Quantum theory of transition radiation and transition pair creation

A theory of the transition radiation and the transition pair creation is developed in the frame of QED. The spectral-angular distributions of probability of the transition radiation and of the transition pair creation are found. The total energy losses of an electron and the total probability of pair creation by a photon are calculated and analyzed. Features of radiation and pair creation processes in a superdense medium (typical for white dwarfs) are discussed.     

Radiation,pair creation,and semiclassical QED in crystals

Abstract

The surface potential on pure and doped sodium chloride single crystals fits conventional defect theory, but the potential on grain boundaries in bicrystals is difficult to explain. The electrical width of the grain boundary is also an uncertain quantity that needs further investigation.     

Electroproduction of electron-positron pair in oriented crystal at high energy

The process of electroproduction of the electron-positron pair by high energy electron in an oriented single crystal is investigated. Two contributions are considered: the direct (one-step) process via the virtual intermediate photon and the cascade (two-step) process when the electron emits the real photon moving in the field of axis and afterwards the photon converts into the pair. The spectrum of created positron (electron) is found. It is shown that the probability of the process is strongly enhanced comparing with the corresponding amorphous medium.     

Recombination-assisted creation of cation excitons and cross-luminescence quenching in CsCl crystals at high excitation densities

At high excitation densities, recombination-assisted creation of cation excitons, which transfer energy efficiently to the anion sublattice to initiate the luminescence of anion excitons and impurity centers, has been observed in CsCl crystals. At the same time, the creation of cation excitons competes with the electron recombination with cation holes and quenches the cross-luminescence. The intensity ratio of the cross-luminescence to exciton-impurity luminescence is different for crystal irradiation with γ rays and heavy particles.     

Electroweak corrections to muon pair production in electron-positron annihilation at high energy

The lowest-order radiative corrections to the reaction e⁺ + e⁻ → μ⁺ + μ⁻ are analyzed in the standard SU(2) × U(1) electroweak theory. The virtual corrections are calculated in the on-shell renormalization scheme. The masses of the recently discovered Z-boson and W-boson are used to fix the weak coupling constants. The decay width of the Z-boson is also taken into account. By including the cross section of hard photon emission, various kinds of distribution are obtained both analytically and numerically. The magnitude of the effective axial vector coupling is confirmed to be quite different from that previously taken in the calculations within QED. This difference, which is due to the genuine electroweak corrections, reaches about 10% in angular distribution at the energy around the Z-boson mass, even if the reasonable effect of a hard photon is included.     

Dynamic chaos phenomenon and coherent radiation accompanying high energy particle motion through crystals

Abstract

A crystal has a regular structure, therefore every motion in such a structure seems to be regular. However, it is not actually so and even in perfect crystals the particle motion may be either regular or chaotic. Everything depends on the number of integrals of motion determining a particle trajectory.

The character of particle motion in a crystal, i.e. its regularity or chaoticity, affects many physical processes accompanying the particle motion through a crystal. In this paper we shall consider the effect of dynamic chaos on the coherent radiation of fast particles in a crystal.

We also consider the validity conditions of coherent radiation theory results, the role of the second and higher Born approximations in the radiation theory of fast particles in crystals, the continuous string approximation in this theory, the coherent radiation in the model of random strings, and the multiple scattering effect on the coherent radiation.     

A novel theory of radiation damage at high doses

Abstract

The deviations of radiation damage (in the case of metals usually monitored by the residual electrical resistivity) from proportionality to the irradiation dose have so far been analysed almost exclusively in terms of extensions of models originally developed for small doses. The present theory considers the opposite limit, i. e. the quasi-saturated state. It is argued that at high doses the Lück-Sizmann effect may result in a self-organization of clusters of vacancies and self-intersititials, forming a heterogeneous froth. Possible structures of this froth and its effect on the electrical resistivity of metals are discussed. The model is shown to account for the dependence of the “saturation resistivity” on the nature of the irradiation as well as for several other hitherto poorly explained observations. Among them are the electrical-resistivity variation induced by high-dose irradiation with heavy ions, the amorphization of certain alloys by high-dose electron irradiation, and the occurrence of ordered arrays of stacking-fault tetrahedra after in-situ irradiations in high-voltage electron microscopes.     

