arXiv subjects
Publications and source records attributed to E. A. Kuraev.
In this note we give arguments in favor of the statement that the contribution of the box diagram calculated for electron muon elastic scattering can be considered an upper limit to electron proton scattering. As an exact QED calculation can be performed, this statement is useful for constraining model calculations involving the proton structure.
Radiative decays of pseudoscalar and vector mesons are calculated in the framework of the chiral Nambu-Jona-Lasinio (NJL) model. We use the amplitude for triangle quark loops of anomalous type. In evaluating these loop integrals we use two methods. In the first one, we neglect the dependence of external momenta by reproducing the Wess-Zumino-Witten terms of effective chiral meson Lagrangian. In the second method, we take into account the momentum dependence of loop integrals omitting their imaginary part. This makes it possible to allow for quark confinement. As applied both the methods is in qualitative agreement with each other and with experimental data. The second method allows us to describe the electron-positron annihilation with production of $η'$ and $ρ$ mesons in the center of mass energy range from 1.6 to 3.5$\GeV$. The comparison with the recent experimental data is presented.
The cross section for different processes induced by $e^+e^-$ annihilation, in the kinematical limit $β_μ\approxβ_π=(1-m_π^2/ε^2)^{1/2}\sim 1$, is calculated taking into account first order corrections to the amplitudes and the corrections due to soft emitted photons, with energy $ω\leΔE\le ε$ in the center of mass of the $e^+e^-$ colliding beams. The results are given separately for charge--odd and charge--even terms in the final channels $π^+π^-(γ)$ and $μ^+μ^-(γ)$. In case of pions, form factors are taken into account. The differential cross sections for the processes: $e^++e^-\to e^++e^-(+γ)$, $\to π^++π^-(γ)$, $\to μ^++μ^-(γ),\to γγ(γ)$ have been calculated and the corresponding formula are given in the ultrarelativistic limit $\sqrt{s}/2= ε\gg m_μ\sim m_π$ . For a quantitative evaluation of the contribution of higher order of the perturbation theory, the production of $π^+π^-$, including radiative corrections, is calculated in the approach of the lepton structure functions. This allows to estimate the precision of the obtained results as better than 0.5% outside the energy region corresponding to narrow resonances. A method to integrate the cross section, avoiding the difficulties which arise from singularities is also described.
Cross section of the processes of neutral pion production as well as pairs of charged fermions and bosons in peripherical interaction of leptons, photons are calculated in main logarithmical approximation. We investigate the phase volumes and differential cross sections. The differential cross section of few neutral pions and a few pairs production are written down explicitly. Considering the academic problem of summation on the number of pairs for the case of massless particles we reproduce the known results obtained in seventies of last century. The possibility to construct the generator for Monte-Carlo modeling of this processes basing of this results are discussed.
We investigate the effect of high order radiative corrections in unpolarized electron proton elastic scattering and compare with the calculations at lowest order, which are usually applied to experimental data. We show that higher order terms play a role, starting from values of the momentum transfer squared, $Q^2$, larger than the electron mass. Particular attention is devoted to the $ε$ dependence of radiative corrections.
Born cross section and the radiative corrections to its lowest order are considered in the frame work of QED with structureless nucleons including the emission of virtual and real photons. Result is generalized to take into account radiative corrections in higher orders of perturbation theory in the leading and next-to leading logarithmic approximation. Crossing processes are considered in the leading approximation.
We reconsider QED radiative corrections (RC) to the $π^{0}\to e^{+}e^{-}$ decay width. One kind of RC investigated earlier has a renormalization group origin and can be associated with the final state interaction of electron and positron. It determines the distribution of lepton pair invariant masses in the whole kinematic region. The other type of RC has a double-logarithmic character and is related to almost on-mass-shell behavior of the lepton form factors. The total effect of RC for the $π^{0}\to e^{+}e^{-}$ decay is estimated to be 3.2% and for the decay $η\to e^{+}e^{-}$ is 4.3%.
Born differential cross sections and the lowest-order radiative correction to them are obtained in the kinematics of large-angle final photons emission in high-energy electron-positron annihilation processes. Taking into account possible emission of real soft and hard photons in collinear kinematics we show the validity of the Drell-Yan form of differential cross section with the nonsinglet structure functions of initial leptons. The leading and next-to leading contribution to the cross sections is obtained. The relevant numerical estimations are presented.
Process of lepton pair production by polarized photon on nuclei can be used to measure the degree of linear polarization of high energy photon. The differential cross section and the analyzing power are calculated with taking into account higher powers of expansion on $Zα$. Pure Coulomb and screened potential are considered.
The decay ϕ-> f_0(980) γand process e^+e^- -> ϕf_0(980) are considered within the local Nambu-Jona-Lasinio model. In the amplitudes of these processes contributions of s-quark and kaon loops are taken into account. The kaon loop gives a dominant contribution. Our estimation for the decay width of ϕ-> f_0 γis in satisfactory agreement with recent experimental data. This allows us to make some predictions for cross sections of the process e^+e^- -> γ^* -> ϕf_0 which can be tested in the C-τfactory. The total and differential cross sections of this process are calculated and presented in the figures.
