Searching for new physics at μ → e facilities with μ⁺ and π⁺ decays at rest

Hill, Richard J.; Plestid, Ryan; Zupan, Jure

doi:10.1103/physrevd.109.035025

Published February 1, 2024 | Version Published

Journal Article Open

Searching for new physics at μ → e facilities with μ⁺ and π⁺ decays at rest

We investigate the ability of $μ \to e$ facilities, Mu2e and COMET, to probe, or discover, new physics with their detector validation datasets. The validation of the detector response may be performed using a dedicated run with $μ^{+}$ , collecting data below the Michel edge, ${Eₑ} ≲ 52 MeV$ ; an alternative strategy using $π^{⁺} \to {e⁺} {νₑ}$ may also be considered. We focus primarily on a search for a monoenergetic $e^{+}$ produced via two-body decays $μ^{⁺} \to e^{⁺} X$ or $π^{⁺} \to {e⁺} X$ , with $X$ a light new physics particle. Mu2e can potentially explore new parameter space beyond present astrophysical and laboratory constraints for a set of well motivated models including axionlike particles with flavor violating couplings ( $μ^{+} \to e^{+} a$ ), massive $Z^{'}$ bosons ( ${μ⁺} \to Z^{'} {e⁺}$ ), and heavy neutral leptons ( ${π⁺} \to e^{⁺} N$ ). The projected sensitivities presented herein can be achieved in a matter of days.

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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.

Funding

Funded by SCOAP³.

Acknowledgement

This work began from a series of discussions with Shihua Huang, David Koltick, and Pavel Murat. We acknowledge their contributions at various stages of this work and thank them for helping us understand the challenges that must be overcome at an experiment such as Mu2e. We thank Michael Hedges for his work on the $π \to e ν$ calibration at Mu2e. We thank Diego Redigolo for useful discussions and feedback regarding massless axion searches, Lorenzo Calibbi for suggestions for tau lepton searches for ALPs, and Matheus Hostert for suggestions on HNL induced CLFV couplings. We thank Matheus Hostert and Diego Redigolo for feedback on an early version of this manuscript. We thank Robert Bernstein, Stefano Miscetti, and the broader Mu2e Collaboration for detailed feedback on the final version of this work and coordination with Ref. [61]. We thank Yoshi Kuno for communications regarding COMET, and Robert Schrock for clarifications on HNL mixing limits. This work was supported by the U.S. Department of Energy, Office of Science, Office of High Energy Physics, under Award No. DE-SC0019095. This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics. J. Z. acknowledges support in part by the DOE Grants No. DE-SC0011784 and No. DE-SC1019775, and the NSF Grant No. OAC-2103889. R. P. acknowledges support from the U.S. Department of Energy, Office of Science, Office of High Energy Physics, under Award No. DE-SC0011632 and the Neutrino Theory Network Program Grant under Award No. DE-AC02-07CHI11359, and by the Walter Burke Institute for Theoretical Physics. Part of this research was performed at the Kavli Institute for Theoretical Physics which is supported in part by the National Science Foundation under Grant No. NSF PHY-1748958 and at the Aspen Center for Physics, which is supported by the National Science Foundation Grant No. PHY-1607611. This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of High Energy Physics, under Award No. DE-SC0011632.

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Additional details

ISSN: 2470-0029

United States Department of Energy
DE-SC0019095
United States Department of Energy
DE-AC02-07CH11359
United States Department of Energy
DE-SC0011784
United States Department of Energy
DE-SC1019775
National Science Foundation
OAC-2103889
United States Department of Energy
DE-SC0011632
United States Department of Energy
DE-AC02-07CHI11359
California Institute of Technology
Walter Burke Institute for Theoretical Physics
National Science Foundation
PHY-1748958
National Science Foundation
PHY-1607611
SCOAP3

Caltech groups: Walter Burke Institute for Theoretical Physics

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Searching for new physics at μ → e facilities with μ⁺ and π⁺ decays at rest

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Searching for new physics at μ → e facilities with μ⁺ and π⁺ decays at rest

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Copyright and License

Funding

Acknowledgement

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PhysRevD.109.035025.pdf

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Additional details

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Funding

Caltech Custom Metadata