Ultrarelativistic polarized positron jets via collision of electron and ultraintense laser beams

Abstract

Relativistic spin-polarized positron beams are indispensable for future electron-positron colliders to test modern high-energy physics theory with high precision. However, present techniques require very large scale facilities for those experiments. We put forward a novel efficient method for generating ultrarelativistic polarized positron beams employing currently available laser fields. For this purpose the generation of polarized positrons via multiphoton Breit-Wheeler pair production and the associated spin dynamics in single-shot interaction of an ultraintense laser pulse with an ultrarelativistic electron beam is investigated in the quantum radiation-dominated regime. The pair production spin asymmetry in strong fields, significantly exceeding the asymmetry of the radiative polarization, produces locally highly polarized particles, which are split by a specifically tailored small ellipticity of the laser field into two oppositely polarized beams along the minor axis of laser polarization. In spite of radiative de-polarization, a dense positron beam with up to about 90% polarization can be generated in tens of femtoseconds. The method may eventually usher high-energy physics studies into smaller-scale laser laboratories.

Ultrafast polarization of an electron beam in an intense bichromatic laser field

“…With increasing interest in high intensity laser-plasma interactions, it is essential to understand lepton spin effects on the overall plasma dynamics through radiation reaction-because of the spindependence in the photon emission rates-and electronpositron pair generation [13]. There has been notable recent interest in spin polarization of leptons in highintensity laser interactions [14][15][16].It is known that initially unpolarized lepton beams radiatively polarize in storage rings due to asymmetries in the rates for synchrotron emission; the so-called Sokolov-Ternov effect [17][18][19]. As a result, their projected spins end up being predominantly anti-aligned with the magnetic field direction.…”

“…With increasing interest in high intensity laser-plasma interactions, it is essential to understand lepton spin effects on the overall plasma dynamics through radiation reaction-because of the spindependence in the photon emission rates-and electronpositron pair generation [13]. There has been notable recent interest in spin polarization of leptons in highintensity laser interactions [14][15][16].…”

Numerical approach to the semiclassical method of pair production for arbitrary spins and photon polarization

“…This stands in contrast to the conventional Furry picture approach where wave functions in the background field must be found. The scheme presented in this paper could also be useful for polarization and spin effect studies, such as the ones seen in [45][46][47]. The semiclassical approach is an approximation, the limits of which are discussed by the authors themselves and additionally in e.g.…”

Generation of polarized particle beams at relativistic laser intensities

“…An intense linearly polarized two-color laser pulse collides head-on with an unpolarized relativistic electron beam, resulting in the emission of photons in the forward direction, which subsequently decay into polarized e + /e − pairs, with spins parallel and antiparallel, respectively, to the laser's magnetic field direction, and with a small divergence angle in the propagation direction (see Figure 4). Wan et al [43] suggest the use of an ultra-intense elliptically polarized laser pulse that collides headon with an unpolarized electron bunch (similar to Li et al [34] for electrons). Again, the radiated high-energy photons decay into polarized electronpositron pairs due to the asymmetry of spin-dependent pair-production probabilities.…”