Sensitivity study of the charged lepton flavor violating process $\tau \to \gamma \mu$ at STCF

TL;DR

This study estimates the sensitivity of the Super τ-Charm Facility to detect the charged lepton flavor violating decay τ → γμ, projecting significant improvements over current limits with increased luminosity and ideal detector performance.

Contribution

It provides a detailed sensitivity analysis for τ → γμ decay detection at STCF, including effects of detector performance and luminosity scaling.

Findings

Sensitivity could reach 8.8×10⁻⁹ with 10 ab⁻¹ luminosity.

Ideal detector performance improves sensitivity to 2.8×10⁻⁸ at 90% CL.

Sensitivity scales with the square root of luminosity.

Abstract

A sensitivity study for the search for the charged lepton flavor violating process $\tau \to \gamma\mu$ at the Super $\tau$-Charm Facility is performed with a fast simulation. With the expected performance of the current detector design and an integrated luminosity of \SI{1}{ab^{-1}} corresponding to one-year of data taking, the sensitivity on the branching fraction (BF) of $\tau \to \gamma\mu$ is estimated to be at the level of \num{e-8}. The sensitivity under different detector performances are also studied. With ideal performance, the BF could be probed to be \num{2.8e-8} at \SI{90}{\percent} confidence level. The sensitivity is expected to scale with the square root of the luminosity, therefore with a total luminosity of \SI{10}{ab^{-1}} corresponding to ten-year of data taking, the sensitivity could reach \num{8.8e-9}, which is about one order of magnitude improvement upon the current best upper limit.