Radiative electron-proton scattering is studied in peripheral kinematics, where the scattered electron and photon move close to the direction of the initial electron. Even in the case of unpolarized initial electron the photon may have a definite polarization. The differential cross sections with longitudinally or transversal polarized initial electron are calculated. The same phenomena are considered for the production of an electron-positron pair by the photon, where the final positron (electron) can be also polarized. Differential distributions for the case of polarized initial photon are given. Both cases of unscreened and completely screened atomic targets are considered.
The polarization of bremsstrahlung photon in the processes $ee^\pm\to (eγ)e^\pm$, and $ep\to (eγ)p$ is calculated for peripheral kinematics, in the high energy limit where the cross section does not decrease with the incident energy. When the initial electron is unpolarized(longitudinally polarized) the final photon can be linearly (circularly) polarized. The Stokes parameters of the photon polarization are calculated as a function of the kinematical variables of process: the energy of recoil particle, the energy fraction of scattered electron, and the polar and azimuthal angles of photon. Num…
We present a calculation of the complete $O(α)$ electroweak radiative corrections to the Moller scattering process e^-e^- -> e^-e^-, including hard bremsstrahlung contributions. We study the effects of these corrections on both the total cross section and polarization asymmetry measured in low energy fixed target experiments. Numerical results are presented for the experimental cuts relevant for E-158, a fixed target e^-e^- experiment being performed at SLAC; the effect of hard bremsstrahlung is to shift the measured polarization asymmetry by approximately +4%. We briefly discuss the remaining…
Bremsstrahlung from relativistic electrons is considered under conditions when some transverse direction of momentum transfer is statistically preferred. It is shown that in the dipole approximation all the medium anisotropy effects can be accumulated into a special modulus-bound transverse vector, $\bm N$. To exemplify a target with $N^2\sim1$, we calculate radiation from electron incident at a small angle on an atomic row in oriented crystal. Radiation intensity and polarization dependence on the emission angle and frequency for constant $\bm N$ is investigated. Net polarization for the angl…
An economic technique for calculation of polarized bremsstrahlung process is proposed, assuming typical atomic momentum transfer $q\ll m$. The adopted approach is based on the natural reduction of the matrix element to the form $V^αγ^α+A_{5}γ^{5}$. Polarization distribution in the fully differential cross-section is analyzed. It is found that at a given momentum transfer to the atom polarization in the plane of small radiation angles is oriented along circles passing through two common points. It is shown that with angular selection of radiated photons carried out, even with momentum transfers…
This paper continues the approach of Kostenko \& Thompson to calculating quantum electrodynamic processes in the ultrastrong magnetic field near some neutron stars, such as magnetars or merging binary neutron stars. Here we consider electron-positron scattering, the Coulomb scattering of electrons and positrons off ions, and relativistic $e^\pm$-ion bremsstrahlung. The evaluation of differential and total cross sections simplifies considerably when the magnetic field lies in the range $10^3B_{\rm Q} \gg B \gg B_{\rm Q}$, where $B_{\rm Q} \equiv m^2/e = 4.4\times 10^{13}$ G. Then, relativistic …
The quantum mechanical treatment of quadrupole radiation due to bremsstrahlung exact to all orders in the Coulomb interaction of two non-relativistically colliding charged spin-0 and unpolarized spin-1/2 particles is presented. We calculate the elements of the quadrupole tensor, and present analytical solutions for the double differential photon emission cross section of identical and non-identical particles. Contact is made to Born-level and quasi-classical results in the respective kinematic limits and effective energy loss rates are obtained. A generally valid formula for soft-photon emissi…
We discuss the dark gauge boson emission from neutron stars via nucleon-nucleon bremsstrahlung. Through the rigorous treatment of the effective field theory prescription and the thermal effect, we derive the relevant couplings of dark gauge bosons to hadrons in medium. As a specific example, the $U(1)_{\rm B-L}$ gauge boson scenario is chosen to investigate dark gauge boson emissivities during supernovae and cooling of young neutron stars. From the stellar cooling argument, we obtain the constraints on the $\rm B-L$ gauge coupling for given gauge boson masses in two observations: the duration …
Edge effects in spectra of non-dipole radiation from ultra-relativistic electrons passing through various finite targets are analyzed from a unified point of view. Examples include radiation in a finite magnet, bremsstrahlung at double scattering, and bremsstrahlung in an amorphous plate. A generalization of the encountered spectral decomposition property is proposed. The relevance of phenomena of jet-interjet radiation interference and electron time delay in the target is emphasized. Features produced by them in the radiation spectra are discussed.
