Bright γ rays source and nonlinear Breit-Wheeler pairs in the collision of high density particle beams

F Del Gaudio,L O Silva,R A Fonseca,W B Mori,T Grismayer

doi:10.1103/physrevaccelbeams.22.023402

Abstract

The collision of ultrashort high-density $e^-$ or $e^-$ and $e^+$ beams at 10s of GeV, to be available at the FACET II and in laser wakefield accelerator experiments, can produce highly collimated $\gamma$ rays (few GeVs) with peak brilliance of $10^{27}~\mathrm{ph/s~mm^2 mrad^2 0.1\% BW}$ and up to $10^5$ nonlinear Breit-Wheeler pairs. We provide analytical estimates of the photon source properties and of the yield of secondary pairs, finding excellent agreement with full-scale 3D self-consistent particle-in-cell simulations that include quantum electrodynamics effects. Our results show that beam-beam collisions can be exploited as secondary sources of $\gamma$ rays and provide an alternative to beam-laser setups to probe quantum electrodynamics effects at the Schwinger limit.

Highlights

Colliders are a cornerstone of fundamental physics of paramount importance to probe the constituents of matter
In this work we show that disruption, beamstrahlung, and pair production, which were previously regarded as detrimental effects, do have appealing potential from a fundamental physics and from a secondary source perspective
The quantum regime is accessible in electron-positron, or electron-electron, collisions of round beams at considerably lower energy (E ∼ 10s GeV), if the spot size at the collision is small (σ0 ∼ μm) and the beam current (I ∼ 100s kA) is high. Such beams should be available at the new SLAC facility, FACET II [12], and in the generation of Laser Wakefield Accelerators (LWFA) experiments, opening new exciting opportunities

Summary

INTRODUCTION

Colliders are a cornerstone of fundamental physics of paramount importance to probe the constituents of matter. Beam disruption arises when the collective field of these beams focuses (unlike charges e−eþ), deflects, or blows apart (like charges e−e−) each beam [1,2] such that the beam density profile is significantly altered or the number of collisions may be reduced During this process, beamstrahlung photons are emitted via nonlinear Compton scattering, and in turn can decay into electron-positron pairs via the multiphoton Breit-Wheeler mechanism [5,6]. The quantum regime is accessible in electron-positron, or electron-electron, collisions of round beams at considerably lower energy (E ∼ 10s GeV), if the spot size at the collision is small (σ0 ∼ μm) and the beam current (I ∼ 100s kA) is high Such beams should be available at the new SLAC facility, FACET II [12], and in the generation of Laser Wakefield Accelerators (LWFA) experiments, opening new exciting opportunities. This idea was briefly mentioned but overlooked in the context of TeV colliders [10,31]

PHYSICAL PICTURE

ANALYTICAL MODEL

SIMULATIONS

DISCUSSION AND CONCLUSIONS