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K. N. Zyablyuk

Publications and source records attributed to K. N. Zyablyuk.

15 recordsLinked to original sources
arXiv2005

Pion structure functions at 2 loops: final state interaction with spectator

Pion structure functions are considered in the framework of QCD sum rules at the next to leading order. The 2-loop diargam, representing the gluon exchange between the struck quark and spectator, is calculated for space-like pion momentum p^2<0. After Borel transformation we obtain a leading twist correction to the pion structure function, which does not violate Bjorken scaling. Partial results can be used in the calculation of complete set of alpha_s corrections to the pion structure functions, which may serve as an intitial condition in the evolution equation. Probabilistic interpretation of the structure functions is discussed.

hep-ph↗
arXiv2004

V-A sum rules with D=10 operators

The difference of vector and axial-vector charged current correlators is analyzed by means of QCD sum rules. The contribution of 10-dimensional 4-quark condensates is calculated and its value is estimated within the framework of factorization hypothesis. It is compared to the result, obtained from operator fit of Borel sum rules in the complex q^2-plane, calculated from experimental data on hadronic tau-decays. This fit gives accurate values of the light quark condensate and quark-gluon mixed condensate. The size of the high-order operators and the convergence of operator series are discussed.

hep-ph↗
arXiv2004

Production of light antinuclei in heavy ion collisions

The antideuteron and antihelium-3 production rates at high-energy heavy ion collisions are calculated in the framework of fusion mechanism. It is supposed, that anti-p,n,d,^3He participating in the fusion are moving in the mean field of other fireball constituents. It is demonstrated that at high energies, where many pions are present in the fireball, the number of produced anti-d and ^3He is determined by the balance between created and desintegrated (mainly in collisions with pions) anti-d and ^3He. The explicit formulae for coalescence parameters are presented and compared with the data.

nucl-th↗
arXiv2003

Formation of antideuterons in heavy ion collisions

The antideuteron production rate at high-energy heavy ions collisions is calculated basing on the concept of anti-d formation by antinucleons which move in the mean field of the fireball constituents (mainly pions). The explicit formula is presented for the coalescence parameter B_2 in terms of deuteron binding energy and fireball volume.

hep-ph↗
arXiv2002

Gluon condensate in charmonium sum rules with 3-loop corrections

Charmonium sum rules are analyzed with the primary goal to obtain the restrictions on the value of dimension 4 gluon condensate. The moments M_n(Q^2) of the polarization operator of vector charm currents are calculated and compared with experimental data. The 3-loop (alpha_s^2) perturbative corrections, the gluon condensate contribution with alpha_s corrections and dimension 6 operator G^3 contribution are accounted. It is shown that the sum rules for the moments do not work at Q^2=0, where the perturbation series diverges and G^3 contribution is large. The domain in the plane (n, Q^2), where the sum rules are legitimate, is found. Strong correlation of the values of gluon condensate and MS-bar charm quark mass quark is determined. The absolute limits are found to be for gluon condensate <(alpha_s/pi)G^2>=0.009+-0.007 GeV^4 and for charm quark mass m(m)=1.275+-0.015 GeV in MS-bar scheme.

hep-ph↗
arXiv2001

QCD sum rule analysis of V and A current correlators from tau-decay data

2-point correlators of vector and axial currents, obtained from tau-decay data, are studied within the framework of perturbative QCD and Operator Product Expansion. Various sum rules, obtained from Borel transformation of the correlators in complex plane, are used to separate the contributions of different operators from each other. The analysis confirms the Q^2-dependence of the correlators in the space-like region, predicted by QCD+OPE. However the operator values are found to be in certain disagreement with the estimations, obtained from other data.