The polarization effects in the one-meson radiative decay of the polarized $τ$ lepton, $τ^-\toπ^-γν_τ$, are investigated. The inner bremsstrahlung and structural amplitudes are taken into account. The asymmetry of the differential decay width caused by the $τ$ lepton polarization and the Stokes parameters of the emitted photon itself, are calculated depending on the polarization of the decaying $τ$ lepton. The numerical estimation of these physical quantities was done for arbitrary direction of the $τ$ lepton polarization 3-vector in the rest frame. The vector and axial-vector form factors des…
Unusual phenomena in pion production are considered.It is argued that pions may be in a squeezed state having enhanced identical pion correlations. Charge distribution in soft chiral pion bremsstrahlung is shown to be very broad.
We revisit the emissivity from neutrino pair bremsstrahlung in neutron-neutron scattering, nn -> nn nu nubar, which was calculated from the one-pion exchange potential including correlation effects by Friman and Maxwell. Starting from the free-space low-momentum nucleon-nucleon interaction V_{low k}, we include tensor, spin-orbit and second-order medium-induced non-central contributions to the scattering amplitude in neutron matter. We find that the screening of the nucleon-nucleon interaction reduces the emissivity from neutrino bremsstrahlung for densities below nuclear matter density. We di…
It is shown, that the new phenomena of the T-violating photon polarization plane and neutron spin rotation appear under diffraction in a noncentrosymmetrical diffraction grating. The equations describing the T-violating photon scattering by a diffraction grating and neutron interaction with noncentrosymmetrical crystal have been obtained. These phenomena may be used for time-violating interactions investigation.
General properties of the differential cross section and of the polarization observables are derived for the $e^++e^-\to N+\bar N$ reaction, in presence of two--photon exchange. Polarization effects are investigated for longitudinally polarized electron and polarized antinucleon and/or polarized nucleon in the final state. The single--spin asymmetry induced by the transverse polarization of the electron beam is also discussed.
We analyze polarization effects in associative photoproduction of pseudoscalar ($\bar{D}$) charmed mesons in exclusive processes $γ+ N\to Y_c +\bar{D}$, $Y_c=Λ_c^+$, $Σ_c$. Circularly polarized photons induce nonzero polarization of the $Y_c$-hyperon with $x$- and $z$-components (in the reaction plane) and non vanishing asymmetries ${\cal A}_x$ and ${\cal A}_z$ for polarized nucleon target. These polarization observables can be predicted in model-independent way for exclusive $\bar{D}$-production processes in collinear kinematics. The T-even $Y_c$-polarization and asymmetries for non-collinear…
Recently, the so-called relative transverse activity classifier, $R_{\rm T}$, has been proposed as a tool to disentangle the particle production originated from the soft and hard QCD processes in proton-proton (pp) collisions. $R_{\rm T}$ is a useful quantity to study particle production in events with exceptionally large or small activity in the transverse region with respect to the event-averaged mean. Contrary to the expectations, the preliminary results of the ALICE Collaboration indicate that, e.g., the proton-to-pion ratio does not exhibit the characteristic enhancement at intermediate $…
Quantum electrodynamics (qed) is used to derive the differential cross sections measured in the three new experimental internal source ensemble x-ray holographies: bremsstrahlung (BXH), fluorescence (XFH), and multiple-energy (MEXH) x-ray holography. The polarization dependence of the BXH cross section is also obtained. For BXH, we study analytically and numerically the possible effects of the virtual photons and electrons which enter qed calculations in summing over the intermediate states. For the low photon and electron energies used in the current experiments, we show that the virtual inte…
Properties and different representations of the Uehling potential are investigated. Based on these properties and by using our formulas for the Fourier transform of the Uehling potential we have developed the new analytical, logically closed and physically transparent procedure which can be used to evaluate the lowest-order vacuum polarization correction to the cross sections of a number of QED processes, including the Mott electron scattering, bremsstrahlung, creation and/or annihilation of the $(e^{-}, e^{+})-$pair in the field of a heavy Coulomb center, e.g., atomic nucleus.
