Electron-positron pair production by photons in nonuniform strong fields

A probability of electron-positron pair production by photons in strong nonuniform fields is derived by applying a model trajectory method in the frame of a semiclassical approach. In addition to the well known invariant field parameter chi, a new invariant parameter nu is introduced to characterize the nonuniformity of the field. For nu>1, the obtained expression is reduced to the uniform-field approximation while it approaches the Bethe-Heitler formula for nu<1. The pair production is predicted for relatively weak external fields where the uniform-field approximation gives no effect. The theory agrees well with the experimental results of crystal-assisted pair production.     

超强场下的正负电子对产生

随着现代强激光技术的迅速发展,激光场强已经进入到了强相对论区域,并正在向产生正负电子对的施温格临界场强逼近。文章着重介绍了超强场下真空失稳产生正负电子对的问题,从历史及其发展的脉络中梳理出有重要价值的研究方法和有趣的研究成果,对目前的研究现状做了综述,并对未来的研究进行展望。     

Electron-positron pair formation by two identical photons in the nuclear field

The effect of electron-positron pair formation by two identical photons in the Coulomb field of an atomic nucleus is considered in the Born approximation of perturbation theory.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 20–23, February, 1977.     

Electron-positron pair production in the low-density approximation

Electron–positron pair creation is studied in the low-density approximation by solving the quantum Vlasov equation exactly and the mapping equation approximately. The simpler mapping equation is an approximate treatment of the quantum Vlasov equation in which the continuous external field is regarded as a series of delta kicks. Our study indicates that this new treatment is appropriate because the results of the two methods are in good agreement with each other. However, as the period number increases, interference and a complicated structure in the momentum distribution are observed. Furthermore, we also obtain the square power law relation of the number density to the applied electric field strength.     

Electron-positron pair and photon generation from vacuum in a de sitter space

Electron-positron pair and photon generation from vacuum is considered for a de Sitter space. The amplitude is calculated in the lowest order of perturbation theory with respect to the radiation interaction. The initial and final vacuum states of the quantized spinor field are taken as those of an adiabatic Bunch-Davis vacuum. The amplitude is shown to be zero, i.e., an adiabatic vacuum in a de Sitter space is stable with respect to radiation. Biya Technological Institute, Polzunov Altai State Technological University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 85–89, October, 1998.     

Electron-positron pair production in a strong asymmetric laser electric field

By solving the quantum Vlasov equation, electron positron pair production in a strong electric field with asymmetric laser pulses has been investigated. We consider three different situations of subcycle, cycle and supercycle laser pulses. It is found that in asymmetric laser pulse field, i.e.. when the pulse length of one rising or falling side is fixed while the pulse length of the other side is changed, the pair production rate and mnnber density can be significantly modified comparable to symmetric situation. For each ca,se of these three different cycle pulses, when one side pulse length is constant and the other side pulse length becomes shorter, i.e., the whole pulse is compressed, the more pairs can be produced than that in tile vice versa case, i.e., the whole pulse is elongated. In compressed pulse case there exists an optimum pulse length ratio of asylnmetric pulse lengths which makes the pair number density maximunn. Moreover, the created maximum pair number density by subcycle pulse is larger than that by cycle or/and supercycle pulse. In elongated pulse case, however, only for supercycle laser pulse the created pairs is enhanced and there exists also an optimum asymmetric pulse length ratio that maximizes the pair number density. On the other hand. surprisingly, in both cases of subcycle and cycle elongated laser pulses, the pair number density is monotonically decreasing as the asymmetry of pulse increases.     

Electron-positron pair creation by photons in an aligned single crystal: Comparison of theory with experiment

The creation of electron-positron pairs by 50–110 GeV photons directed along the 〈110〉 axis of a cooled crystal is considered. The results obtained are compared with a very recent experiment performed in CERN. Radiation from electrons is also discussed.     

