All-optical ultrafast spin rotation for relativistic charged particle beams

Abstract

An all-optical method of ultrafast spin rotation is put forward to precisely manipulate the polarization of relativistic charged particle beams of leptons or ions. In particular, laser-driven dense ultrashort beams are manipulated via single-shot interaction with a co-propagating moderate temporally asymmetric (frequency-chirped or subcycle THz) laser pulse. Using semi-classical numerical simulations, we find that in a temporally asymmetrical laser field, the spin rotation of a particle can be determined from the flexibly controllable phase retardation between its spin precession and momentum oscillation. An initial polarization of a proton beam can be rotated to any desired orientation (e.g., from the common transverse to the more useful longitudinal polarization) with extraordinary precision (better than 1%) in tens of femtoseconds using a feasible frequencychirped laser pulse. Moreover, the beam qualities, in terms of energy and angular divergence, can be significantly improved in the rotation process. This method has potential applications in various areas involving ultrafast spin manipulation, like laser-plasma, laser-nuclear and high-energy particle physics.

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

“…Moreover, the TSP electron (positron) beam can be directly produced via nonlinear Compton scattering (nonlinear Breit-Wheeler pair production) in a standingwave [42][43][44], elliptically polarized [45,46], or bichromatic laser pulses [47][48][49][50] due to the quantum radiative spin effects, and the LSP ones can be produced via the helicity transfer from circularly polarized γ photons in linear [51] or nonlinear Breit-Wheeler processes [52,53], which are generally preproduced via Compton scattering [54,55] or bremsstrahlung [56]. Very recently, an all-optical spin rotation method has been proposed to generate arbitrarily spin polarized (ASP) lepton and ion beams [57]. Thus, such a strong laser pulse could be used to drive the direct production of muon pairs through the quantum electrodynamics (QED) processes [29], such as the Bethe-Heitler (BH) and trident muon pair productions via the beam-target interaction: γ + Z → µ − + µ + + Z and e − + Z → µ − + µ + + e − + Z, and the triplet and e − e + annihilation muon pair productions via the beam-beam interaction: e − + γ → µ − + µ + + e − and e − + e + → µ − + µ + [58][59][60][61][62].…”