Search for millicharged particles using the MicroBooNE detector

Abstract

We search for millicharged particles using a single-electron scatter signature in the MicroBooNE detector. Using 1.07e21 protons-on-target of data from the Neutrinos at the Main Injector (NuMI) beam, we observe no significant excess compared to the expected backgrounds. We set limits on the production of millicharged particles from the decay of light neutral mesons, covering a mass range of 15 to 400 MeV, and electric charges between 5.17e-4 and 1.88e-2 times the elementary charge. These results improve upon previous constraints from the ArgoNeuT liquid argon-time projection chamber (LArTPC), though they do not represent the most stringent limits to date. This is the first search for millicharged particles using a single-scatter signature in a LArTPC. The analysis targets electron recoils with energies as low as 20 MeV, where the Wire-Cell reconstruction framework yields only a 1 % selection efficiency in its default configuration. We also present the expected sensitivity for a complementary search using a multiple blip scatter signature, aligned with the NuMI beam target, with energies as low as 0.5 MeV, similar to the search performed by ArgoNeuT. This blip-based channel shows lower sensitivity than the single-scatter search for electric charge ranges between 3.75×10−3 and 1.13e-2. Only at the highest mass point of 400 MeV does the blip-based search surpass the sensitivity of the Wire-Cell based single-scatter channel.

Date of Award	19 Mar 2025
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Stefan Söldner-Rembold (Co Supervisor) & Justin Evans (Main Supervisor)