arXiv subjects
Publications and source records attributed to E. A. Kuraev.
The contributions to the electron-electron-photon vertex of two-loop electroweak corrections are calculated. The relative correction to the parity-violating asymmetry of Møller scattering for the case of 11 GeV electron scattered off the electron at rest is found to be about -0.0034 and should be taken into account at future experiment MOLLER at JLab.
The paper discusses the two-loop (NNLO) electroweak radiative corrections to the parity-violating Moller scattering asymmetry induced by insertions to boxes of electron and neutrino mass operators (fermion self-energies), vertex functions and boson self-energies. The results will be relevant to the ultra-precise 11 GeV MOLLER experiment planned at the Jefferson Laboratory, which will measure the weak charge of the electron and search for new physics. The numerical estimations for the NNLO contribution to the cross section asymmetry are presented.
Reactions induced by high energy antiprotons on proton on nuclei are accompanied with large probability by the emission of a few mesons. Interesting phenomena can be observed and QCD tests can be performed, through the detection of one or more mesons. The collinear emission from high energy (anti)proton beams of a hard pion or vector meson, can be calculated similarly to the emission of a hard photon from an electron \cite{Kuraev:2013izz}. This is a well known process in QED, and it is called the "Quasi-Real Electron method", where the incident particle is an electron and a hard photon is emitted leaving an 'almost on shell' electron impinging on the target \cite{Baier:1973ms}. Such process is well known as Initial State Emission (ISR) method of scanning over incident energy, and can be used, in the hadron case, to produce different kind of particles in similar kinematical conditions. In case of emission of a charged light meson, $π$ or $ρ$-meson, in proton-proton(anti-proton) collisions, the meson can be deviated in a magnetic field and detected. The collinear emission (along the beam direction) of a charged meson may be used to produce high energy (anti)neutron beams. This can be very useful to measure the difference of the cross sections of (anti)proton and (anti)neutron scattering from the target and may open the way for checking sum rules with antiparticles. Hard meson emission allows also to enhance the cross section when the energy loss from one of the incident particles lowers the total energy up to the mass of a resonance. The cross section can be calculated, on the basis of factorized formulas, where the probability of emission of the light mesons multiplies the cross section of the sub-process. Multiplicity distributions for neutral and charged meson production are also given.
The process of electron--positron annihilation into proton--antiproton pair is considered within the vicinity of $ψ(3770)$ resonance. The interference between the pure electromagnetic intermediate state and the $ψ(3770)$ state is evaluated. It is shown that this interference is destructive and the relative phase between these two contributions is large ($ϕ_0 \approx 250^o$).
In the one-photon exchange approximation we discuss questions related to the interpretation of unexpected results of the JLab polarization experiments to measure the Sachs form factors ratio $G_E/G_M$ in the region $1. 0 \leq Q^2 \leq 8.5$ GeV$^2$. For this purpose, we developed an approach which essentially is a generalization of the constituent-counting rules of the perturbative QCD (pQCD) for the case of massive quarks. We assume that at the lower boundary of the considered region the hard-scattering mechanism of pQCD is realized. Within the framework of the developed approach we calculated the hard kernel of the proton current matrix elements $J^{\pm δ, δ}_{p}$ for the full set of spin combinations corresponding to the number of the spin-flipped quarks, which contribute to the proton transition without spin-flip ($J^{δ, δ}_{p}$) and with the spin-flip ($J^{-δ, δ}_{p}$). This allows us to state that (i) around the lower boundary of the considered region, the leading scaling behavior of the Sachs form factors has the form $G_E, G_M \sim 1/Q^6$, (ii) the dipole dependence ($G_E, G_M \sim 1/Q^4$) is realized in the asymptotic regime of pQCD when $τ\gg 1$ ($τ=Q^2/4M^2$) in the case when the quark transitions with spin-flip dominate, (iii) the asymptotic regime of pQCD in the JLab experiments has not yet been achieved, and (iv) the linear decrease of the ratio $G_{E}/G_{M}$ at $τ< 1$ is due to additional contributions to $J^{δ, δ}_{p}$ by spin-flip transitions of two quarks and an additional contribution to $J^{-δ, δ}_{p}$ by spin-flip transitions of three quarks.
High-energy Coulomb correction to the screening angular parameter of the Moliere multiple scattering theory is found. Numerical calculations are presented in the range of nuclear charge from Z=4 to Z=82. The accuracy of the Moliere theory in determining the Coulomb correction to the screening angle is estimated.
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. Particular attention is devoted to the $ε$ dependence of radiative corrections, which is directly related to the electric proton form factor. We consider in particular the effects of the interference terms for soft and hard photon emission. Both quadratic amplitude describing the collinear emission along the scattered electron as well as the interference with the amplitudes of emission from the initial electron and the emission from protons are important in leading and next to leading approximation and they may compensate in particular kinematical conditions.
Analytic calculation are presented of the contribution to the anomalous magnetic moment of a muon from the channels of annihilation of an electron-positron pair to a pair of charged pi-mesons with radiative correction connected with the final state, as well as corrections to the lowest order kernel. The result with point-like pi-meson assumptions is $a_{point}=a_{point}^{(1)}+Δa_{point}$, $a_{point}^{(1)}=7.0866 \cdot 10^{-9}; Δa_{point}= -2.4 \cdot 10^{-10} .$ Taking into account the pion form factor in the frames of the Nambu-Jona-Lasinio (NJL) approach leads to $a_{NJL}=a_{NJL}^{(1)}+Δa_{NJL}$, $a_{NJL}^{(1)}= 5.48\cdot 10^{-8}; Δa_{NJL}=-3.43\cdot 10^{-9}$.
