Semiclassical pair production rate for rotating electric fields

Abstract

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...

Nonperturbative pair production in interpolating fields

“…Another motivation for this paper is recent interest in pair creation in two-component, rotating fields, which model the electric antinodes of a circularly polarised standing wave [33][34][35][36]. We will here extend these calculations to electric fields depending on our interpolating coordinates, and with up to three components.…”

Boson pair production in arbitrarily polarized electric fields

“…Additionally, it is found that the difference between the number density of created spin-up electrons and spindown electrons becomes larger as the ellipticity increases, and finally the latter one dominates the pair creation process. This is a spin polarization effect [30,32,47], and may be a new way to produce longitudinally polarized relativistic electron (positron) beams which are widely used in high-energy physics. For the convenience of elaboration, we define the degree of spin polarization (DOSP) as κ = n down − n up n down + n up .…”

“…bsxie@bnu.edu.cn ‡ Corresponding author. lyj@aphy.iphy.ac.cn [30][31][32], effective mass signatures, momentum vortices and ponderomotive effects in multiphoton pair production [33][34][35][36], and so on. However, most of them are found in fermion pair production, and it is not sure whether they still exist in boson pair production.…”

Pair creation in the early universe

“…It is usually refered as to WKB but it is more precise 11,12 to called it the semiclassical scattering method. The semiclassical scattering method has been successfully applied in flat spacetime problems for a two-components electrical field 13 as well as in 4D and 3D…”