An expression for the Dalitz plot of the semileptonic decay of a charged kaon, including radiative corrections to order O[απ)(q/M_1)], where q is the four-momentum transfer and M_1 is the mass of the decaying kaon, is obtained. Contributions of both the three- and four-body regions are accounted for. Besides, the emitted muon is considered to be polarized so the analysis is also focused on evaluating the radiative corrections to the longitudinal, transverse, and normal polarization components of the muon. The final formulas, with the triple integration of the bremsstrahlung photon variables re…
In everyday research, it is tacitly assumed that the scattering cross-sections have fixed values for the given particle species, centre-of-mass energy, and particle polarizations. However, this assumption has been called into question after several observations of suppression of high-energy bremsstrahlung. This process will play a major role in experiments at the future Electron-Ion Collider, and we show here how variations of the bremsstrahlung cross-section can be profoundly studied there using the lateral beam displacements. In particular, we predict very strong increase of the observed cro…
The distinction between the charged particle and antiparticle differential cross sections of high-energy bremsstrahlung in the electric field of a heavy atom is investigated. The consideration is based on the quasiclassical approximation to the wave functions in the external field. The charge asymmetry (the ratio of the antisymmetric and symmetric parts of the differential cross section) arises due to the account for the first quasiclassical correction to the differential cross section. All evaluations are performed with the exact account of the atomic field. We consider in detail the charge a…
The features of electromagnetic processes are considered which connected with finite size of space region in which final particles (photon, electron-positron pair) are formed. The longitudinal dimension of the region is known as the formation length. If some external agent is acting on an electron while traveling this distance the emission process can be disrupted. There are different agents: multiple scattering of projectile, polarization of a medium, action of external fields, etc. The theory of radiation under influence of the multiple scattering, the Landau-Pomeranchuk-Migdal (LPM) effect,…
The emission of the hard photon by the initial state is considered. The nucleon polarization and the differential cross sections for some experimental conditions have been calculated. The case of the emission of the collinear (with respect to the direction of the electron beam momentum) photon is considered separately. The differential cross section, the nucleon polarization, the correlation coefficients for both polarized nucleons (provided the electron beam is unpolarized or longitudinally polarized), the transfer polarization from the longitudinally polarized electron beam to the nucleon ha…
We consider radiative corrections to polarization observables in elastic electron-proton scattering, in particular, for the polarization transfer measurements of the proton form factor ratio $μG_E/G_M$. The corrections are of two types: two-photon exchange (TPE) and bremsstrahlung (BS); in the present work we pay special attention to the latter. Assuming small missing energy or missing mass cut-off, the correction can be represented in a model-independent form, with both electron and proton radiation taken into account. Numerical calculations show that the contribution of the proton radiation …
Exclusive light meson production processes possible to be measured at RHIC and LHC accelerators are briefly described. This includes Pomeron and photon induced continuum of pions and kaons as well as $f_0$ and $ρ^0$ resonant production. Next, GenEx, a new Monte Carlo generator recently developed in Cracow, is presented. Its purpose is to generate resonant and non-resonant pion and kaon production and diffractive Bremsstrahlung. Its future development will take into account spin (polarization) effects and simulate corrections due to absorption and re-scattering.
