Photon damping caused by electron-positron pair production in a strong magnetic field

Damping of an electromagnetic wave in a strong magnetic field is analyzed in the kinematic region near the threshold of electron-positron pair production. Damping of the electromagnetic field is shown to be noticeably nonexponential in this region. The resulting width of the photon γ→e ⁺ e ^? decay is considerably smaller than previously known results.     

Nonresonant muon pair production in electron-positron annihilation in the field of light wave

In the frame of the Born approximation it was theoretically investigated nonresonant muon pair production in e ⁺ e ⁻ collision in the field of elliptically polarized electromagnetic wave in the general relativistic case. It was analyzed in detail the reaction kinematics. It was derived the expressions for the amplitude and the cross section of the nonresonant muon pair production in e ⁺ e ⁻ annihilation in the moderately strong field. It was demonstrated that the partial cross-section is factorized as a product of the cross section of the muon pair production from e ⁺ e ⁻ pair in the absence of the external field and the probability of emission and absorption of photons from the wave. Original Text ? Astro, Ltd., 2009. The article is published in the original.     

Gluino pair production in electron-positron annihilation

We summarize the effects of some unknown supersymmetry breaking mechanism by the addition to the super-QCD lagrangian of explicit, and different, mass terms for the scalar superpartners of quarks and antiquarks. Allowing also a possible Majorana mass for the gluino, we then calculate cross sections for e⁺e^? → two gluinos, a process which may be observable if the gluino is sufficiently long-lived.     

The Schwinger effect and possibilities for its observation using optical and X-ray lasers

The probability W of e ⁺ e ^? pair production from a vacuum in an intense variable electric field generated with powerful optical or X-ray lasers is calculated. Two characteristic ranges are considered: γ ? 1 and γ ? 1, where γ is the adiabaticity parameter. The probability W is shown to increase sharply with γ (at a fixed field strength F). The dependence of W and the momentum spectrum of electrons and positrons on the laser pulse shape is discussed in detail. Numerical calculations were performed for a laser pulse with a Gaussian envelope and for some pulsed fields.     

Seed and vacuum pair production in strong laser field

Researches on the electron-positron pair production in the presence of the intense laser field are reviewed, motivated by the theoretical importance of the nonperturbative QED problem and the worldwide development of high power laser facilities. According to the distinct experimental requirements and theoretical methods, two types of pair production are elaborated, which are, respectively, pair production in the combination of a seed particle and the strong laser, and vacuum pair production without a seed particle. The origin of the nonperturbative problem caused by the strong field is analyzed. The main ideas, realisation, achievements, validity, challenges and bottleneck problems of the nonperturbative methods developed for each type of the pair production problem are discussed.     

The diffraction mechanism of electron-positron pair photoproduction

We examine a mechanism of electron-positron pair photoproduction near a giant resonance. The mechanism is based on the possibility of photons being absorbed by nuclei. Our calculations set the cross section of this process at roughly 10⁻³⁰ cm². We also discuss the feasibility of observing the effect. Zh. éksp. Teor. Fiz. 112, 1959–1965 (December 1997)     

Laser field absorption in self-generated electron-positron pair plasma

Recently, much attention has been attracted to the problem of limitations on the attainable intensity of high power lasers [A.?M. Fedotov et al., Phys. Rev. Lett. 105, 080402 (2010)]. The laser energy can be absorbed by electron-positron pair plasma produced from a seed by a strong laser field via the development of the electromagnetic cascades. The numerical model for a self-consistent study of electron-positron pair plasma dynamics is developed. Strong absorption of the laser energy in self-generated overdense electron-positron pair plasma is demonstrated. It is shown that the absorption becomes important for a not extremely high laser intensity I ～ 10(24) W/cm(2) achievable in the near future.     

Double- and multi-photon pair production and electron-positron entanglement

We investigate entanglement of electrons and positrons produced via absorption by a vacuum of two or several photons from two external electromagnetic waves. The waves are modelled by finite-length focused pulses. Structures of the arising electron and positron wave packets are investigated in the momentum and coordinate representations. Conditional and unconditional widths of these wave packets, as well as the Schmidt number K are found, and they are used to evaluate the degree of entanglement. The conditions are found when entanglement is large. It is shown that the highest entanglement can be reached at nonrelativistic energies of electrons and positrons. Possibilities of observing the entanglement effects in experiments on pair production are discussed.     

Resonance mechanism of the production of electron-positron pairs in a strong magnetic field

The Compton-like process γe ^± → e ^± e ⁺ e ^? involving the production of an electron-positron pair in the interaction of an ultrarelativistic electron with a soft x-ray photon in the vicinity of the polar cap of a magnetar is considered. It is shown that the amplitude for this reaction has a resonance character. A simple analytic expression is obtained for the electron-absorption coefficient. Possible astrophysical implications of the resonance process γe ^± → e ^± e ⁺ e ^? are discussed.     

