DVCS via color dipoles: Nonperturbative effects

Abstract

We study the DVCS amplitude within the color dipole approach. The light-cone wave function of a real photon is evaluated in the instanton vacuum model. Our parameter free calculations are able to describe H1 data, both the absolute values and the t-dependences, at medium-high values of Q 2 . The Q 2 dependence is found to be sensitive to the choice of the phenomenological cross section fitted to DIS data.

Neutrino production of single pions: Dipole description

“…where ǫ is the ratio of the real to imaginary parts, and for the imaginary part of the elastic dipole amplitude we employ the model developed in [11,[57][58][59],…”

“…After the dipole is formed, it scatters in the field of the target and then fluctuates back to the final hadron [7]. Recently the color dipole approach has been successfully applied to the description of different reactions with vector currents (see [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] and references therein).…”

“…Similarly, in order to test the mysterious relation between the contribution of heavy hadronic fluctuations and pion, one should switch to the dipole representation and employ models for the distribution amplitudes (DA) of the axial current which have built-in chiral symmetry. Recently, we used the DA of the vector current calculated in the IVM for the evaluation of several processes [11][12][13][14]. In this paper we apply the IVM to construct the DAs for the axial current and pion and use them to calculate the neutrino-production cross sections.…”

Real Compton scattering via color dipoles

“…We use the s-dependent dipole cross section proposed in [42], which saturates at large separations in analogy to the x-dependent one proposed in [43]. Correspondingly, for the elastic dipole amplitude we employ the model developed in [34,44,45,46],…”

“…While pQCD predicts the dipole amplitude only for small-size dipoles, several successful phenomenological parameterizations for the large-size dipoles are known. Relying on the photon wave function evaluated in the instanton vacuum model [33], which is valid for any Q 2 , one can extend the applicability of the model to the case of the processes with real photons [34]. In this paper we are going to consider the real photoabsorption, γ + p → X, and the RCS.…”