arXiv subjects

A. I. Machavariani

Publications and source records attributed to A. I. Machavariani.

12 recordsLinked to original sources

arXiv2018

On the $ρ^o$-meson production in the inclusive proton-proton collision

The production of the $ρ^o$- meson in the inclusive proton-proton scattering $p_A+p_B\to ρ^o+X$ is studied using extension of parton model according to generalized vector meson dominance model (GVMD) in region of small $Q^2=m_{ρ^o}^2$ and $ρ^o$-meson transverse momentum $\le 1-2GeV/c$. The realistic description of the experimental cross sections of $p_A+p_B\to ρ^o+X$ for $4.9\le \sqrt{s}\le 65 GeV$ is achieved using an isotropic distribution of the $ρ^o$-meson. The resulting density matrix allows one to select values of the quark masses, which lead to the isotropic distribution of the emitted meson. It is demonstrated that the same cross sections of the reaction $p_A+p_B\toρ^o +X$ for the isotropic distribution of the $ρ^o$-meson can be obtained with different sets of the quark masses and corresponding coupling constants of the quark-meson vertex functions.

hep-ph↗

arXiv2014

On the field theoretical formulation of the electron-proton scattering in the Coulomb and Lorentz gauges

The relativistic three dimensional (3D) Lippmann-Schwinger-type equations for the $ep$ scattering amplitude is derived based on unitarity condition in the usual quantum electrodynamic (QED). The $ep$ scattering potential $V_{e'N',eN}$ consists of the leading one off mass shell photon exchange part and the nonlocal multi-particle exchange potential. Unlike to the other field-theoretical equations, both protons in the unitarity condition and in $V_{e'N',eN}$ are on mass shell. Therefore in this approach are not required the multi-variable input photon-nucleon vertexes with the off mass shell nucleons. In the present formulation the standard leading one photon exchange potential $V_{OPE}$ is generated by the canonical equal-time anti commutator between the electron source and the interacted electron fields which are sandwiched by the one nucleon asymptotic states. This anticommutator is calculated in the Coulomb and Lorentz gauges, where only the transverse parts of the photon fields are quantized. It is shown, that the leading one photon exchange potentialn$V_{OPE}$ in the Coulomb and Lorentz gauges coincide. The complete set of the next to leading order terms which are generated by the static electric (Coulomb) interaction are exactly reproduced.

nucl-th↗

arXiv2014

Conformal transformations and doubling of the particle states

The 6D and 5D representations of the four-dimensional (4D) interacted fields and the corresponding equations of motion are obtained using equivalence of the conformal transformations of the four-momentum $q_μ$ ($q'_μ=q_μ+h_μ$, $q'_μ=Λ^ν_μq_ν$, $q'_μ=λq_μ$ and $q'_μ=-M^2q_μ/q^2$) and the corresponding rotations on the 6D cone $κ_Aκ^A=0$ $(A=μ;5,6\equiv 0,1,2,3;5,6)$ with $q_μ=M\ κ_μ/(κ_{5}+κ_{6})$ and the scale parameter $M$. The 4D reduction of the 6D fields on the cone $κ_Aκ^A=0$ require the intermediate 5D projection of the fields which are placed into two 5D hyperboloids $q_μq^μ+ q_5^2= M^2$ and $q_μq^μ- q_5^2=- M^2$ in order to cover the whole domain $(-\infty,\infty)$ of $q^2\equiv q_μq^μ$ with $(q_5^2\ge 0$. The resulting 5D and 4D fields $φ(x,x_5=0)=Φ(x)$ in the coordinate space consist of two parts $φ=φ_1+φ_2$ and $Φ=Φ_1+Φ_2$, where the Fourier conjugate of $φ_1(x,x_5)$ and $φ_2(x,x_5)$ are defined on the hyperboloids $q_μq^μ+ q_5^2= M^2$ and $q_μq^μ- q_5^2=- M^2$ respectively. The present relationship between the 6D, 5D and 4D fields require two kinds of 5D fields $φ_{\pm}=φ_1\pmφ_2$ and their 4D reductions $φ_{\pm}(x_5=0)=Φ_{\pm}=Φ_1\pmΦ_2$ with the same quantum numbers and with the different masses and the source operators. This doubling of the 4D fields $Φ_{\pm}=Φ_1\pm Φ_2$ is in agreement with the observed mass splitting of the electron and muon, $π$ and $π(1300)$-mesons, N and N(1440)-nucleons etc [1].

