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A. E. Dorokhov

Publications and source records attributed to A. E. Dorokhov.

At least 55 records · Page 3Linked to original sources
arXiv2005

Singlet VA \tilde V correlator within the instanton vacuum model

The correlator of singlet axial-vector and vector currents in the external electromagnetic field is studied within the instanton liquid model of QCD vacuum. In the chiral limit we calculate the longitudinal w_L^0 and transversal w_T^0 with respect to axial-vector index invariant amplitudes at arbitrary momentum transfer q. It is demonstrated how the anomalous longitudinal part of the correlator is renormalized at low momenta due to the presence of the U_A(1) anomaly.

hep-ph↗
arXiv2005

VA\tilde V correlator within the instanton vacuum model

The correlator of vector and nonsinglet axial-vector currents in the external electromagnetic field is calculated within the instanton liquid model of QCD vacuum. In general the correlator has two Lorentz structures: longitudinal w_L and transversal w_T with respect to axial-vector index. Within the instanton model the saturation of the anomalous w_L structure is demonstrated. It is known that in the chiral limit the transversal structure w_T is free from perturbative corrections. In this limit within the instanton model we calculate the transversal invariant function w_T at arbitrary momentum transfer, q, and show the absence of power corrections to this structure at large q^2. Instead there arise the exponential corrections to w_T at large q^2 reflecting nonlocal properties of QCD vacuum. The slope of w_T at zero virtuality, the QCD vacuum magnetic susceptibility of the quark condensate and its momentum dependence are estimated.

hep-ph↗
arXiv2004

Vector and Axial-Vector correlators in a instanton-like quark model

The behavior of the vector Adler function at spacelike momenta is studied in the framework of a covariant chiral quark model with instanton-like quark-quark interaction. The model reproduces the Adler function and $V-A$ correlator extracted from the ALEPH and OPAL data on hadronic $τ$ lepton decays, transformed into the Euclidean domain via dispersion relations. The leading order contribution from hadronic part of the photon vacuum polarization to the anomalous magnetic moment of the muon, $a_μ^{\mathrm{hvp}(1)} $, is estimated.

hep-ph↗
arXiv2004

Vector and axial-vector current correlators within the instanton model of QCD vacuum

The pion electric polarizability, α^E_π^\pm, the leading order hadronic contribution to the muon anomalous magnetic moment, $a_μ^{hvp 1} $, and the ratio of the difference to the sum of vector and axial-vector correlators, (V-A)/(V+A), are found within the instanton model of QCD vacuum. The results are compared with phenomenological estimates of these quantities following from the ALEPH and OPAL data on vector and axial-vector spectral densities.

hep-ph↗
arXiv2004

QCD instantons in high energy diffractive scattering: Instanton model of Pomeron

The role of the QCD vacuum effects in high energy diffractive quark-quark and quark-antiquark scattering is studied with the Instanton Liquid Model. The special attention is given to the problem of formation of the soft Pomeron. We show that in the leading approximation in instanton density the $C-$odd instanton contribution to the diffractive amplitude is suppressed as $1/s$ compared to the $C-$even one.

hep-ph↗
arXiv2004

Study of instanton effects in electromagnetic quark form factor at high energy

The detailed analysis of nonperturbative contributions to the electromagnetic quark form factor is performed within the framework of the instanton liquid model (ILM) of the QCD vacuum. The method of the path-ordered Wilson exponentials is applied to evaluate explicitly the instanton corrections. By using the Gaussian interpolation of the constrained instanton solution, it is shown that the instantons yield the logarithmic corrections to the amplitudes in high energy limit which are exponentiated in small instanton density parameter.

hep-ph↗
arXiv2004

Effects of QCD Vacuum and Stability of H Dihyperon

Within the composite quark model taking into account the interaction of quarks in the bag with vacuum fields of QCD the masses of H (I=0,S=-2,J=0,1^C) and H* (I=0,S=-2,J=1,1^C) dihyperons are estimated: M_H=2.16 GeV, M_H*=2.34 GeV. It is shown that the leading effect giving a stable with respect to strong decays H dihyperon is the instanton interaction forming diquarks: q^2(J=0,C=3), q^2(J=0,C=6). With the approach developed the contribution of QCD hyperfine interaction is suppressed, and instanton induced three-particle forces in multiquark hadrons (q^3(J=1/2,C=8) - channel) are rather small.

hep-ph↗
arXiv2004

Adler function and hadronic contribution to the muon g-2 in a nonlocal chiral quark model

The behavior of the vector Adler function at spacelike momenta is studied in the framework of a covariant chiral quark model with instanton-like quark-quark interaction. This function describes the transition between the high energy asymptotically free region of almost massless current quarks to the low energy hadronized regime with massive constituent quarks. The model reproduces the Adler function and V-A correlator extracted from the ALEPH and OPAL data on hadronic τlepton decays, transformed into the Euclidean domain via dispersion relations. The leading order contribution from hadronic part of the photon vacuum polarization to the anomalous magnetic moment of the muon, a_μ^{hvp,1}, is estimated.