The dependence of the nucleon polarization in the reaction $e^+ + e^- \to N + \bar{N} +π^0 $ over different invariant variables in frame of the non-resonant mechanism, has been derived. The nucleon polarization is expressed in terms of six invariant complex amplitudes, assuming the conservation of the hadron electromagnetic currents and the P-invariance of the hadron electromagnetic interaction. An inclusive experimental setup when the proton (or the antiproton) and the pion are detected in coincidence is considered. Numerical estimations were performed for the so called normal polarization in…
After a short review of the production mechanisms of the light scalars which reveal their nature and indicate their quark structure, we suggest to study the mixing of the isovector a^0_0(980) with the isoscalar f_0(980) in spin effects.
Different phenomenological approaches for Lambda and Lambda-bar polarization in polarized semi-inclusive deep inelastic scattering and electron-positron annihilation at Z^0 pole are considered. Current and future experiments will soon provide accurate enough data to study spin phenomena in these reactions and distinguish between various models.
We compute the dynamical relaxation times for chiral transport phenomena in strongly coupled regime using the AdS/CFT correspondence. These relaxation times can be a useful proxy for the dynamical time scale for achieving equilibrium spin-polarization of quasi-particles in the presence of magnetic field and fluid vorticity. We identify the Kubo relations for these relaxation times and clarify some previous issues regarding time-dependence of the Chiral Vortical Effect. We study the consequences of imposing time-reversal invariance on parity-odd thermal noise fluctuations that are related to ch…
The polarization effects in the one-meson radiative decay of the polarized $τ$ lepton, $τ^-\toπ^-γν_τ$, have been investigated. We present the analytical results for the $t-$distribution of the partial differential widths, which responsible for different polarization phenomena, in the case of the photon energy cut: $ω>X$. These quantities depend on the invariant mass squared $t$ of the pseudoscalar meson and photon and the photon energy cut $X.$ Our analytical formulae, in terms of the weak vector and axial-vector form factors, describing the structure-dependent part of the decay amplitude, ar…
The fragmentation of deuterons into pions emitted forward in the kinematic region forbidden for free nucleon-nucleon collisions is analyzed. It is shown that the inclusion of the non-nucleon degrees of freedom in a deuteron allows to describe the experimental data about inclusive pion spectrum rather satisfactory and improves the description of data concerning the deuteron analyzing power T_{20}. The experimental data show the positive sign and very small values, less than 0.2, of T_{20} what can't be reproduced by the calculations ignoring these degrees of freedom.
We calculate total and differential cross sections for the production of sfermion pairs in photon-photon collisions, including contributions from resolved photons and arbitrary photon polarization. Sfermion production in photon collisions depends only on the sfermion mass and charge. It is thus independent of the details of the SUSY breaking mechanism, but highly sensitive to the sfermion charge. We compare the total cross sections for bremsstrahlung, beamstrahlung, and laser backscattering photons to those in $e^+e^-$ annihilation. We find that the total cross section at a polarized photon co…
Bremsstrahlung of photons from highly relativistic electrons is investigated. The cross section of the processes, which is suppressed due to a multiple scattering of an emitting electron in dense media (LPM effect) and due to photon interaction with electrons of a medium, is calculated with an accuracy up to "next to leading logarithm" and with the Coulomb corrections taken into account. Making allowances for a multiple scattering and a polarization of a medium an analysis of radiation on a target boundary is carried out. The method of consideration of radiation in a thin target under influenc…
We study the renormalization group(RG) evolution of four-quark operators that contribute to the top pair production. In particular, we focus on the cases in which certain observables are \emph{first} induced from the one-loop RG while being absent at tree-level. From the operator mixing pattern, we classify all such RG-induced phenomena and underlying models that can induce them. We then calculate the full one-loop QCD RG evolution as the leading estimator of the effects and address the question of which RG-induced phenomena have largest and observable effects. The answer is related to the col…