math-ph↗

arXiv2008

Current conservation, screening and the magnetic moment of the $Δ$ resonance. -- 1. Formulation without quark degrees of freedom

The pion-nucleon bremsstrahlung $π+N\Longrightarrowγ'+π'+N'$ is studied in a new form of current conservation. According to this condition, the internal and external particle radiation parts of the $πN$ radiation amplitude have opposite signs, i.e., they contain terms which must cancel each other. Therefore, one has a screening of the internal and external particle radiation in the $πN$ bremsstrahlung. In particular, it is shown that the double $Δ$ exchange diagram with the $Δ-γ' Δ'$ vertex cancel against the appropriate longitudinal part of the external particle radiation diagrams. Consequently, a model independent relation between the magnetic dipole moments of the $Δ^+$ and $Δ^{++}$ resonances and the anomalous magnetic moment of the proton $μ_p$ is obtained, where $μ_Δ$ is expressed by $μ_p$ as $μ_{Δ^+}={{M_Δ}\over {m_p}} μ_p$ and $μ_{Δ^{++}}={3\over 2}μ_{Δ^+}$ in agreement with the values extracted from the fit for the experimental cross section of the $π^+ p\toγ'π^+ p$ reaction.

nucl-th↗

arXiv2008

Current conservation, screening and the magnetic moment of the $Δ$ resonance: 2. Formulation with quark degrees of freedom 3. Magnetic moment of the $Δ^o$ and $Δ^-$ resonances

Our previous paper \cite{MFNEW} is generalized within the field theoretical formulation with the quark degrees of freedom \cite{HW,H,N,Z}, where pions and nucleons are treated as the bound systems of quarks. It is shown that relations generated by current conservation for the on shell $πN$ bremsstrahlung amplitude with composite nucleons and pions have the same form as in the usual quantum field theory \cite{IZ,BD} without quark degrees of freedom \cite{MFNEW}. Consequently, the model independent relations for the magnetic dipole moments of the $Δ^+$ and $Δ^{++}$ resonances in \cite{MFNEW} remain be the same in the quantum field theory with the quark degrees of freedom. These relations are extended for the magnetic dipole moments of the $Δ^o$ and $Δ^-$ resonances which are determined via the anomalous magnetic moment of the neutron $μ_n$ as $μ_{Δ^o}={{M_Δ}\over {m_p}} μ_n$ and $μ_{Δ^{-}}={3\over 2}μ_{Δ^o}$.

nucl-th↗

arXiv2007

Ward-Takahashi identity, soft photon theorem and the magnetic moment of the $Δ$ resonance

Starting from the Ward-Takahashi identity for the radiative $πN$ scattering amplitude a generalization of the soft photon theorem approach is obtained for an arbitrary energy of an emitted photon. The external particle radiation part of the $πN\toγ'π'N' $ amplitude is analytically reduced to the double $Δ$ exchange amplitude with the $Δ\toγ'Δ'$ vertex function. We have shown, that the double $Δ$ exchange amplitudes with internal $Δ$ radiation is connected by current conservation with the corresponding part of the external particle radiation terms. Moreover according to the current conservation the internal and external particle radiation terms with the $Δ-γ'Δ'$ vertex have a opposite sign i.e. they must cancel each other. Therefore we have a screening of the internal double $Δ$ exchange diagram with the $Δ-γ' Δ'$ vertex by the external particle radiation. This enables us to obtain a model independent estimation of the dipole magnetic moment of $Δ^+$ and $Δ^{++}$ resonances $μ_Δ$ through the anomalous magnetic moment of the proton $μ_p$ as $μ_{Δ^+}={{M_Δ}\over {m_p}} μ_p$ and $μ_{Δ^{++}}={3\over 2}μ_{Δ^+}$ in agreement with the values obtained from the fit of the experimental cross section of the $π^+ p\toγ'π^+ p$ reaction.

