Second Order QED Processes in an Intense Electromagnetic Field

Abstract

Some non linear, second order QED processes in the presence of intense plane electromagnetic waves are investigated. Analytic expressions with general kinematics are derived for Compton scattering and e + e − pair production in a circularly polarised external electromagnetic field. Special kinematics, including collinear photons and vanishing external field intensity, are employed to show that the general expressions reduce to expressions obtained in previous work. The differential cross sections were investigated numerically for photon energies up to 50 MeV, external field intensity parameter ν 2 to value 2, and all scattering angles. The variation of full cross sections with respect to external field intensity was also established. The presence of the external field led to resonances in the Compton scattering and pair production differential cross sections. These resonances were investigated by calculating the electron self energy in the presence of the external field. Numerical analysis of the external field electron self energy showed agreement with previous work in appropriate limits. However the more general expressions were utilised to calculate resonance widths. At resonance the differential cross sections were enhanced by several orders of magnitude. The resonances occurred for values of external field intensity parameter ν 2 < 1, lowering the limit of ν 2 ∼ 1 at which point non linear effects in first order external field QED processes become important. Generally, full cross sections increased with increasing external field intensity, though peaking sharply for Compton scattering and levelling off for pair production.An application was made to non linear background studies at e + e − linear colliders. The pair production process and electron self energy were studied for the case of a constant crossed electromagnetic field. It was found that previous analytic expressions required the external field to be azimuthally symmetric. New analytic expressions for the more general non azimuthally symmetric case were developed and a numerical parameter range equivalent to that proposed for future linear collider designs was considered. The resonant pair production cross section exceeded the non resonant one by 5 to 6 orders of magnitude. Extra background pair particles are expected at future linear collider bunch collisions, raising previous estimations.The Physics Department at Monash University provided me with many years of employment and the inspiration to pursue a career in physics. Drs Harry S Perlman and Gordon Troup provided much encouragement to pursue work in the field of QED and were coauthors on more than one occasion.Harry's cigar smoke always provided notice of his presence in the department. Thanks also to Dr.Peter Derlet who was a group member worthy of emulation and whose latex outlines I made use of.My thanks to John Dawkins, former Australian Minister for Higher Education in the Australian Labour government. His attacks on the Higher Education sector in 1987 and 1988 introduced me to political a...

Advances in QED with intense background fields

“…We note though that historically there have been a larger number of papers on 2 → 2 processes, e − e − → e − e − and e − γ → e − γ, following the seminal papers [285,286] which showed that these processes have resonances at the pole of the propagator of the intermediate particle, which gives another example where one has to take higher-order-in-α corrections into account. The literature on these processes is reviewed in [287]. For more recent papers on 2 → 2 processes see [288] and references therein.…”

Absorption cross section in an intense plane wave background

“…The presence of the phase derivative Φ (see (17)) in the denominator of ( 19) complicates final state integrations, however, and it would be useful to have a simpler, equivalent expression before proceeding. For pulses with no DC components the regulated expression in (19) is exactly equal to…”

“…(See e.g. [12][13][14][15][16][17][18][19] for other processes.) To our knowledge absorption has not been considered in detail for pulsed laser fields (though for the constant field case see [20], and below).…”

Advances in QED with intense background fields

“…We note though that historically there have been a larger number of papers on 2 → 2 processes, e − e − → e − e − and e − γ → e − γ , following the seminal papers [295,296] which showed that these processes have resonances at the pole of the propagator of the intermediate particle, which gives another example where one has to take higher-order-in-α corrections into account. The literature on these processes is reviewed in [297]. For more recent papers on 2 → 2 processes see [298] and references therein.…”