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Published July 2018 | Submitted + Published
Journal Article Open

Coherent μ-e Conversion at Next-to-Leading Order


We analyze next-to-leading-order (NLO) corrections and uncertainties for coherent μ−e conversion. The analysis is general, but numerical results focus on ^(27)Al, which will be used in the Muon-to-electron conversion (Mu2e) experiment. We obtain a simple expression for the branching ratio in terms of Wilson coefficients associated with possible physics beyond the standard model and a set of model-independent parameters determined solely by standard model dynamics. For scalar-mediated conversion, we find that NLO two-nucleon contributions can significantly decrease the branching ratio, potentially reducing the rate by as much as 50%. The pion-nucleon σ term and quark masses give the dominant sources of parametric uncertainty in this case. For vector-mediated conversion, the impact of NLO contributions is considerably less severe, while the present theoretical uncertainties are comparable to parametric uncertainties.

Additional Information

© 2018 The Author(s). 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. Received 23 January 2018; published 27 July 2018. We thank Mark B. Wise for many helpful discussions throughout the course of this work and Jordy de Vries, Martin Hoferichter, and Jose Manuel Alarcon Soriano for helpful comments on the draft. This work was supported in part under U.S. Department of Energy contracts DE-SC0011632 (A.B.) and DE-SC0011095 (M.J.R.M.).

Attached Files

Published - PhysRevC.98.015208.pdf

Submitted - 1710.02129.pdf


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