SIMULTANEOUS CREATION OF ELECTRON–POSITRON PAIRS AND PHOTONS IN ROBERTSON–WALKER UNIVERSES WITH STATICALLY BOUNDED EXPANSION

1992 ◽  
Vol 07 (12) ◽  
pp. 2695-2712 ◽  
Author(s):  
K.-H. LOTZE
Keyword(s):  
Quantum Electrodynamics ◽  
Particle Creation ◽  
Conformally Flat ◽  
Coupling Constant ◽  
Zeroth Order ◽  
Attenuation Effect ◽  
Interacting Particle ◽  
Electron Positron ◽  
Electrons And Positrons ◽  
Bounded Expansion

We present, based upon quantum electrodynamics in Robertson–Walker flat universes, a thorough analysis of the creation of mutually interacting electron–positron pairs and photons from vacuum. Therefore we discuss at least qualitatively all processes contributing to the number densities of created particles up to the second order in the coupling constant. For two particular expansion laws with Minkowskian in respectively in and out regions, we obtain exact solutions to the Dirac equation and investigate in detail the process of simultaneous creation of electron–positron pairs and photons and the related attenuation effect for fermionic particles. This is done for electrons and positrons which have nonrelativistic momenta at Compton time in rapidly expanding universes. The results are compared with the zeroth-order creation of electron–positron pairs. Despite being smaller by a factor of roughly [Formula: see text], the interacting-particle creation is important mainly as a source of photons even in conformally flat universes.

scholarly journals QED in the clothed-particle representation: a fresh look at positronium properties treatment

2020 ◽  
Author(s):  
Yan Kostylenko ◽  
Adam Arslanaliev ◽  
Aleksandr V. Shebeko
Keyword(s):  
Decay Rate ◽  
Distinctive Feature ◽  
Ground State ◽  
Quantum Electrodynamics ◽  
Bound States ◽  
Analytical Expression ◽  
New Family ◽  
Electron Positron ◽  
Electrons And Positrons

We have extended our previous applications of the method of unitary clothing transformations (UCTs) in mesodynamics [1,2] to quantum electrodynamics (QED) [3,4]. An analytical expression for the QED Hamiltonian in the clothed-particle representation (CPR) has been derived. Its distinctive feature is the appearance of a new family of the Hermitian and energy independent interaction operators built up in the e^2e2-order for the clothed electrons and positrons instead the primary canonical interaction between electromagnetic and electron-positron fields. The problem of describing the bound states in QED in case of the positronium system has been considered. The first correction to the energy of the ground state of the para-positronium and its decay rate to two photons has been calculated by using the new interaction operators.

scholarly journals Dominance of γ-γ electron-positron pair creation in a plasma driven by high-intensity lasers

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Yutong He ◽  
Thomas G. Blackburn ◽  
Toma Toncian ◽  
Alexey V. Arefiev
Keyword(s):  
High Intensity ◽  
Quantum Electrodynamics ◽  
Linear Process ◽  
Pair Creation ◽  
Jet Formation ◽  
Beam Laser ◽  
Electron Positron ◽  
Electrons And Positrons ◽  
Laser Facility ◽  
Basic Prediction

AbstractCreation of electrons and positrons from light alone is a basic prediction of quantum electrodynamics, but yet to be observed. Our simulations show that the required conditions are achievable using a high-intensity two-beam laser facility and an advanced target design. Dual laser irradiation of a structured target produces high-density γ rays that then create > 108 positrons at intensities of 2 × 1022 Wcm−2. The unique feature of this setup is that the pair creation is primarily driven by the linear Breit-Wheeler process (γγ → e+e−), which dominates over the nonlinear Breit-Wheeler and Bethe-Heitler processes. The favorable scaling with laser intensity of the linear process prompts reconsideration of its neglect in simulation studies and also permits positron jet formation at experimentally feasible intensities. Simulations show that the positrons, confined by a quasistatic plasma magnetic field, may be accelerated by the lasers to energies >200 MeV.

Vacuum polarization and particle creation in the presence of a potential step

2016 ◽  
Vol 31 (02n03) ◽  
pp. 1641031 ◽  
Author(s):  
S. P. Gavrilov ◽  
D. M. Gitman
Keyword(s):  
Electric Potential ◽  
Canonical Quantization ◽  
Particle Creation ◽  
Pair Creation ◽  
Dirac Field ◽  
Potential Step ◽  
Electron Positron ◽  
Physical Impact ◽  
Particle Interpretation ◽  
Electron Positron Pair

We consider QED with strong external backgrounds that are concentrated in restricted space areas. The latter backgrounds represent a kind of spatial x-electric potential steps for charged particles. They can create particles from the vacuum, the Klein paradox being closely related to this process. We describe a canonical quantization of the Dirac field with x-electric potential step in terms of adequate in- and out-creation and annihilation operators that allow one to have consistent particle interpretation of the physical system under consideration and develop a nonperturbative (in the external field) technics to calculate scattering, reflection, and electron-positron pair creation. We resume the physical impact of this development.

scholarly journals Driving positron beam acceleration with coherent transition radiation