nucl-th↗

arXiv2006

On relationship between conformal transformations and broken chiral symmetry

Starting with the conformal transformations in the momentum space, the nonlinear $σ$-model and the standard model with the spontaneous broken $SU(2)\times U(1)$ symmetry are reproduced. The corresponding chiral Lagrangians are given in the five dimensional form because for the conformal transformations of the four-momentum $q_μ$ ($q'_μ=q_μ+h_μ$, $q'_μ=Λ^ν_μq_ν$, $q'_μ=λq_μ$ and $q'_μ=-M^2q_μ/q^2$) the equivalence rotations in the 6D space were used. The derived five dimensional Lagrangians consists of the parts defined in the two different region $q_μq^μ\pm q_5^2=\pm M^2$ which are connected by the inversion $q'_μ=-M^2 q_μ/q^{2}$, where $M$ is a scale parameter. For the $σ$-model $M$ is determined by the pion mass $M^2= m_π^2/2$. For the 5D Lagrangian with the spontaneous broken $SU(2)\times U(1)$ symmetry the scale parameter $M^2$ is defined by the Higgs particle mass $8m^2_{Higgs}=9M^2$. Unlike to the usual four-dimensional formulation in the present approach the chiral symmetry breaking terms are obtained from the conformal transformations and it is demonstrated, that the corresponding interaction parts of Lagrangians have the opposite sign in the regions $q^μq_μ>M^2$ and $0\le q^μq_μ<M^2$.

math-ph↗

arXiv2005

Conformal group of transformations of the quantum field operators in the momentum space and the five dimensional Lagrangian approach

Conformal group of transformations in the momentum space, consisting of translations $p'_μ=p_μ+h_μ$, rotations $p'_μ=Λ^ν_μp_ν$, dilatation $p'_μ=λp_μ$ and inversion $p'_μ= -M^2p_μ/p^2$ of the four-momentum $p_μ$, is used for the five dimensional generalization of the equations of motion for the interacting massive particles. It is shown, that the ${\cal S}$-matrix of the charged and the neutral particles scattering is invariant under translations in a four-dimensional momentum space $p'_μ=p_μ+h_μ$. In the suggested system of equations of motion, the one-dimensional equations over the fifth coordinate $x_5$ are separated and these one dimensional equations have the form of the evaluation equations with $x_5=\sqrt{x_o^2-{\bf x}^2}$. The important property of the derived five dimensional equations of motion is the explicit separation of the parts of these equations according to the inversion $p'_μ=-M^2 p_μ/p^{2}$, where $M$ is a scale constant.

hep-th↗

arXiv2003

Relativistic field-theoretical formulation of the three-dimensional equations for the three fermion system

A new kind of the relativistic three-body equations for the three fermion systems are suggested. These equations are derived in the framework of the standard field-theoretical $S$-matrix approach in the time-ordered three dimensional form. Therefore corresponding relativistic covariant equations are three-dimensional from the beginning. The solutions of the considered equations satisfy automatically the unitarity condition and for the leptons these equations are exactly gauge invariant even after the truncation over the multiparticle ($n>3$) intermediate states. Moreover, the form of these three-body equations does not depend on the choice of the model Lagrangian and it is the same for the formulations with and without quark degrees of freedom. The effective potential of the suggested equations is defined by the vertex functions with two on-mass shell particles. It is emphasized that these INPUT vertex functions can be constructed from experimental data. Special attention is given to the comparison with the three-body Faddeev equations. Unlike to these equations, the suggested three-body equation have the form of the Lippmann-Schwinger-type equations with the connected potential. In addition, the microscopical potential of the suggested equations contains the contributions from the three-body forces and from the particle creation (annihilation) mechanism on the one external particles. The structure of the three-body forces, appearing in the considered field-theoretical formulation, is analyzed.

nucl-th↗

arXiv2003

Field-theoretical three-body relativistic equations for the multichannel $πN <-> γN <-> ππN <-> γπN$ reactions

