimate amplitude of N -> \Delta DVCS .

Comments: 8 pages, latex. Contribution to the Workshop " Jefferson Lab Physics and Instrumentation with 6-12 GeV Beams", Newport News, VA, June 15-18, 1998