Formation of an electron-positron pair by two photons in a nuclear field

The Born approximation of perturbation theory is used to analyze the formation of an electron-positron pair by two parallel photons in the Coulomb field of an atomic nucleus.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 62–66, February, 1978.     

Schwinger mechanism for gluon-pair production in the presence of arbitrary time-dependent chromo-electric field

We study the Schwinger mechanism for gluon-pair production in the presence of an arbitrary time-dependent chromo-electric background field E ^a (t) with arbitrary color index a=1,2,…,8 in SU(3) by directly evaluating the path integral. We obtain an exact expression for the probability of non-perturbative gluon-pair production per unit time per unit volume and per unit transverse momentum, , from arbitrary E ^a (t). We show that the tadpole (or single-gluon) effective action does not contribute to the non-perturbative gluon-pair production rate, . We find that the exact result for non-perturbative gluon-pair production is independent of all the time derivatives , where n=1,2,…,∞, and that it has the same functional dependence on the two Casimir invariants, [E ^a (t)E ^a (t)] and [d _abc E ^a (t)E ^b (t)E ^c (t)]², as the constant chromo-electric field E ^a result with the replacement: E ^a →E ^a (t). This result relies crucially on the validity of the shift conjecture, which has not yet been established. This result may be relevant to the study of the production of a non-perturbative quark–gluon plasma at RHIC and LHC.     

Mechanism of electron-positron pair production by high-energy photons in a single crystal

A mechanism of pair production by photons in an electric field of the axes (planes) of a single crystal is discussed. Simple expressions for the process probability and spectral distribution at κ?1 are presented. An analysis of conditions to observe the effect is made.     

Radiative muon pair production in high-energy electron-positron annihilation process

The lowest order radiative correction to the differential cross section of process of muon pair production with the emission of a hard photon at high energy electron-positron annihilation are calculated. Taking into account the emission of additional soft and hard photon, the cross section can be put in the form of the Drell-Yan process in leading logarithmical approximation. Applying the crossing transformation, we obtain the cross section of the radiative electron-muon high-energy scattering process. Virtual and soft photon emission contributions of the nonleading form are tabulated for several typical kinematical points. The limit of the small invariant mass of a muon pair is in agreement with our previous analysis.     

Production of an electron-positron pair and a photon from the vacuum in a radiation-dominated universe

A study is made of the production of an electron-positron pair and a photon from the vacuum in a Robertson-Walker space with metric ds²=a²()(d²–dx²–dy²–dx²). In Minkowski space, this process is forbidden by the conservation laws. The differential probability of the process is calculated, and its behavior in various kinematic regions is investigated. The probability of the process is estimated numerically for times close to the electron Compton time, and the probability of production of a pair and photon from the vacuum is compared with the probability of pair production in the absence of radiative coupling.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 61–66, February, 1991.     

Enhanced electron–positron pair production by frequency chirping in one-and two-color laser pulse fields

Enhanced electron–positron pair production by frequency chirping in one- and two-color laser pulse fields is investigated by solving the quantum Vlasov equation. A small frequency chirp shifts the momentum spectrum along the momentum axis. The positive and negative frequency chirp parameters play the same role in increasing the pair number density. The sign change of the frequency chirp parameter at the moment t = 0 leads the pulse shape and momentum spectrum to be symmetric, and the number density to be increased. The number density of produced pairs in the two-color pulse field is much higher than that in the one-color pulse field and the larger frequency chirp pulse field dominates more strongly. In the two-color pulse fields, the relation between the frequency ratio of two colors and the number density is not sensitive to the parameters of small frequency chirp added in either a low frequency strong field or a high frequency weak field but sensitive to the parameters of large frequency chirp added in a high frequency weak field.     

关于J/ψ→Gb+γ和J/ψ→e+ē过程

基于J/ψ辐射产生胶球态Gb和湮没为e+ē对两过程的中间态和末态都不涉及任何夸克强子而只与强作用的真空性质密切相关这一特性，从另一种角度讨论了这两个过程.利用高能强作用软过程中修改后的pomeron场论模型和相关的最大非微扰强作用反应假定，并考虑到轻的和重的组分夸克在结构上的差异而在模型参数中作出相应的变更后，提出了这两个过程的另一种物理机制，计算了它们的衰变宽度，定出了胶球态与非微扰胶子间的耦合数值，并就此进行了简单的讨论. 关键词： J/ψ衰变 pomeron 非微扰     

关于J/ψ→Gb+γ和J/ψ→e+(-e)过程

基于J/ψ辐射产生胶球态Gb和湮没为e-e对两过程的中间态和末态都不涉及任何夸克强子而只与强作用的真空性质密切相关这一特性,从另一种角度讨论了这两个过程.利用高能强作用软过程中修改后的pomeron场论模型和相关的最大非微扰强作用反应假定,并考虑到轻的和重的组分夸克在结构上的差异而在模型参数中作出相应的变更后,提出了这两个过程的另一种物理机制,计算了它们的衰变宽度,定出了胶球态与非微扰胶子间的耦合数值,并就此进行了简单的讨论.