A new kind of the relativistic three-body equations for the coupled $πN$ and $γN$ scattering reactions with the $ππN$ and $γπN$ three particle final states are suggested. These equations are derived in the framework of the standard field-theoretical $S$-matrix approach in the time-ordered three dimensional form. Therefore corresponding relativistic covariant equations are three-dimensional from the beginning and the considered formulation is free of the ambiguities which appear due to a three dimensional reduction of the four dimensional Bethe-Salpeter equations. The solutions of the considered equations satisfy the unitarity condition and are exactly gauge invariant even after the truncation of the of the multiparticle ($n>3$) intermediate states. Moreover the form of these three-body equations does not depend on the choice of the model Lagrangian and it is the same for the formulations with and without quark degrees of freedom. The effective potential of the suggested equations is defined by the vertex functions with two on-mass shell particles. It is emphasized that these INPUT vertex functions can be constructed from experimental data. Special attention is given to the construction of the intermediate on shell and off shell $Δ$ resonance states. These intermediate $Δ$ states are obtained after separation of the $Δ$ resonance pole contributions in the intermediate $πN$ Green function. The resulting amplitudes for the $Δ\Longleftrightarrow Nπ$; $Δ\Longleftrightarrow Nγ;$ $% Δ^{\prime}\Longleftrightarrow Δγ$ transition have the same structure as the vertex functions for transitions between the on mass shell particle states with spin 1/2 and 3/2.

nucl-th↗

arXiv2002

Relativistic field-theoretical approach to the inverse scattering problem

The inverse scattering problem for the relativistic three-dimensional equation $\Bigl(2E_{\bf p'}-2E_{\bf p}\Bigr)<{\bf p'}|Ψ_{\bf p}>= -\int V(t)d^3{\bf p''}<{\bf p''}|Ψ_{\bf p}>$ with $E_{\bf p}=\sqrt{m^2+{\bf p}^2}$ and $t=\Bigl(E_{\bf p'}-E_{\bf p''}\Bigr)^2 -\Bigl({\bf p'}-{\bf p''}\Bigr)^2$ is considered. The field-theoretical potential $V(t)$ of this equation is constructed in the framework of the old perturbation theory. It contains all contributions of diagrams with intermediate off-mass shell particles. In particular, this potential reproduces the OBE Bonn model of the $NN$ potential exactly.For the $πN$ scattering it is generated by $σ,ρ, ω$-meson exchange diagrams. The inverse scattering problem is solved by reduction of these relativistic equations to the standard Schrödinger equations $\Bigl(Δ_{\bf r}+{\bf k}^2\Bigr)<{\bf r}|ϕ_{\bf p}>= - v({\bf r})<{\bf r}|ϕ_{\bf k}>$ with $E_{\bf p}={\bf k}^2/2m+m$. The relation between the relativistic potential $V(t)$ and its nonrelativistic representation $v({\bf r})$ is obtained.

nucl-th↗

arXiv2002

Field-theoretical description of the multichannel gamma-p scattering reaction in the Delta resonance region and determination of the magnetic moment of the Delta+ resonance

The cross-sections of the $γp-γ' N'$, $γp-π' N'$ and $γp-γ'π' N'$ reactions are calculated in the framework of the field-theoretical one-particle ($π,ω,ρ$-mesons, nucleon and $Δ$-resonance) exchange model. Unlike the other relativistic approaches, our resulting amplitudes of the $γp$ multichannel reactions require one-variable covariant vertex functions as input ingredient and every diagram of these amplitudes satisfies the current conservation condition in the Coulomb gauge. The complete set of the model independent skeleton diagrams for the $γ p\toγ'π'N'$ reaction is presented. The separable model of the $πN$ interaction is generalized to construct the spin 3/2 particle propagator of the $Δ$-resonance. This procedure allows to obtain the $πN-Δ$ form factor and $Δ$ propagator directly from the $πN$ $P_{33}$ phase shifts. The numerical calculation of the differential cross section of the $γp-γ' N'$, $γp-{π^o}' N'$ and $γp-γ'{π^o}'N'$ reactions are performed with two different separable models of the $Δ$ propagator and with the propagator of Breit-Wigner shape. It is demonstrated that the numerical description of these reactions in the $Δ$-resonance region are very sensitive to the form of the $Δ$-propagator. The sensitivity of the cross-sections of the $γp\toγ'{π^o}'p'$ reaction to the magnitude of the $Δ^+$ magnetic moment is examined and the most convenient kinematical region for the determination of the magnetic moment of the $Δ^+$-resonance from the forthcoming data is indicated.

nucl-th↗