Electron-positron pair production in the collision of real photon beams with wide energy distributions

Abstract

The creation of an electron–positron pair in the collision of two real photons, namely the linear Breit–Wheeler process, has never been detected directly in the laboratory since its prediction in 1934 despite its fundamental importance in quantum electrodynamics and high energy astrophysics. In the last few years, several experimental setup have been proposed to observe this process in the laboratory, relying either on thermal radiation, Bremsstrahlung, linear or multiphoton inverse Compton scattering photons sources created by lasers or by the mean of a lepton collider coupled with lasers. In these propositions, the influence of the photons’ energy distribution on the total number of produced pairs has been taken into account with an analytical model only for two of these cases. We hereafter develop a general and original, semi-analytical model to estimate the influence of the photons energy distribution on the total number of pairs produced by the collision of two such photon beams, and give optimum energy parameters for some of the proposed experimental configurations. Our results shows that the production of optimum Bremsstrahlung and linear inverse Compton sources are, only from energy distribution considerations, already reachable in today’s facilities. Despite its less interesting energy distribution features for the linear Breit–Wheeler pair production, the photon sources generated via multiphoton inverse Compton scattering by the propagation of a laser in a micro-channel can also be interesting, thank to the high collision luminosity that could eventually be reached by such configurations. These results then gives important insights for the design of experiments intended to detect linear Breit–Wheeler produced positrons in the laboratory for the first time.

Generation of arbitrarily polarized muon pairs via polarized $e^-e^+$ collision

“…In the simulations, we consider that the energy distribution in the given electron and positron beams is spatially homogeneous and defined by a characteristic constant, then the muon yield N sc in a single e − e + collision can be written as [70]…”

Report on progress in physics: observation of the Breit–Wheeler process and vacuum birefringence in heavy-ion collisions

“…In the last ten years, there have been theory proposals on how to discover the BW process in photon-photon collisions using high-intensity lasers [87] and a vacuum hohlraum [88], which explicitly stated that the BW process 'has never been observed in the laboratory'. However, creative experimental designs and increasing laser power may render the exclusive BW process achievable at laser facilities [86,87,[89][90][91] in the near future. Clearly, the community considers laser photons as a valid source of photons for achieving the BW process.…”

“…It is often considered that the transverse momentum of the photons in HICs is related to the transverse dimensions of the nuclei and the photon virtuality, according to the uncertainty principle [114]. This has been used as an argument [89,102,115,116] that the e + e − pair production from HICs is not the BW process, despite the original proposal from Breit and Wheeler in their seminal paper [9]. In this section, we follow [117] via the S-Matrix derivation to illustrate the approximation which results in the EPA and propose a well-defined criterion for the BW process in relativistic HICs to clearly separate it from the Landau-Lifshitz [16] and Bethe-Heitler [14] processes involving virtual photons (see figure 8).…”