Abstract
A search for the rare decay was performed. With the data collected in 2015, corresponding to protons on target, a single event sensitivity of was achieved and no candidate events were observed. We set an upper limit of for the branching fraction of at the 90% confidence level (C.L.), which improved the previous limit by almost an order of magnitude. An upper limit for was also set as at the 90% C.L., where is an invisible boson with a mass of .
- Received 23 October 2018
- Revised 14 December 2018
DOI:https://doi.org/10.1103/PhysRevLett.122.021802
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.
Published by the American Physical Society