Electrons from Muon Decay in Bound State

TL;DR

This paper analyzes the background contribution of electrons from muon decay in orbit to muon-electron conversion experiments, considering realistic detector resolutions and geometrical effects.

Contribution

It provides a detailed assessment of DIO electrons' impact on signal detection, including the effects of non-Gaussian resolution tails and calorimeter acceptance.

Findings

Non-Gaussian tails do not significantly increase DIO background.

Geometrical acceptance suppresses intermediate electrons from DIO.

Realistic resolution functions are crucial for accurate background estimation.

Abstract

We present results of a study of the muon decay in orbit (DIO) contribution to the signal region of muon - electron conversion. Electrons from DIO are the dominant source of background for muon - electron conversion experiments because the endpoint of DIO electrons is the same as the energy of electrons from elastic muon - electron conversion. The probability of DIO contribution to the signal region was considered for a tracker with Gaussian resolution function and with a realistic resolution function obtained in the application of pattern recognition and momentum reconstruction Kalman filter based procedure to GEANT simulated DIO events. It is found that the existence of non Gaussian tails in the realistic resolution function does not lead to a significant increase in DIO contribution to the signal region. The probability of DIO contribution to the calorimeter signal was studied in dependence on the resolution, assuming a Gaussian resolution function of calorimeter. In this study the geometrical acceptance played an important role, suppressing DIO contribution of the intermediate range electrons from muon decay in orbit.