An extension of the QED 'return to resonance' mechanism to light meson emission ($π$, $ρ$) in (anti)proton collisions with a hadronic target (nucleon or nucleus) is proposed. The cross section and the multiplicity distributions are calculated. The collinear emission (along the beam direction) of a charged meson may be used to produce high energy (anti)neutron beams. Possible applications at existing and planned facilities are considered.
The mini-proceedings of the Workshop on "Constraining the hadronic contributions to the muon anomalous magnetic moment" which included the "13th meeting of the Radio MonteCarLow WG" and the "Satellite meeting R-Measurements at BES-III" held in Trento from April 10th to 12th, 2013, are presented. This collaboration meeting aims to bring together the experimental e+e- collider communities from BaBar, Belle, BESIII, CMD2, KLOE, and SND, with theorists working in the fields of meson transitions form factors, hadronic contributions to (g-2)_μand effective fine structure constant, and development of Monte Carlo generator and Radiative Corrections for precision e+e- and tau physics.
We calculate the transition form factor of the neutral pion where one photon is virtual and another photon is real in the model where the light constituent quark mass and the quark-pion vertex are taken to be momentum independent. Radiative corrections to the lowest order triangle quark Feynman amplitude are calculated. The resummation of the lowest radiative corrections to the virtual photon vertex is done by applying the Sudakov exponential hypothesis. Using fitting parameters, the quark mass and the strong coupling constant, the results on the pion transition form factor are compared with existing data published by CELLO, CLEO, BaBar and Belle collaborations.
The process of two pion production in the electron-polarized proton scattering is investigated. In the Weizsäcker-Williams approximation the differential spectral distributions and the spin-momentum correlations are considered. The spin correlation effects caused by $ρ$-meson widths are estimated to be of an order of several per cent. Both channels of the $π^+π^-$ and $π^+π^0$ creation are considered. The effects of intermediate excited baryons are not considered. The spectral distributions on pion energy fractions in polarized and unpolarized cases are presented analytically and numerically.
We calculate the bilinear combination of Dirac tensors describing the creation of a pair of charged particle (pi-meson or leptons) by virtual photons integrated on the final particle phase volume. It can be interpreted as an s channel discontinuity of the zero angle light-by-light scattering tensor with both photons off mass shell. The expression of light-by-light scattering tensor is represented in the form where the gauge invariance and the Bose symmetry are explicitly shown. Some applications and the checks are discussed.
The intermediate quarkonium state $χ_2(^3P_2)$ in electron-positron annihilation to proton and antiproton as well as in antiproton-proton annihilation to electron and positron can produce backward-forward asymmetry, when populated through two photon exchange. We use the dispersion relation method, which permits to express the asymmetry in terms of partial widths of quarkonium decay. The asymmetry dependence on the center of mass energy in the range near the resonance is presented. The comparison with a similar effect in these reactions with the neutral $Z$-boson in the intermediate state is given. We show that these effects are $\le 10^{-3}$. The main source of asymmetry is of pure QED origin ($\sim 10^{-2}$) which arises from the interference between initial and final state real photon emission.
We discuss questions related to the interpretation of unexpected results of measurements of the proton form factors ratio G_E/G_M in the polarization experiments done in JLab in the region of 0.5 < Q^2 < 8.5 GeV^2. For this purpose, in the case of the hard scattering mechanism we calculated (in the leading approximation) the matrix elements of the proton current J^{\pm δ,δ}_p for the full set of spin combinations corresponding to the number of the spin-flipped quarks, which contribute to the proton transition without spin-flip (J^{δ,δ}_p) and with the spin-flip (J^{-δ,δ}_p). This set is: (0,1), (0,3), (2,1), (2,3), where the first number in parentheses is the number of the spin-flipped quarks, which contribute to the J^{δ,δ}_p, and the second one is the number of the spin-flipped quarks which contribute to the J^{-δ,δ}_p. For the sets of (0,1) and (2,3), we found that the ratio G_E/G_M ~ 1, and the form factors G_E and G_M behave for the set of (0,1) as G_E, G_M ~ 1/Q^6, and for the set of (2,3) as G_E, G_M ~ 1/Q^4. At the same time the set of (0,1) is realized for τ<< 1, and the set (2,3) for τ>> 1 (τ=Q^2/4m^2). This allows us to suppose that: 1) at the lower boundary of the experimental measurements of the ratio G_E/G_M not dipole dependence appears but the law of G_E, G_M ~ 1/Q^6; 2) the conditions for the observation of the dipole dependence in the experiments has not yet been achieved; 3) since for quarks J^{δ,δ}_q ~ 1 and J^{-δ,δ}_q ~ \sqrtτ, then the dipole dependence is realized when τ>> 1 in the case when the quark transitions with spin-flip are dominate.
We study the production of spin-one mesons in high-energy heavy-ion collisions with peripheral kinematics in the framework of QED. The cross sections of the production of a single vector meson and of two different ones are presented. The explicit dependence on the virtuality of the intermediate vector meson is obtained within a quark model. The effect of reggeization of the intermediate vector meson state in the case of the production of two vector mesons is taken into account.
This paper has been withdrawn by the authors since it was strongly elaborated, some new sections appeared. This made the paper significantly differ from current version. Besides two new authors participated in the work. So the authors believe that new version of paper should be considered as a new submission to appear later.
World data on the lepton-charge asymmetry in the elastic and inelastic lepton scattering off the proton and nuclei are compiled and discussed. After reviewing the published results, we compare the elastic data to a model calculation of the two-photon exchange mechanism. We show that the existing data do not provide any evidence for the two-photon contribution. At significance level 0.05 the data allow to exclude the two-photon exchange as an explanation for the difference between Rosenbluth and polarization measurements of proton electromagnetic form factors.