$\gamma\gamma$ Beam-beam Parameter Study for a 3 TeV PWFA Linear Collider

TL;DR

This study uses simulations to analyze beam-beam interactions in a 3 TeV PWFA gamma-gamma collider, finding that luminosity is unaffected by electron beam length within a certain range and can be maximized by optimizing beta functions.

Contribution

It demonstrates that at 3 TeV, the luminosity and spectrum sharpness are independent of electron beam length, and proposes parameter sets that outperform CLIC-based colliders in luminosity.

Findings

Luminosity is independent of electron beam length between 2-10 μm.

Maximizing beta functions enhances total luminosity.

Proposed parameters yield higher luminosity but increased background particles.

Abstract

Our beam-beam parameter study using beam-beam simulations and PWFA (particle-driven plasma acceleration) beam parameters indicates that at 3 TeV, for examined electron beam lengths ${2~\mu\mathrm{m}\leq\sigma_z\leq 10~\mu\mathrm{m}}$, the total luminosity, as well as the sharpness of the luminosity spectrum for a $\gamma\gamma$ collider are independent of the beam length of the electron beams used to scatter the photons, given that the hourglass effect is avoided. The total luminosity can consequently be maximised by minimising the horizontal and vertical beta functions $\beta_{x,y}^*$ at the interaction point. Furthermore, we performed background studies in GUINEA-PIG where we considered the smallest currently achievable $\beta_{x,y}^*$ combined with PWFA beam parameters. Simulations results show that our proposed parameter set for a 3 TeV PWFA $\gamma\gamma$ collider is able to deliver a total luminosity significantly higher than a $\gamma\gamma$ collider based on CLIC parameters, but gives rise to more background particles.