hep-ph↗
arXiv2004

Instanton effects in quark form factor and quark-quark scattering at high energy

The nonperturbative effects in the high-energy processes involving strongly interacting particles are studied within the instanton liquid model of the QCD vacuum (ILM) by using the Wilson integral framework. The detailed analysis of nonperturbative contributions to the electromagnetic quark form factor is presented considering the structure of the instanton induced effects in the evolution equation describing the high energy behaviour of the form factor. It is shown that the instantons yield in high energy limit the logarithmic corrections to the amplitudes which are exponentiated in small instanton density parameter. By using the Gaussian interpolation of the constrained instanton solution, we show that the all-order multi-instanton contribution is well approximated by the weak field limit result. The role of the instantons in high energy diffractive quark-quark scattering, in particular, in formation of the soft Pomeron, is also considered. We show that within the ILM the C-odd diffractive amplitude is suppressed as 1/s compared to the C-even one. The further applications of the developed approach in studying the nonperturbative effects in high energy hadronic processes are briefly discussed.

hep-ph↗
arXiv2004

QCD vacuum topological susceptibility in a non-local chiral quark model

The topological susceptibility of QCD vacuum is studied in the framework of a covariant chiral quark model with non-local quark-quark interaction. The relation of the first moment of topological susceptibility χ'(0) and the 'spin crisis' problem is briefly discussed. It is shown, in particular, that one always gets the inequality χ'(0)>χ'_{OZI}.

hep-ph↗
arXiv2004

Pion radii in nonlocal chiral quark model

The electromagnetic radius of the charged pion and the transition radius of the neutral pion are calculated in the framework of the nonlocal chiral quark model. It is shown in this model that the contributions of vector mesons to the pion radii are noticeably suppressed in comparison with a similar contribution in the local Nambu--Jona-Lasinio model. The form-factor for the process gamma*pi+pi- is calculated for the -1 GeV^2<q^2<1.6 GeV^2. Our results are in satisfactory agreement with experimental data.

hep-ph↗
arXiv2003

Vector and axial-vector correlators in a nonlocal chiral quark model

The behavior of nonperturbative parts of the isovector-vector and isovector and isosinglet axial-vector correlators at Euclidean momenta is studied in the framework of a covariant chiral quark model with nonlocal quark-quark interactions. The gauge covariance is ensured with the help of the P-exponents, with the corresponding modification of the quark-current interaction vertices taken into account. The low- and high-momentum behavior of the correlators is compared with the chiral perturbation theory and with the QCD operator product expansion, respectively. The V-A combination of the correlators obtained in the model reproduces quantitatively the ALEPH data on hadronic τdecays, transformed into the Euclidean domain via dispersion relations. The predictions for the electromagnetic π^\pm - π^0 mass difference and for the pion electric polarizability are also in agreement with the experimental values. The topological susceptibility of the vacuum is evaluated as a function of the momentum, and its first moment is predicted to be χ'(0)\approx (50 MeV)^2. In addition, the fulfillment of the Crewther theorem is demonstrated.

hep-ph↗
arXiv2003

Instanton effects in high energy processes

Manifestation of the nonperturbative effects in hadron processes at high energy is discussed within the instanton liquid model. Their role in high energy diffractive quark-quark scattering, quark form factor and hard exclusive processes with pion participation is illuminated.

hep-ph↗
arXiv2002

Pion distribution amplitudes within the instanton model of QCD vacuum

Pion transition form factor for the process $γ*γ*\to π^0$ at space-like values of photon momenta is calculated within the effective quark-meson model with the interaction induced by instanton exchange. The leading and next-to-leading order power asymptotics of the form factor and the relation between the light-cone pion distribution amplitudes of twists 2 and 4 and the dynamically generated quark mass are found.

hep-ph↗
arXiv2002

Instanton model of light hadrons: from low to high energies

Instanton liquid model being effective model of the QCD vacuum describes well the hadrons at low as well at intermediate energies. Thus, contact with perturbative QCD results is possible providing the unique information about the quark-gluon distribution functions in the QCD vacuum and hadrons at low energy normalization point. As an illustrative example we consider the pion transition form factor for the process $γ^*γ^*\to π^0$ at space-like values of photon momenta. The leading and next-to-leading order power asymptotics of the form factor and the relation between the light-cone pion distribution amplitudes of twists 2 and 4 and the dynamically generated quark mass are found.

hep-ph↗
arXiv2002

Pion transition form factor: interplay of hard and soft limits

The behaviour of the pion transition form factor for the process $γ^\starγ\to π^0$ and $γ^\starγ^\star\to π^0$ at space-like values of photon momenta is estimated within the nonlocal covariant quark-meson model. The nonlocal contributions are important to install the axial anomaly at zero photon virtualities and give the contributions to the twist-4 power correction to the form factor at large virtualities. The leading and next-to-leading order power asymptotics of the form factor and the relation between the light-cone pion distribution amplitudes and the dynamically generated quark mass function are found.

hep-ph↗
arXiv2002

Transition form factors and light-cone distribution amplitudes of pseudoscalar mesons in the chiral quark model

It is shown that a chiral quark model of the Nambu--Jona-Lasinio type can be used to describe "soft"-momenta parts of the amplitudes with large momentum transfer. As a sample, the processes γ^* --> γ(π,η,η') where one of the photons, γ^*, has large space-like virtuality is investigated. The γ^* --> γ(π,η,η')$ transition form factors are calculated for a wide region of transferred momenta. The results are consistent with the calculations performed in the instanton-induced chiral quark model and agree with experimental data. The distribution amplitudes of pseudoscalar mesons are derived.

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