Quantitative Evaluation of a Hybrid Target for Ultraslow-Muon Production in $μ$TRISTAN

Abstract

We present the first quantitative evaluation of the hybrid target concept proposed in $μ$TRISTAN. The $μ$TRISTAN project is a positive-muon collider concept based on the ultraslow-muon production technique, in which thermal muonium emitted from a material surface is subsequently laser-ionized. The hybrid target consists of a pion production target and a surrounding pion- and muon-stopping target that also serves as a muonium-production target. In this paper, Monte Carlo simulations of the hybrid target are performed to evaluate the yield of positive muons stopped near the tungsten surface, where they can contribute to muonium emission. The ultraslow-muon yield at the hybrid target before extraction is estimated to reach the 10$^{-3}$ level per p--Li nuclear collision, assuming unit muon-to-muonium conversion efficiency. This study provides a quantitative benchmark for hybrid-target design toward an intense ultraslow-muon source.