Electron-positron pair production by collisions of non-relativistic charged particles

The cross-section for (e ⁺,e ^?)-pair production in collisions of non-relativistic charged particles has been calculated to lowest order in the fine structure constant and leading power of the relative velocity of the colliding particles. Thus the deflection of colliding particles is included in one-photon-exchange approximation, while the Coulomb distortion of the (e ⁺,e ^?)-pair is omitted. We have laid particular emphasis on current conservation. The previously neglected contribution of the spatial part of the current turns out to be dominant.     

Electron-positron pair production as a probe of chiral symmetry in a hot QCD plasma

Chiral symmetry in the high-temperature plasma phase of QCD is consistent with at least three qualitatively different quark dispersion relations. The rate for $\text{q}\text{q}\text{→}\text{e}{}^{\mathrm{+}}\text{e}{}^{\mathrm{?}}$, with zero total momentum of the e⁺e^? pair in the plasma rest frame is direct measure of the quark dispersion relation. For the three plausible dispersion relations the rates differ by orders of magnitude when the e⁺e^? invariant mass M < 2T.     

Observing quantum vacuum lensing in a neutron star binary system

In this Letter we study the propagation of light in the neighborhood of magnetized neutron stars. Because of the optical properties of quantum vacuum in the presence of a magnetic field, the light emitted by background astronomical objects is deviated, giving rise to a phenomenon of the same kind as the gravitational one. We give a quantitative estimation of this effect, and we discuss the possibility of its observation. We show that this effect could be detected by monitoring the evolution of the recently discovered double neutron star system J0737-3039.     

Electron-positron pair production by an electron in a magnetic field near the process threshold

The electron-positron pair production by an electron in a strong magnetic field near the process threshold is considered. The process is shown to be more probable if the spin of the initial electron is oriented along the field. In this case, the probability of the process is 10¹³ s⁻¹ when the magnetic field strength is H = 4 × 10¹² G.     

Electron-positron pair generation by a neutrino in a magnetic field

The probability of generation of an e⁺ e^– pair by a neutrino moving in a magnetic field is calculated in the low energy approximation of the Weinberg-Salam model with consideration of electron and positron spin states.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 30–34, August, 1983.The authors thank A. A. Sokolov forhis kind evaluation of the study.     

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.     

QCD phase transition in rotating neutron star,neutrino beaming and gamma-ray bursters

We have studied the emission of neutrinos from a rotating hybrid star. We find that the emission is predominantly confined to a very small angle, provided the core of the star is in a mixed phase of quarks and hadrons and the size of such a mixed phase is small. Annihilation of neutrinos to produce gamma rays has been discussed. The estimated duration of the burst is found to be within the observational range.     

Electron-positron pair formation in the field of a bichromatic plane electromagnetic wave

On the basis of the accurate solution of the Dirac equation for an electron in the field of a bichromatic plane wave consisting of two monochromatic waves propagating in the same direction, the probability of formation of an e⁺e^– pair by a quantum in the wave field is calculated. The cases of small and large intensities of the wave components are considered, together with the transition in the limit to a constant field.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 46–53, February, 1977.The authors thank A. A. Sokolov for his constant interest in the work and discussion of the results.     

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.     

强场下真空中粒子对产生的研究进展

随着激光技术的飞快发展,激光强度不断提高,超强外场下真空中正负电子对产生的过程,即能量向质量转化过程,已经成为一个研究热点。主要综述了近几年量子Vlasov方程方法和计算量子场论(数值求解Dirac方程)方法在研究强场下真空中正负电子对产生方面的进展,分别介绍了空间均匀场和空间不均匀场下的粒子对产生的情况。第一种情况主要介绍双脉冲结构振荡电场中电子-正电子对的产生、强双频振荡电场中非微扰电子-正电子对的产生、频率调制的激光场中电子-正电子对的产生和Dirac真空对啁啾外场的快速分辨。第二种情况主要介绍优化空间局域电场提高粒子对的产生率、多个势阱-垒结构的振荡场对粒子对产生的增强、振荡 Sauter 电势中正负电子对产生的问题、操纵Dirac真空以控制其在场诱导下的衰变、作为信息传输介质的Dirac真空还有正负电子对产生中的相干和非相干啁啾机制的转变。