In frames of effective Regge action the vertices describing conversion of two reggeized gluons to one two and three ordinary gluons was constructed. The self-consistency: Bose symmetry and gauge invariance properties checks was shown to be fulfilled. The simplest one with creation of a single gluon was intensively verified in programs of experimental and theoretical treatment since it determine the kernel of of the known BFKL equation. Here we discuss the possibility to check the vertex with creation of two real gluons, which can reveal itself in process of scalar mesons production in high energy peripheral nucleons collisions. We show that the mechanisms which include emission of two gluons in the same effective vertex contribution dominate compared with one with the creation of two separate gluons. Numerical estimations of cross section of pair of charged pions production for LHC facility give the value or order $10 mb$. As well we estimate the excess of production of positively charged muons (as a decay of pions) created by cosmic ray proton collisions with the atmosphere gas nuclei to be in a reasonable agreement with modern data.
The two photon exchange amplitude is investigated in frame of analytic properties of the virtual Compton scattering amplitude as a function of the invariant mass squared of the intermediate hadronic state. A sum rule is built, based on arguments from analyticity. It relates the differential cross section of elastic electron-proton scattering including form factors, and the cross section of inelastic scattering channel, with a contribution of nucleon anti-nucleon pair production arising from the Fermi statistics. The last term is calculated in frame of a simple model of nucleon-pion interaction.
Charge asymmetry in electron (positron) scattering arises from the interference of the Born amplitude and the box-type amplitude corresponding to two virtual photons exchange. It can be extracted from electron proton and positron proton scattering experiments, in the same kinematical conditions. Considering the virtual photon Compton scattering tensor, which contributes to the box-type amplitude, we separate proton and inelastic contributions in the intermediate state and parametrize the proton form-factors as the sum of a pure QED term and a strong interaction term. Arguments based on analyticity are given in favor of cancellation of contributions from proton strong interaction form factors and of inelastic intermediate states in the box type amplitudes. In frame of this model, with a realistic expression for nucleon form-factors, numerical estimations are given for moderately high energies.
Radiative corrections in leading logarithmic approximation are calculated for the differential cross section of $e^- μ^+$ radiative scattering. In particular the interference term due to photon emission from electron and muon blocks are calculated in helicity independent and dependent parts. The calculation is applied to the kinematical conditions of existing DVCS data in electron-proton collisions. Both helicity odd and helicity even differential cross sections are considered.
We look for asymmetries in the angular distributions of events from recent data on $e^+ +e^-\to p +\bar p +γ$ from BABAR collaboration. From first principles, as the C-invariance of the electromagnetic interaction and the crossing symmetry, the presence of two-photon exchange would create a forward backward asymmetry in the data. The analysis of the available data shows no asymmetry, within an error of 2%. This result is consistent with a structureless model for the proton, based on a calculation of $e^+ +e^-\to μ^+ + μ^- +γ$ with a proper replacement of the muon mass. As no systematic deviations are seen, we can conclude that these data do not give any hint of the presence of the two photon contribution, in all the considered kinematical range.
Considering very high energy peripheral electron-hadron scattering with a production of hadronic state X moving closely to the direction of initial hadron the Weizsäcker-Williams like expression, relating the difference of q^2-dependent differential cross-sections of DIS processes to the convergent integral over the difference of the total hadron photo-production cross-sections on hadros, is derived. Then, exploiting analytic properties of the forward retarded Compton scattering amplitude on the same hadrons, first, the sum rules are derived bringing into relation hadron electromagnetic form factors with the difference of the q^2-dependent differential cross-sections of DIS, then using Weizsäcker-Williams like expression and taking the derivative of both sides according to ${\bf q^2}$ for ${\bf q^2} \to 0$ one comes to new universal hadron sum rules relating hadron static parameters to the convergent integral over the difference of the total hadron photo-production cross-sections on hadrons.
The amplitude of zero angle scattering of electron on photon in the 3-rd QED order of fine structure constant with $γ^*γ$ intermediate state converting into quark--antiquark is considered. Utilizing analytic properties of elastic photon--photon scattering amplitude an explicit expression for differential cross- section of quark--antiquark pair production at electron-photon collision in peripheral kinematics is derived apparently. Limiting case of small transferred momenta with an application of the Weizsäcker-Williams like relation gives the sum rule for photon target, bringing into the relation the sum of ratios of the four power of the quark charges to squared quark masses with integral over the total $γγ\to 2 jets$ cross--section.
Estimation of multiplicity of muons and pions production at high energy proton-nuclei collisions is given. Both QED and QCD contributions are considered for peripheral kinematics of muon pair and $σ$-meson production, keeping in mind it's final conversion to muons. An attempt to explain the excess of positive charged muons compared to negative one in cosmic muon showers is given. We derive the dependence of cross-section of $n$ pairs as a function of $n$ at large n as $d^n(n!n^2)^{-1}$.