Abstract

We present the first search for heavy neutral leptons (HNLs) decaying into νe+e- or νπ0 final states in a liquid-argon time projection chamber using data collected with the MicroBooNE detector. The data were recorded synchronously with the NuMI neutrino beam from Fermilab's main injector corresponding to a total exposure of 7.01×1020 protons on target. We set upper limits at the 90% confidence level on the mixing parameter |Uμ4|2 in the mass ranges 10≤mHNL≤150 MeV for the νe+e- channel and 150≤mHNL≤245 MeV for the νπ0 channel, assuming |Ue4|2=|Uτ4|2=0. These limits represent the most stringent constraints in the mass range 35<mHNL<175 MeV and the first constraints from a direct search for νπ0 decays.

Original languageEnglish
Article number041801
JournalPhysical Review Letters
Volume132
Issue number4
DOIs
StatePublished - 26 Jan 2024

Funding

FundersFunder number
Fermi Research Alliance, LLCDE-AC02-07CH11359
High Energy Physics and Nuclear Physics
NSF AI Institute for Artificial Intelligence and Fundamental Interactions
United Kingdom Research and Innovation
National Science Foundation
U.S. Department of Energy
Office of Science
Science and Technology Facilities Council
Royal Society
Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung

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