${{\mathit e}^{-}}$ MEAN LIFE $/$ BRANCHING FRACTION

A test of charge conservation. See the “Note on Testing Charge Conservation and the Pauli Exclusion Principle” following this section in our 1992 edition (Physical Review D45 S1 (1992), p.$~$VI.10).
Most of these experiments are one of three kinds: Attempts to observe (a)$~$the 255.5 keV gamma ray produced in ${{\mathit e}^{-}}$ $\rightarrow$ ${{\mathit \nu}_{{{e}}}}{{\mathit \gamma}}$, (b)$~$the (K)$~$shell x$~$ray produced when an electron decays without additional energy deposit, e.g., ${{\mathit e}^{-}}$ $\rightarrow$ ${{\mathit \nu}_{{{e}}}}{{\overline{\mathit \nu}}_{{{e}}}}{{\mathit \nu}_{{{e}}}}$ (``disappearance” experiments), and (c)$~$nuclear de-excitation gamma rays after the electron disappears from an atomic shell and the nucleus is left in an excited state. The last can include both weak boson and photon mediating processes. We use the best ${{\mathit e}^{-}}$ $\rightarrow$ ${{\mathit \nu}_{{{e}}}}{{\mathit \gamma}}$ limit for the Summary Tables.
Note that we use the mean life rather than the half life, which is often reported.

${{\mathit e}}$ $\rightarrow$ ${{\mathit \nu}_{{{e}}}}{{\mathit \gamma}}$ and astrophysical limits

INSPIRE   JSON  (beta) PDGID:
S003T
VALUE (yr) CL% DOCUMENT ID TECN  COMMENT
$\bf{>6.6 \times 10^{28}}$ 90
AGOSTINI
2015B
 BORX ${{\mathit e}^{-}}$ $\rightarrow$ ${{\mathit \nu}}{{\mathit \gamma}}$
• • We do not use the following data for averages, fits, limits, etc. • •
$>5.4 \times 10^{25}$ 90 1
AGOSTINI
2024A
 HPGE ${{\mathit e}^{-}}$ $\rightarrow$ ${{\mathit \nu}}{{\mathit \gamma}}$, ${}^{76}\mathrm {Ge}$ detector
$>1.22 \times 10^{26}$ 68 2
KLAPDOR-KLEIN..
2007
CNTR ${{\mathit e}^{-}}$ $\rightarrow$ ${{\mathit \nu}}{{\mathit \gamma}}$
$>4.6 \times 10^{26}$ 90
BACK
2002
BORX ${{\mathit e}^{-}}$ $\rightarrow$ ${{\mathit \nu}}{{\mathit \gamma}}$
$>3.4 \times 10^{26}$ 68
BELLI
2000B
 DAMA ${{\mathit e}^{-}}$ $\rightarrow$ ${{\mathit \nu}}{{\mathit \gamma}}$, liquid Xe
$>3.7 \times 10^{25}$ 68
AHARONOV
1995B
 CNTR ${{\mathit e}^{-}}$ $\rightarrow$ ${{\mathit \nu}}{{\mathit \gamma}}$
$>2.35 \times 10^{25}$ 68
BALYSH
1993
CNTR ${{\mathit e}^{-}}$ $\rightarrow$ ${{\mathit \nu}}{{\mathit \gamma}}$, ${}^{76}\mathrm {Ge}$ detector
$>1.5 \times 10^{25}$ 68
AVIGNONE
1986
CNTR ${{\mathit e}^{-}}$ $\rightarrow$ ${{\mathit \nu}}{{\mathit \gamma}}$
$>1 \times 10^{39}$ 3
ORITO
1985
ASTR Astrophysical argument
$>3 \times 10^{23}$ 68
BELLOTTI
1983B
 CNTR ${{\mathit e}^{-}}$ $\rightarrow$ ${{\mathit \nu}}{{\mathit \gamma}}$
1  AGOSTINI 2024A search for coincident photons from the direct ${{\mathit e}}$-decay and from residual X-ray or Auger-${{\mathit e}}$ transitions.
2  The authors of A. Derbin et al, arXiv:0704.2047v1 argue that this limit is overestimated by at least a factor of 5.
3  ORITO 1985 assumes that electromagnetic forces extend out to large enough distances and that the age of our galaxy is $10^{10}$ years.
Conservation Laws:
ELECTRIC CHARGE ($\mathit Q$)
References