Does muon-to-electron conversion occur at rates near 10^-16? · revision history

Revision 2

Accepted · core change · record

Changes against revision 1:

Title · changed
Revision 1: Does muon-to-electron conversion occur at rates near 1e-16?
Revision 2: Does muon-to-electron conversion occur at rates near $10^{-16}$?
Plain
The SM forbids a muon from turning into an electron without neutrinos, except at hopelessly tiny rates. Seeing it would prove new physics acting on flavor.
Precise · changed · core
Revision 1: Measure or bound the coherent conversion rate $R_{\mathrm{mue}} = \Gamma(\mu- N \to e- N)/\Gamma(\mu- \mathrm{capture})$ on aluminum at single-event sensitivity $\sim 1e-17$ (Mu2e, COMET), versus the SINDRUM II gold limit of about $7e-13$. Combine with $\mu \to e\gamma$ (MEG II) and $\mu \to 3e$ (Mu3e) to identify the operator responsible if seen.
Revision 2: Measure or bound the coherent conversion rate $R_{\mathrm{mue}} = \Gamma(\mu- N \to e- N)/\Gamma(\mu- \mathrm{capture})$ on aluminum at single-event sensitivity $\sim 10^{-17}$ (Mu2e, COMET), versus the SINDRUM II gold limit of about $7 \times 10^{-13}$. Combine with $\mu \to e\gamma$ (MEG II) and $\mu \to 3e$ (Mu3e) to identify the operator responsible if seen.
Settled by · changed · core
Revision 1: Mu2e at Fermilab and COMET at J-PARC reaching single-event sensitivity near 1e-17.
Revision 2: Mu2e at Fermilab and COMET at J-PARC reaching single-event sensitivity near $10^{-17}$.
Kind
well-posed
Answer type
yes-no
References
(empty)
Literature status
open
Status note · changed
Revision 1: MEG II reported $\mathrm{BR}(\mu \to e \gamma) < \sim 1.5e-13$ in 2025 (moderate confidence on the exact value); Mu2e and COMET are expected to start physics running around 2027.
Revision 2: MEG II reported $\mathrm{BR}(\mu \to e \gamma) < \sim 1.5 \times 10^{-13}$ in 2025 (moderate confidence on the exact value); Mu2e and COMET are expected to start physics running around 2027.
Posed since
(empty)

Decisions