Deeply virtual Compton scattering via color dipoles: Nonperturbative effects

Kopeliovich, B. Z.; Schmidt, Iván; Siddikov, Marat

doi:10.1103/physrevd.79.034019

Cited by 11 publications

(13 citation statements)

References 50 publications

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“…At high energies in the small angle approximation, Á= ffiffi ffi s p ( 1, the quark separation and fractional momenta are preserved, so A d ð 1 ;r 1 ; 2 ;r 2 ;Q 2 ;ÁÞ % ð 1 À 2 Þðr 1 Àr 2 Þð þ iÞ=mf N " qq ðr;Á;;sÞ; (4) where 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 [25,[47][48][49],…”

Section: Diffractive Pion Production On a Protonmentioning

confidence: 99%

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Diffractive neutrino production of pions on nuclei: Adler relation within the color-dipole description

2012

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Effects of coherence in neutrino production of pions off nuclei are studied employing the color-dipole representation and path integral technique. If the nucleus remains intact, the process is controlled by the interplay of two length scales. One is related to the pion mass and is quite long (at low Q 2 ), while the other, associated with heavy axial-vector states, is much shorter. The Adler relation is found to be broken at all energies, but especially strongly at * 10 GeV, where the cross section is suppressed by a factor $A À1=3 . On the contrary, in a process where the recoil nucleus breaks up into fragments, the Adler relation turns out to be strongly broken at low energies, where the cross section is enhanced by a factor $A 1=3 , but has a reasonable accuracy at higher energies, where all the coherence length scales become long.

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Section: Diffractive Pion Production On a Protonmentioning

confidence: 99%

“…[25][26][27][28][29][30][31]) giving a reasonable description of the total and differential cross sections. Also, the color-dipole model has been applied to the description of the neutrino physics in [32][33][34][35][36][37][38][39].…”

Section: Introductionmentioning

confidence: 99%

Diffractive neutrino production of pions on nuclei: Adler relation within the color-dipole description

2012

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“…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],…”

Section: Diffractive Production Of Pionsmentioning

confidence: 99%

“…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).…”

Section: Introductionmentioning

confidence: 99%

“…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.…”

Section: Introductionmentioning

confidence: 99%

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Neutrino production of single pions: Dipole description

2011

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The light-cone distribution amplitudes for the axial current are derived within the instanton vacuum model (IVM), which incorporates nonperturbative effects including spontaneous chiral symmetry breaking. This allows to extend applicability of the dipole approach, usually used in the perturbative domain, down to Q 2 → 0, where partially conserved axial current (PCAC) imposes a relation between the neutrino-production cross section and the one induced by pions. A dramatic breakdown of the Adler relation (AR) for diffractive neutrino-production of pions, caused by absorptive corrections, was revealed recently in [1]. Indeed, comparing with the cross section predicted by the dipole phenomenology at Q 2 → 0 on a proton target we confirmed the sizable deviation from the value given by the AR, as was estimated in [1] within a simplified two-channel model. The dipole approach also confirms that in the black-disc limit, where the absorptive corrections maximize, the diffractive cross section ceases, on the contrary to the expectation based on PCAC.

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Deeply virtual Compton scattering at small xB and the access to the GPD H

2010

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We give a partonic interpretation for the deeply virtual Compton scattering (DVCS) measurements of the H1 and ZEUS Collaborations in the small-x B region in terms of generalized parton distributions. Thereby we have a closer look at the skewness effect, parameterization of the t-dependence, revealing the chromomagnetic pomeron, and at a model-dependent access to the anomalous gravitomagnetic moment of nucleon. We also quantify the reparameterization of generalized parton distributions resulting from the inclusion of radiative corrections up to next-to-next-to-leading order. Beyond the leading order approximation, our findings are compatible with a 'holographic' principle that would arise from a (broken) SO(2,1) symmetry. Utilizing our leading-order findings, we also perform a first model-dependent "dispersion relation" fit of HERMES and JLAB DVCS measurements. From that we extract the generalized parton distribution H on its cross-over line and predict the beam charge-spin asymmetry, measurable at COMPASS. This is nothing but the RDDA model in the limit b → ∞; practically, a large value b ≫ 1 is sufficient. This ansatz implies that the skewness function is set r(η/x) = 1 for all x. With such an initial condition, evolution, starting at a rather low input scale, will rapidly lead to an increase of the r-ratio. Thus, this GPD model fails to describe data, too. We will not go into details here, 7 Usage of term "dual" was motivated by the fact that in dual models [98] the s-channel amplitude is described by the t-channel exchanges. We add that this feature is more general and arises from crossing and the Sommerfeld-Watson transform of the t-channel SO(3) partial wave expansion. In Regge theory/phenomenology the resummation of t-channel exchanges is encoded in the Regge trajectory.

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Deeply virtual Compton scattering via color dipoles: Nonperturbative effects

Cited by 11 publications

References 50 publications

Diffractive neutrino production of pions on nuclei: Adler relation within the color-dipole description

Diffractive neutrino production of pions on nuclei: Adler relation within the color-dipole description

Neutrino production of single pions: Dipole description

Deeply virtual Compton scattering at small xB and the access to the GPD H

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