2020 ◽  
Vol 3 (1) ◽  
Author(s):  
Zhangli Xu ◽  
Longqing Yi ◽  
Baifei Shen ◽  
Jiancai Xu ◽  
Liangliang Ji ◽  
...  
Keyword(s):  
Longitudinal Magnetic Field ◽  
Transition Radiation ◽  
Positron Beam ◽  
Acceleration Process ◽  
Wakefield Acceleration ◽  
Electron Positron ◽  
Electrons And Positrons ◽  
Energy Peak ◽  
Coherent Transition Radiation ◽  
Plasma Wakefield

Abstract Positron acceleration in plasma wakefield faces significant challenges, as the positron beam must be pre-generated and precisely coupled into the wakefield and, most critically, suffers from defocusing issues. Here we propose a scheme that utilizes laser-driven electrons to produce, inject, and accelerate positrons in a single setup. The high-charge electron beam from wakefield acceleration creates copious electron–positron pairs via the Bethe–Heitler process, followed by enormous coherent transition radiation due to the electrons’ exiting from the metallic foil. Simulation results show that the coherent transition radiation field reaches up to tens of GV m−1, which captures and accelerates the positrons to cut-off energy of 1.5 GeV with energy peak of 500 MeV (energy spread ~ 24.3%). An external longitudinal magnetic field of 30 T is also applied to guide the electrons and positrons during the acceleration process. This proposed method offers a promising way to obtain GeV fast positron sources.

scholarly journals Electron-positron pair production observed from laser-induced processes in ultra-dense deuterium D(-1)

2014 ◽  
Vol 32 (4) ◽  
pp. 537-548 ◽  
Author(s):  
Frans Olofson ◽  
Leif Holmlid
Keyword(s):  
Pair Production ◽  
Time Of Flight ◽  
Forward Direction ◽  
Metal Plate ◽  
Negative Bias ◽  
Lepton Pairs ◽  
Rapid Variation ◽  
Electron Positron ◽  
Electrons And Positrons ◽  
Time Variations

AbstractLaser-induced fusion in ultra-dense deuterium D(-1) is reported in several studies from our group, using ns- and ps-pulsed lasers. The ejection of ultra-dense hydrogen particles with thermal distributions and energy up to 20 MeV u−1 was studied previously by time-of-flight measurements. The investigations of the new processes continue now by studying the interaction of these particles with metal surfaces. In the present experiments, such particles penetrate in two steps through 1 mm of metal and reach three levels of collectors at distances up to 1 m. Only the fastest particles penetrate and move to the next level. The thermal time-of-flight distributions together with tests with strong magnetic fields exclude electrons as the particles observed. The sign of the signals to the metal collectors depends on the bias (negative bias gives positive signal and conversely) while the time variations of the signals for positive and negative bias are similar. The rapid variation of the signals indicates electrons and positrons ejected from the collectors, thus lepton-pair production. An increase in bias up to ± 400 V increases the peak signal up to 1 A with no observed limiting. A thick metal plate removes slow particles and most gamma photons. The number of lepton-pairs produced is > 4 × 1012 sr−1 in the forward direction per laser shot.

scholarly journals Ion acoustic quasi-soliton in an electron-positron-ion plasma with superthermal electrons and positrons

Open Physics ◽  
2018 ◽  
Vol 16 (1) ◽  
pp. 563-567 ◽  
Author(s):  
Jianyong Wang ◽  
Ying Zeng ◽  
Zufeng Liang ◽  
Yani Xu ◽  
Yuanxiang Zhang
Keyword(s):  
Acoustic Waves ◽  
Vries Equation ◽  
Reductive Perturbation Method ◽  
Superthermal Electrons ◽  
Ion Plasma ◽  
Electron Positron ◽  
Electrons And Positrons ◽  
Ion Acoustic ◽  
De Vries ◽  
Superthermal Electrons And Positrons

Abstract In this work, we are concerned with the ion acoustic quasi-soliton in an electron-positron-ion plasma with superthermal electrons and positrons. By using the reductive perturbation method, the Korteweg-de Vries equation is derived from the governing equations of ion acoustic waves. An interesting soliton-cnoidal wave solution of the Korteweg-de Vries equation and its quasi-soliton behaviour are presented. The influence of electron superthermality, positron superthermality and positron concentration ratio on characteristics of the quasi-soliton is confirmed to be significant.

Comparison of coupling constant by using momentum spectra and event shape variables in different interactions

2020 ◽  
Vol 98 (10) ◽  
pp. 900-906
Author(s):  
R. Saleh-Moghaddam ◽  
M.E. Zomorrodian
Keyword(s):  
Quantum Chromodynamics ◽  
Strong Coupling ◽  
Event Shape ◽  
Coupling Constant ◽  
Main Text ◽  
Shape Distribution ◽  
Electron Positron ◽  
Momentum Spectra ◽  
Dispersive Model ◽  
Event Shape Distribution

We describe in this paper the quantum chromodynamics prediction to calculate the strong coupling constant by using event shape variables as well as momentum spectra. By fitting the dispersive model and employing our parameters on event shape distribution, we obtain the perturbative value of [Formula: see text] = 0.1305 ± 0.0474 and also the non-perturbative value of α0 = 0.5246 ± 0.0516 GeV for electron–proton interactions. Next, by using momentum spectra for the same interactions, we obtain αs = 0.1572 ± 0.029. Our values in both methods are consistent with those obtained from electron–positron annihilations measured previously. When we find coupling constant for different flavours, we observe that they do not affect our results considerably. This is in accordance with quantum chromodynamics theory. All these features will be explained in the main text.

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