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

TL;DR

This paper explores how polarized electron-positron collisions can produce highly polarized muon pairs with controllable spin orientations, offering a new method for generating polarized muon sources for physics research.

Contribution

It introduces a fully spin-resolved cross section calculation and demonstrates the feasibility of producing arbitrarily polarized muon pairs using polarized $e^-e^+$ collisions.

Findings

Arbitrarily polarized muon pairs can be produced with controllable spin components.

About 40% of muon pairs can have longitudinal polarization.

Approximately 60% of muon pairs can have transverse polarization.

Abstract

Generation of arbitrarily spin polarized muon pairs is investigated via polarized $e^-e^+$ collision. We calculate the fully spin-resolved cross section ${\rm d}\sigma_{e^-e^+\rightarrow \mu^-\mu^+}$ and utilize the Monte Carlo method of binary collision to describe the production and polarization processes of muon pairs. We find that, due to the dependence of mixed helicities on the scattering angle, arbitrarily polarized muon pairs with both of the longitudinal and transverse spin components can be produced. The collision of tightly collimated electron and positron beams with highly longitudinal polarization and nC charge can generate about $40\%$ muon pairs with longitudinal polarization and about $60\%$ muon pairs with transverse polarization. The compact high-flux $e^-e^+\rightarrow\mu^-\mu^+$ muon source could be implemented through the next-generation laser-plasma linear collider, and would be essential to facilitate the investigation of fundamental physics and the measurement technology in broad areas.