Various distributions over the angles of the emitted photon, especially over the azimuthal angle, in the one-meson radiative decay of the polarized $τ$ lepton, $τ^-\toπ^-γν_τ$, have been investigated. In connection with this, the photon phase space is discussed in more detail since in the case of the polarized $τ$ lepton it is not trivial. The decay matrix element contains both the inner bremsstrahlung and the resonance (structural) contributions. The azimuthal dependence of some observables have been calculated. They are the asymmetry of the differential decay width caused by the $τ$ lepton p…
The study of the longitudinal polarization of Lambda and Lambda-bar hyperons produced in polarized deep inelastic scattering, neutrino scattering, and in Z0 decays allows to access the spin dynamics of the quark fragmentation process. Different phenomenological spin transfer mechanisms are considered and predictions for the Lambda and Lambda-bar longitudinal polarization in various processes using unpolarized and polarized targets are made. Current and future semi-inclusive deep inelastic scattering experiments will provide soon accurate enough data to study these phenomena and distinguish bet…
In the standard model the mass of elementary particles is considered as a dynamical property emerging from their interaction with the Higgs field. We show that this assumption implies peculiar deviations from the law of universal gravitation in its distance and mass dependence, as well as from the superposition principle. The experimental observation of the predicted deviations from the law of universal gravitation seems out of reach. However, we argue that a new class of experiments aimed at studying the influence of surrounding masses on the gravitational force - similar to the ones performe…
Spin polarized states in nuclear matter with an effective nucleon-nucleon interaction are studied for a wide range of isospin asymmetries and densities. Based on a Fermi liquid theory, it is shown that there are a few possible scenarios of spin ordered phase transitions: (a) nuclear matter undergoes at some critical density a phase transition to a spin polarized state with the oppositely directed spins of neutrons and protons (Skyrme SLy4 and Gogny D1S interactions); (b) at some critical density, a spin polarized state with the like-directed neutron and proton spins appears (Skyrme SkI5 intera…
The $K^+$ and $K^0$ meson mass difference induces the mixing of the $a^0_0(980)$ and $f_0(980)$ resonances, the amplitude of which, between the $K^+K^-$ and $K^0\bar K^0$ thresholds, is large in magnitude, of the order of $ m_{K}\sqrt{m^2_{K^0}-m^2_{K^+}}\approx\sqrtαm^2_K$, and possesses the phase sharply varying by about 90$^\circ$. We suggest performing the polarized target experiments on the reaction $π^-p\toηπ^0n$ at high energy in which the fact of the existence of $a^0_0(980)-f_0(980)$ mixing can be unambiguously and very easily established through the presence of a strong jump in the a…
The fragmentation of deuterons into pions emitted forward in the kinematic region forbidden for free nucleon-nucleon collisions is analyzed. The inclusive relativistic invariant spectrum of pions and the tensor analyzing power T_{20} are investigated within the framework of an impulse approximation using different kinds of the deuteron wave function. The influence of P-wave inclusion in the deuteron wave function is studied, too. The invariant spectrum is shown to be more sensitive to the amplitude of the $NN \to πX$ process than the tensor analyzing power T_{20}. It is shown that the inclusio…
Relativistic heavy-ion collisions create hot quark-gluon plasma as well as very strong electromagnetic (EM) and fluid vortical fields. The strong EM field and vorticity can induce intriguing macroscopic quantum phenomena such as chiral magnetic, chiral separation, chiral electric separation, and chiral vortical effects as well as the spin polarization of hadrons. These phenomena provide us with experimentally feasible means to study the nontrivial topological sector of quantum chromodynamics, the possible parity violation of strong interaction at high temperature, and the subatomic spintronics…
We compute the flux of axions from Active Galactic Nuclei (AGN). Axions can be produced in the accretion disk by the Compton, Bremsstrahlung and Primakoff processes. We find that the axion luminosity due to these processes is negligible in comparison to the photon luminosity from AGNs. We also compute the luminosity of a hypothetical pseudoscalar, with very small mass, from the AGN atmosphere due to the phenomenon of pseudoscalar-photon mixing in background magnetic field. In this case we find that for some parameter ranges, the pseudoscalar flux can exceed that of photons. We comment on the i…
