Pair production: The view from the lightfront

Hebenstreit, Florian; Ilderton, Anton; Marklund, Mattias

doi:10.1103/physrevd.84.125022

Cited by 29 publications

(28 citation statements)

References 49 publications

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“…Therefore, previous considerations are often restricted to the analysis of the three-dimensional differential cross sections, see for example [12] for finite beam size effects in e + e − pair production (cf. also [21] and references therein).The aim of the present Letter is to elaborate a method for the calculation of the total cross section in the subthreshold (multi-photon) region accounting for the effect of finite laser pulse duration in e + e − pair production off a probe photon. We denote such a process with a finite pulse and plane wave fronts as finite pulse approximation (FPA).…”

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Enhanced Subthresholde+e−Production in Short Laser Pulses

et al. 2012

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The emission of e + e − pairs off a probe photon propagating through a polarized short-pulsed electromagnetic (e.g. laser) wave field is analyzed. A significant increase of the total cross section of pair production in the subthreshold region is found for decreasing laser pulse duration even in case of moderate laser pulse intensities.PACS numbers: 12.20.Ds, 14.70.Bh The history of the study of e + e − production in γ ′ γ interaction starts with the pioneering work by Breit and Wheeler [1] published in 1934. About thirty years later, Reiss [2] and Narozhnyi, Nikishov and Ritus [3,4] have analyzed the e + e − emission off a photon γ ′ propagating in the field of an intensive polarized monochromatic electromagnetic (e.m.) plane. The e + e − production probabilities were found using the non-perturbative Volkov solutions for the electron and positron wave functions [5].If one identifies the external e.m. field with a laser pulse then most of the early work considers long lasting pulses where the temporal shape can be neglected. We denote this approach as the infinite pulse approximation (IPA). In IPA, electrons e − and positrons e + become quasi-particles with effective quasi-momenta and effective (dressed) masses. Differential and total probabilities of the e + e − pair emission depend on the reduced strength of the e.m. field, where M e is the electron mass (we use c = = 1, e 2 /4π = α = 1/137). Furthermore, the dimensionless variable ζ = s thr s is introduced, where s is the square of the total energy in the center of mass system (c.m.s.) of the Breit-Wheeler process γ ′ + γ → e + + e − and s thr = 4M 2 e is its threshold value. The Ritus variable is then defined by κ = 2ξ/ζ [4]. The case of ζ > 1 corresponds essentially to multi-photon processes. Within IPA, the minimum number of photons γ in the reaction γ ′ +nγ → e + +e − is defined as n min = I(ζ)+1, where I(ζ) is the integer part of ζ. First evidence of the multi-photon Breit-Wheeler process with ζ = 3.83 and 0.1 < ξ < 0.35 was detected at SLAC in the E-144 experiment [6], where the application of IPA is justified since the used laser pulses contain around 10 3 cycles in a shot.The rapidly evolving laser technology [7] can provide the laser power up to 10 24 -10 25 W/cm 2 in near future which is sufficient for the formation of positrons from cascade processes in the photon-electron-positron plasma [8-10] generated by photon-laser [11][12][13], electron-laser [14,15] or laser-laser interactions [16,17] (see [18] for surveys). The next generation of optical laser beams are expected to be essentially short (femtosecond duration) with only a few oscillation of the e.m. field in the pulse to be expected at ELI [19] and CLF [20] facilities. This requires the generalization of the IPA multi-photon process γ ′ + nγ → e + + e − to a finite pulse duration. Formally, this generalization may be done in a straightforward manner by substituting the expansion in Fourier series into Fourier integrals with taking into account the Volkov solution for the finite wave fie...

