Status of the DeeMe Experiment, an Experimental Search for $\mu$-$e$ Conversion at J-PARC MLF

TL;DR

The DeeMe experiment aims to detect muon-to-electron conversion with significantly improved sensitivity at J-PARC MLF, involving recent detector development, beamline construction, and preliminary measurements to prepare for future searches.

Contribution

This paper reports on the current status and recent progress of the DeeMe experiment, including detector fabrication, beamline setup, and initial electron spectrum measurements.

Findings

Construction of the secondary beamline is underway.

Four tracking detectors have been manufactured.

Initial measurements of electron momentum spectrum have been performed.

Abstract

The DeeMe experiment is planned to search for muon-to-electron conversion at J-PARC MLF. Our goal is to measure the process with a single event sensitivity of $1 \times 10^{-13}$ or $2 \times 10^{-14}$ for a graphite or silicon carbide target. That is one or two orders of magnitude better than the current upper limits, $7 \times 10^{-13}$ for a gold target by the SINDRUM-II experiment at PSI and $4.6 \times 10^{-12}$ for a titanium target by the experiment at TRIUMF. We are in the middle of preparation for the experiment. The construction of the secondary beamline, H Line, is now in progress. Four tracking detectors have been manufactured in 2017, and the optimization study of the filling gas is ongoing to improve the performance. After getting the better hit efficiency, we measured the momentum spectrum of electrons produced through muon-decay-in-orbit from a carbon target at J-PARC MLF D2 Area in March, 2019. In this paper, the preparation status of the DeeMe experiment will be presented.