hep-ph↗
arXiv2001

The check of QCD based on the tau-decay data analysis in the complex q^2-plane

The thorough analysis of the ALEPH data on hadronic tau-decay is performed in the framework of QCD. The perturbative calculations are performed in 3 and 4-loop approximations. The terms of the operator product expansion (OPE) are accounted up to dimension D=8. The value of the QCD coupling constant alpha_s(m_tau^2)=0.355 pm 0.025 was found from hadronic branching ratio R_tau. The V+A and V spectral function are analyzed using analytical properties of polarization operators in the whole complex q^2-plane. Borel sum rules in the complex q^2 plane along the rays, starting from the origin, are used. It was demonstrated that QCD with OPE terms is in agreement with the data for the coupling constant close to the lower error edge alpha_s(m_tau^2)=0.330. The restriction on the value of the gluonic condensate was found <(alpha_s/pi)G^2>=0.006 pm 0.012 GeV^2. The analytical perturbative QCD was compared with the data. It is demonstrated to be in strong contradiction with experiment. The restrictions on the renormalon contribution were found. The instanton contributions to the polarization operator are analyzed in various sum rules. In Borel transformation they appear to be small, but not in spectral moments sum rules.

hep-ph↗
arXiv2000

The V-A sum rules and the Operator Product Expansion in complex q^2-plane from tau-decay data

The operator product expansion (OPE) for the difference of vector and axial current correlators is analyzed for complex values of momentum q^2. The vector and axial spectral functions, taken from hadronic tau-decay data, are treated with the help of Borel, Gaussian and spectral moments sum rules. The range of applicability, advantages and disadvantages of each type are discussed. The general features of OPE are confirmed by the data. The vacuum expectation values of dimension 6 and 8 operators are found to be O_6=-(6.8\pm 2.1)*10^{-3} GeV^6, O_8=(7\pm 4)*10^{-3} GeV^8.

hep-ph↗
arXiv1996

Vanishing of Cosmological Constant in Dual Supergravity

The vacuun configuration of dual supergravity in ten dimensions with one-loop fivebrane corrections is analyzed. It is shown that the compactification of this theory with rather general conditions to six-dimensional space leads to zero value of cosmological constant.

hep-th↗
arXiv1996

Fivebrane Lagrangian with Loop Corrections in Field-Theory Limit

Equations of motion and the lagrangian are derived explicitely for Dual D=10, N=1 Supergravity considered as a field theory limit of a Fivebrane. It is used the mass-shell solution of Heterotic String Bianchi Identites obtained in the 2-dimensional $σ$-model two-loop approximation and in the tree-level Heterotic String approximation. As a result the Dual Supergravity lagrangian is derived in the one-loop Five-Brane approximation and in the lowest 6-dimensional $σ$-model approximaton.

hep-th↗
arXiv1996

New Constraints from Electric Dipole Moments on Parameters of the Supersymmetric SO(10) Model

We calculate the chromoelectric dipole moment (CEDM) of d- and s-quark in the supersymmetric SO(10) model. CEDM is more efficient than quark electric dipole moment (EDM), in inducing the neutron EDM. New, strict constraints on parameters of the supersymmetric SO(10) model follow in this way from the neutron dipole moment experiments. As strict bounds are derived from the upper limits on the dipole moment of odd isotope of mercury.

hep-ph↗
arXiv1996

Universal scheme of minimal reduction of usual and dual N=1,D=10 supergravity to the Minkowsky space

The reduction from N=1, D=10 to N=4, D=4 supergravity with the Yang-Mills matter is considered. For this purpose a set of constraints is imposed in order to exclude six additional abelian matter multiplets and conserve the supersymmetry. We consider both the cases of usual and dual N=1, D=10 supergravity using the superspace approach. Also the effective potential of the deriving theory is written.

hep-th↗
arXiv1995

Duality in N=1, D=10 Superspace and Supergravity with Tree Level Superstring Corrections

The equations of motion (e.m.'s) of the N=1, D=10 anomaly free supergravity, obtained in the framework of the superspace approach, are analyzed. The formal equivalence of the usual and dual supergravities is discussed at the level of e.m.'s. The great simplicity of the dual formulation is established. The possibillity of the lagrangian formulation of the dual supergravity is pointed out. The bosonic part of the lagrangian is constructed including anomaly compensating superstring corrections.

hep-th↗
arXiv1994

Interaction of Dual N=1, D=10 Supergravity with Yang-Mills Matter Multiplet

The lagrangian of the N=1, D=10 dual supergravity interacting with the Yang-Mills matter multiplet is constructed starting immediately from the equations of motion obtained from the Bianchi Identities in the superspace approach. The difference is established in comparison with the Gates-Nishino lagrangian at the fourth order level in fermionic fields.

hep-th↗