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F. C. Khanna

Publications and source records attributed to F. C. Khanna.

101 records · Page 6Linked to original sources
arXiv1996

A test of the instanton vacuum chiral quark model with axial anomaly low-energy theorems

The QCD + QED axial anomaly low-energy theorems are applied to estimate the accuracy of an instanton vacuum - based chiral quark model. The low-energy theorems give an exact relation between the matrix elements of the gluon and photon parts of the QCD + QED axial anomaly operator equation. The matrix elements between vacuum and two photon states and between vacuum and two gluon states are calculated for arbitrary N_f. It is shown that this model does satisfy the low-energy theorems with an accuracy of $\sim 17%$. We estimate also the contribution of the nonperturbative conversion of gluons into photons to the decay $η' \rightarrow 2 γ$ and compare with experimental data.

hep-ph↗
arXiv1996

Chiral-Odd Structure Function h_1^D(x) and Tensor Charge of the Deuteron

The chiral-odd structure function h_{1}^D(x) and the tensor charge of the deuteron are studied within the Bethe-Salpeter formalism for the deuteron amplitude. Utilizing a simple model for the nucleon structure function, h_1^N, h_1^D(x) is calculated and the nuclear effects are analyzed.

hep-ph↗
arXiv1996

Deep inelastic scattering on the deuteron in the Bethe-Salpeter formalism II: Realistic $NN$-interaction

We present a systematic study of the leading twist structure functions of the deuteron, F_2^D, b_{1,2}^D and g_1^D in a fully relativistic approach. Our study is based on a realistic Bethe-Salpeter amplitude for the deuteron, which is obtained as a solution to the homogeneous Bethe-Salpeter equation with a realistic NN kernel. Particular effort is made to connect the structure functions to the densities of the appropriate charges and currents. This allows for a systematic comparison between the relativistic and nonrelativistic calculations, by analysing the same densities in both approaches. Thus, the sources of the relativistic effects in the structure functions are understood and clearly distinguished from variations caused by the differences in the model parameters. We present both the formalism and extensive numerical calculations for all steps of our analysis. We find that the nonrelativistic and relativistic calculations are qualitatively very much alike. However, three main features systematically distinguish a consistent relativistic approach from the nonrelativistic one: (i) the binding effects are larger, (ii) the effect of Fermi motion at high $x$ is stronger and (iii) the relativistic description of the structure functions b_{1,2}^D is fully consistent, unlike the nonrelativistic approach, which is internally inconsistent and violates the fundamental sum rules.

hep-ph↗
arXiv1996

The deformation of the interacting nucleon in the Skyrme model

Changes in the nucleon shape are investigated by letting the nucleon deform under the strong interactions with another nucleon. The parameters of the axial deformations are obtained by minimizing the static energy of the two nucleon system at each internucleon distance $ R $. It is shown that the intrinsic quadrupole moment of the interacting proton, $Q_{p}$, is about $0.02 fm^2$ at distances near $R \sim 1.25 $ fm.

nucl-th↗
arXiv1996

The axial anomaly and the conversion of gluons into photons

The axial anomaly in the divergence of the singlet axial current in QCD $+$ QED leads to low-energy theorems for the matrix element of this operator equation over vacuum and two--photon states and for the matrix element over vacuum and two--gluon states. The solution of these theorems is related only to the nonperturbative phenomena. These matrix elements are calculated in instanton vacuum generated N-JL type quark model for arbitrary $N_f .$ It is shown that this model does satisfy the low-energy theorems.

hep-ph↗
arXiv1996

Bethe-Salpeter Amplitudes and Static Properties of the Deuteron

Extended calculations of the deuteron's static properties, based on the numerical solution of the Bethe-Salpeter equation, are presented. A formalism is developed, which provides a comparative analysis of the covariant amplitudes in various representations and nonrelativistic wave functions. The magnetic and quadrupole moments of the deuteron are calculated in the Bethe-Salpeter formalism and the role of relativistic corrections is discussed.

nucl-th↗
arXiv1995

The Spectrum and Confinement for the Bethe-Salpeter Equation

The problem of calculating of the mass spectrum of the two-body Bethe-Salpeter equation is studied with no reduction to the three-dimensional ("quasipotential") equation. The method to find the ground state and excited states for a channel with any quantum numbers is presented. The problem of the confining interaction for the Bethe-Salpeter equation is discussed from the point of view of formal properties of the bound state spectrum, but with only an inspiration from the QCD. We study the kernel that is non-vanishing at large Euclidian intervals, $R_E\to \infty$, which is constructed as a special limiting case of a sum of the covariant one-boson-exchange kernels. When the usual attractive interaction is added, it is found that this kernel is similar in its effect to the non-relativistic potential in coordinate space, $V(r)$, with $V(r\to \infty) \to V_{\infty}$. The positive real constant $V_{\infty}$ gives the scale that define the limit of bound state spectrum compared to the sum of the constituent masses, $M < 2m + V_{\infty}$. At the same time the self-energy corrections remove the singularities from the propagators of the constituents, i.e. constituents do not propagate as free particles. Combination of these features of the solutions allows an interpretation of this type of interaction as a confining one. The illustrative calculations are presented for a model of massive scalar particles with scalar interaction, i.e. the "massive Wick model".

hep-ph↗
arXiv1994

On the Off-Mass-Shell Deformation of the Nucleon Structure Function

The off-mass-shell behavior of the nucleon structure function, $F_2^N$, is studied within an approach motivated by the Sullivan model. Deep inelastic scattering on the nucleon is considered in the second order in the pion-nucleon coupling constant, corresponding to the dressing of the bare nucleons by the mesonic cloud. The inclusive and semi-inclusive deep inelastic processes on the deuteron involving off-shell nucleons are considered. A deformation of the mesonic cloud for the off-mass-shell nucleon, compared to the free one, generates observable effects in deep inelastic scattering. In particular, it leads to the breakdown of the convolution model, i.e. the deuteron structure functions are not expressed through the free nucleon structure function. Analysis of the semi-inclusive deep inelastic scattering on the deuteron, in the spectator approximation, shows that this reaction opens new possibilities to study the role of the off-shell effects in determining in detail the nucleon structure function.

nucl-th↗
arXiv1994

The Deuteron Spin Structure Functions in the Bethe-Salpeter Approach and the Extraction of the Neutron Structure Function $g_1^n(x)$

The nuclear effects in the spin-dependent structure functions $g_1^D$ and $b_2^D$ are calculated in the relativistic approach based on the Bethe-Salpeter equation with a realistic meson-exchange potential. The results of calculations are compared with the non-relativistic calculations. The problem of extraction of the neutron spin structure function, $g_1^n$, from the deuteron data is discussed.

hep-ph↗
arXiv1994

A Relativistic Approach to Deep Inelastic Scattering on the Deuteron

A covariant field theoretical approach to deep inelastic scattering on the deuteron is presented. The deuteron structure function is calculated in terms of the Bethe-Salpeter amplitude. Numerical calculations for the nucleon contribution are made with a realistic model of the $NN$-interaction, including $π$-, $ρ$-, $ω$-, $η$-, $δ$- and $σ$-mesons, and results are compared with previous non-relativistic calculations.

nucl-th↗