Angular correlations in pair creation

We present the Monte Carlo analysis of angular correlations in electron-positron pair production by the laser field-heavy ions impact process. It is shown that, for linearly polarized laser fields, pairs are created mainly in the plane spanned by the polarization vector and the laser photon momentum, and that the angular distribution of created electrons and positrons is anticorrelated.     

Non-linear pair production in scattering of photons on ultra-short laser pulses at high energy

We consider scattering of a photon on a short intense laser pulse at high energy. We argue that for ultra-short laser pulses the interaction is coherent over the entire length of the pulse. At low pulse intensity I the total cross section for electron–positron pair production is proportional to I  . However, at pulse intensities higher than the characteristic value Is$I_s$, the total cross section saturates – it becomes proportional to the logarithm of intensity. This non-linear effect is due to multi-photon interactions. We derive the total cross section for pair production at high energies by resuming the multi-photon amplitudes to all orders in intensity. We calculate the saturation intensity Is$I_s$ and show that it is significantly lower than the Schwinger's critical value. We discuss possible experimental tests.     

Developments in high energy theory

This non-technical review article is aimed at readers with some physics background, including beginning research students. It provides a panoramic view of the main theoretical developments in high energy physics since its inception more than half a century ago, a period in which experiments have spanned an enormous range of energies, theories have been developed leading up to the Standard Model, and proposals — including the radical paradigm of String Theory — have been made to go beyond the Standard Model. The list of references provided here is not intended to properly credit all original work but rather to supply the reader with a few pointers to the literature, specifically highlighting work done by Indian authors.     

Parity violation in high energy Lepton pair production and QCD

We use the quark-parton model with perturbative QCD corrections in the Weinberg-Salam theory to calculate a parity-violating asymmetry in inclusive lepton pair production. We estimate the asymmetry proportional to the triple correlation $\text{〈}\text{P·l}{}^{\mathrm{+}}\text{×}\text{l}{}^{\mathrm{?}}\text{〉}$ of the lepton momenta $\text{l}{}^{\mathrm{+}}\text{and}\text{l}{}^{\mathrm{?}}$ and the incident hadron momentum $\text{P}$. We find that a nonzero asymmetry requires inclusion of nonperturbative effects.     

Muon pair production in very high energy nucleus-nucleus collisions

Characteristics of muon pair production in very high energy nucleus-nucleus collisions are discussed. Particular attention is given to comparing the rate of muon pairs produced from thermalized quark-gluon matter to that of pairs produced via the usual Drell-Yan mechanism. The thermal rate is at least of the same order of magnitude as the direct Drell-Yan rate and will certainly dominate whenx _F for the pair approaches 1. Beyondx _F =1 the thermal rate is also substantial. This region is particularly easily accessible in fixed target experiments.     

Radiation effects in monopole pair creation

Considering the infrared problem in monopole pair creation, we find that the corresponding radiation effects yield an enormous damping of the cross section. This result has relevance for the problem of magnetic preon confinement and possibly monopole creation in the early universe.     

Schwinger pair creation in multilayer graphene

The low energy effective field model for the multilayer graphene (at ABC stacking) in external Electric field is considered. The Schwinger pair creation rate and the vacuum persistence probability are calculated using the semiclassical approach.     

Electron-positron pair creation and Oleinik resonances

We consider the process of electron-positron pair creation by an impact of ultra-intense laser beam on a highly relativistic nucleus, with an exact account for its finite mass. It is shown that the probability rates of pair production increase tremendously due to the nuclear recoil. Numerical calculations also show the existence of very narrow resonances in differential probability rates of pair production, which are recognized to be Oleinik resonances, as they originate from poles of the photon propagator. Using our exact treatment of the colliding nucleus, we analyze also the effect of dressing it by the laser field on the process of pair creation.     

Quasiclassical theory of a charged Bose gas

The static linear response of a charged Bose gas in the presence of a magnetic field is studied in a “quasiclassical” model previously proposed for an electron gas. The Bose gas is shown to exhibit different screening behavior. The relevance of the study of a charged Bose gas in relation to understanding the properties of systems like neutron star is discussed.