A detailed next-to-leading order QCD analysis of deeply virtual Compton scattering observables

Abstract

We present a detailed next-to-leading order (NLO) leading twist QCD analysis of deeply virtual Compton scattering (DVCS) observables, for several different input scenarios, in the MS scheme. We discuss the size of the NLO effects and the behavior of the observables in skewedness ζ, momentum transfer, t, and photon virtuality, q 2 = −Q 2 . We present results on the amplitude level for unpolarized and longitudinally polarized lepton probes, and unpolarized and longitudinally polarized proton targets. We make predictions for various asymmetries and for the DVCS cross section and compare with the available data.

GPD phenomenology and DVCS fitting

“…They were followed by numerous dedicated experiments [7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26] during a period of intense theoretical activity which put DVCS under solid control. In particular let us mention the full description of DVCS up to twist-3 [27,28,29,30], including the discussion of QED gauge invariance [31,32,33,34] and target mass and finite momentum transfer corrections [35,36], the computation of higher orders in the perturbative expansion in the strong running coupling [37,38,39,40,41,42,43,44,45,46], and the soft-collinear resummation of DVCS [47,48]. Two closely related processes, Timelike Compton Scattering (TCS) [49,50] and Double Deeply Virtual Compton Scattering (DDVCS) [51,52,…”

PARTONS: PARtonic Tomography Of Nucleon Software

“…During the same period, an intense theoretical activity put DVCS under solid control. In particular we mention the full description of DVCS up to twist-3 [50][51][52][53], the computation of higher orders in the perturbative QCD expansion [54][55][56][57][58][59][60][61][62][63], the softcollinear resummation of DVCS [64,65], the discussion of QED gauge invariance [66][67][68][69][70] and the elucidation of finite-t and target mass corrections [71,72]. Variety of those existing theoretical improvements, usually developed within the model/framework preferred by the corresponding authors, also justify the need for a common framework enabling systematic comparisons.…”

Deeply virtual compton scattering in color dipole formalism

“…This prediction is dependent on the Generalised Parton Distributions (GPD), which have been parameterized in Ref. [17] and applied to describe the recent DVCS data [15,16]. The second theoretical approach [4,5] is given by the color dipole approach, where the basic building blocks are the photon wavefunctions and the dipole cross section.…”

“…The non-forward kinematics is encoded by the wavefunctions whereas the off- diagonal effects can be built-in in the parameterizations for the dipole-target cross section. The DVCS cross section has been calculated at NLO in perturbative QCD by Freund and McDermott [15,16] using two different GPD parameterizations [17]. The MRST2001 and CTEQ6 parameterizations of the PDFs are used in the DGLAP region and polynomial form is used in the ERBL region, ensuring a smooth continuation between the two regions.…”