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Enhanced Subthresholde+e−Production in Short Laser Pulses

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“…Unfortunately, the dependence of this non-perturbative phenomenon on the field profile E(t, r) away from the constant field approximation is still mostly terra incognita. There are many results for fields which depend on one coordinate only, such as space x or time t (see, e.g., [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]), one of the light-cone coordinates x ± = t ± x (see, e.g., [21][22][23][24][25][26][27][28]), or other linear combinations of x and t [29]. In these cases, the underlying (Dirac or Klein-Fock-Gordon) equation simplifies to an ordinary differential equation (allowing for a WKB approach, for example, see also [30][31][32][33][34]).…”

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Dynamically assisted Sauter-Schwinger effect in inhomogeneous electric fields

Schneider

Schützhold

2016

J. High Energ. Phys.

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Via the world-line instanton method, we study electron-positron pair creation by a strong (but sub-critical) electric field of the profile E/ cosh 2 (kx) superimposed by a weaker pulse E / cosh 2 (ωt). If the temporal Keldysh parameter γ ω = mω/(qE) exceeds a threshold value γ crit ω which depends on the spatial Keldysh parameter γ k = mk/(qE), we find a drastic enhancement of the pair creation probability -reporting on what we believe to be the first analytic non-perturbative result for the interplay between temporal and spatial field dependences E(t, x) in the Sauter-Schwinger effect. Finally, we speculate whether an analogous effect (drastic enhancement of tunneling probability) could occur in other scenarios such as stimulated nuclear decay, for example.

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“…the WKB-approximation [17][18][19][20][21][22][23][24][25][26] or the world-line instanton method [27][28][29]. In addition to that there are exact solutions for fields depending on lightcone variables [30,31]. While one-component fields can be used to describe linearly polarized laser fields, one needs two-component fields to study pair creation of circularly polarized fields.…”

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Semiclassical pair production rate for rotating electric fields

Strobel

Xue

2015

Phys. Rev. D

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We semiclassically investigate Schwinger pair production for pulsed rotating electric fields depending on time. To do so we solve the Dirac equation for two-component fields in a WKB-like approximation. The result shows that for two-component fields the spin distribution of produced pairs is generally not 1 : 1. As a result the pair creation rates of spinor and scalar quantum electro dynamics (QED) are different even for one pair of turning points. For rotating electric fields the pair creation rate is dominated by particles with a specific spin depending on the sense of rotation for a certain range of pulse lengths and frequencies. We present an analytical solution for the momentum spectrum of the constant rotating field. We find interference effects not only in the momentum spectrum but also in the total particle number of rotating electric fields.PACS numbers: 12.20. Ds, 11.15.Kc, 11.15.Tk IntroductionSince the first investigations of electron-positron pair creation in strong electric fields, also known as the Schwinger effect, there has been a lot of theoretical investigations of it. However it has not yet been possible to measure it directly due to the exponentially damped pair creation rate ∼ exp(−π/ ) where = E/E c is the field strength E normalized by the critical electric field [1-3]As laser powers in future may get closer to reaching this critical field strength, investigations of the effect are of interest. However there is the possibility that different strong field processes, such as QED cascades, will set in which might prevent reaching critical intensities [4][5][6][7][8][9][10][11][12][13][14].As pointed out in [15] it might be crucial for the detection of the Schwinger effect to evaluate if one can distinguish a QED cascade triggered by an electron which was produced in the Schwinger process from one which was triggered by vacuum impurities. To do so one first has to evaluate the properties of the pairs produced via the Schwinger effect. The simplest field configurations taken into account for cascade calculations are uniformly rotating electrical fields. These are approximative models for the electric fields in the anti-nodes of circularly polarized standing waves. The momentum spectrum of produced electron-positron pairs for rotating fields has been recently investigated numerically for pulsed fields with the help of the real-time Dirac-Heisenberg-Wigner (DHW) formalism [15] as well as analytically for constant rotating fields with help of the semiclassical WKB approximation for spinor QED [16]. Numerical methods usually need a lot of computation time. Semiclassical methods can help to give a better understanding of special features of the momentum spectrum, e.g. interference effects. For one-component fields depending solely on time there exist a lot of semiclassical investigations using e.g. the WKB-approximation [17][18][19][20][21][22][23][24][25][26] or the world-line instanton method [27][28][29]. In addition to that there are exact solutions for fields depending on lightcone variabl...

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Pair production: The view from the lightfront

Cited by 29 publications

References 49 publications

Enhanced Subthresholde+e−Production in Short Laser Pulses

Enhanced Subthresholde+e−Production in Short Laser Pulses

Dynamically assisted Sauter-Schwinger effect in inhomogeneous electric fields

Semiclassical pair production rate for rotating electric fields

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