Synchrotron radiation in a chromo-magnetic field

We study the generalization of QED synchrotron radiation to the QCD case with a chromomagnetic field using the Schwinger {\it et al} source method. It is shown that the QED case can be obtained as a special limit. The comparison with the path integral approach of Zakharov has shown consistent results.Comment: Accepted for publication in Phys. Rev.

Model independent study of massive lepton elastic scattering on the proton, beyond the Born approximation

Model independent expressions for all polarization observables in $\mu+p\to \mu+p$ elastic scattering are obtained, taking into account the lepton mass and including the two-photon exchange contribution. The spin structure of the matrix element is parametrized in terms of six independent complex amplitudes, functions of two independent kinematical variables. General statements about the influence of the two--photon--exchange terms on the differential cross section and on polarization observables are given. Polarization effects have been investigated for the case of a longitudinally polarized lepton beam and polarized nucleon in the final state.Comment: 28 pages, 3 figure

Experimental constraint on the ρ−\rho - meson form factors in the time--like region

The annihilation reaction $e^++e^-\rightarrow \bar \rho+\rho$ is considered. The constraint on time-like $\rho$-meson form factors from the measurement done by the BaBar collaboration at $\sqrt{s}=10.5$ GeV is analyzed.Comment: 10 pages 3 figure

Proton electron elastic scattering and the proton charge radius

It is suggested that proton elastic scattering on atomic electrons allows a precise measurement of the proton charge radius. Very small values of transferred momenta (up to four order of magnitude smaller than the ones presently available) can be reached with high probability.Comment: 4 pages, 4 figure

General analysis and numerical estimations of polarization observables in Nˉ+N→π+e++e−\bar N+N\to \pi+ e^++e^- reaction in an exclusive experimental setup

The dependence of the differential cross section and polarization observables in the $\bar N+N\to \pi +e^++e^-$ reaction on the polarizations of the proton target and antiproton beam (the produced electron may be unpolarized or longitudinally polarized) have been derived in a general form using hadron electromagnetic current conservation and $P-$ invariance of the hadron electromagnetic interaction. The analysis was done for the case of an exclusive experimental setup where the produced electron and pion are detected in coincidence. The explicit dependence of all polarization observables on two, from five, kinematic variables (the azimuthal angle $\varphi$ and the virtual-photon parameter $\epsilon$), have been obtained assuming one-photon-exchange. The application to the particular case of a mechanism which contains information on time-like proton form factors in the unphysical region is considered in the Born approximation.Comment: arXiv admin note: substantial text overlap with arXiv:1011.401

Proton-antiproton annihilation into massive leptons

We extend previous calculations of polarization observables for the annihilation reaction $\bar p +p\to \ell^{-}+\ell^{+}$ to the case of heavy leptons, such as the $\tau$-lepton. We consider the case when the beam and/or the target are polarized, as well as the polarization of the outgoing leptons. We give the dependence of the unpolarized cross section, angular asymmetry, and various polarization observables on the relevant kinematical variables in the center of mass and in the laboratory system, with particular attention to the effect of the mass induced terms.Comment: 25 pages, 8 figure

Polarization effects in elastic proton-electron scattering

Proton elastic scattering from electrons at rest is calculated in the Born approximation. The interest of this reaction is related to the possibility of polarizing high energy antiproton beam and to high energy proton polarimetry. The differential cross section and polarization observables have been derived assuming one photon exchange. Numerical estimates are given for the cross section and the spin correlation coefficients in a wide kinematical range.В Борновском приближении вычислено упругое рассеяние протонов на покоящихся электронах. Интерес к этой реакции обусловлен возможностью поляризации высокоэнергетического антипротонного пучка и поляриметрией протонов высоких энергий. В предположении однофотонного обмена получены выражения для дифференциального сечения и поляризационных наблюдаемых. Выполнены численные оценки сечения и коэффициентов корреляции спина в широкой кинематической области.У Борнівському наближенні обчислено пружне розсіювання протонів на електронах, які знаходяться у стані спокою. Інтерес до цієї реакції обумовлено можливістю поляризації високоенергетичного антипротонного пучка та поляриметрією протонів високих енергій. У передбаченні однофотонного обміну одержані вирази для диференційного перерізу та поляризаційних спостережуваних. Виконані чисельні оцінки перерізу та коефіцієнтів кореляції спінів у широкій кінематичній області

A model for space and time-like proton (neutron) form factors

A model is suggested to describe the known experimental behavior of nucleon form factors both in space and time-like regions. It implies quarks to be colorless in the region of high intensity chomo-magnetic gluon field inside the nucleon.Comment: 6 pages, 3 figure

Feasibility studies of time-like proton electromagnetic form factors at PANDA at FAIR

Simulation results for future measurements of electromagnetic proton form factors at \PANDA (FAIR) within the PandaRoot software framework are reported. The statistical precision with which the proton form factors can be determined is estimated. The signal channel $\bar p p \to e^+ e^-$ is studied on the basis of two different but consistent procedures. The suppression of the main background channel, $\textit{i.e.}$ $\bar p p \to \pi^+ \pi^-$, is studied. Furthermore, the background versus signal efficiency, statistical and systematical uncertainties on the extracted proton form factors are evaluated using two different procedures. The results are consistent with those of a previous simulation study using an older, simplified framework. However, a slightly better precision is achieved in the PandaRoot study in a large range of momentum transfer, assuming the nominal beam conditions and detector performance