| $<2 \times 10^{-5}$ |
95 |
1 |
|
ATLS |
| $<1 \times 10^{-9}$ |
90 |
2 |
|
T2K |
| $<1 \times 10^{-4}$ |
90 |
3 |
|
BES3 |
| $<1 \times 10^{-8}$ |
90 |
4 |
|
PIEN |
| $<3 \times 10^{-7}$ |
90 |
5 |
|
NA62 |
| $<3 \times 10^{-5}$ |
95 |
6 |
|
DLPH |
| $<2 \times 10^{-5}$ |
95 |
7 |
|
DLPH |
| $<1 \times 10^{-5}$ |
90 |
8 |
|
|
| $<2 \times 10^{-7}$ |
90 |
8 |
|
|
| $<1 \times 10^{-7}$ |
|
9, 10 |
|
CNTR |
| $<2 \times 10^{-9}$ |
|
11, 10 |
|
CNTR |
| $<1 \times 10^{-7}$ |
90 |
12 |
|
CHRM |
| $<1 \times 10^{-7}$ |
90 |
13 |
|
BEBC |
| • • • We do not use the following data for averages, fits, limits, etc. • • • |
|
|
14 |
|
BELL |
|
1
Limit from prompt lepton number violating trilepton search.
|
|
2
${{\mathit K}^{+}}$ $\rightarrow$ ${{\mathit e}^{+}}{{\mathit \nu}_{{x}}}$ , with ${{\mathit \nu}_{{x}}}$ decay through ${{\mathit U}}_{ {{\mathit e}} {{\mathit x}} }$. ABE 2019B also considers bounds on $\vert {{\mathit U}}_{ {{\mathit \ell}} {{\mathit x}} }{{\mathit U}}_{ {{\mathit \ell}^{\,'}} {{\mathit x}} }\vert $ for combinations of lepton flavors in the ${{\mathit \nu}_{{x}}}$ decay final state.
|
|
3
Searches for a Majorana Heavy Neutral Lepton producing a ${{\mathit \pi}^{-}}{{\mathit e}^{+}}$ resonance in the same sign dilepton decay ${{\mathit D}}$ $\rightarrow$ ${{\mathit K}}{{\mathit \pi}^{-}}{{\mathit e}^{+}}{{\mathit e}^{+}}$ .
|
|
4
Search for ${{\mathit \pi}^{+}}$ $\rightarrow$ ${{\mathit e}^{+}}{{\mathit \nu}_{{x}}}$ .
|
|
5
Search for ${{\mathit K}^{+}}$ $\rightarrow$ ${{\mathit e}^{+}}{{\mathit \nu}_{{x}}}$ .
|
|
6
Search for prompt ${{\mathit \nu}_{{x}}}$ decay signatures.
|
|
7
Search for displaced ${{\mathit \nu}_{{x}}}$ decay signatures.
|
|
8
Searches for ${{\mathit K}}$ or ${{\mathit \pi}}$ $\rightarrow$ ${{\mathit e}^{+}}{{\mathit \nu}_{{x}}}$ , ${{\mathit \nu}_{{x}}}$ $\rightarrow$ ${{\mathit e}^{+}}{{\mathit e}^{-}}{{\mathit \nu}_{{e}}}$ using a beam dump experiment at the 70 GeV Serpukhov proton synchrotron. BARANOV 1993 also considers limits for $\vert {{\mathit U}}_{ {{\mathit e}} {{\mathit x}} }{{\mathit U}}_{ {{\mathit \mu}} {{\mathit x}} }\vert $ from ${{\mathit K}}$ or ${{\mathit \pi}}$ $\rightarrow$ ${{\mathit \mu}^{+}}{{\mathit \nu}_{{x}}}$ , ${{\mathit \nu}_{{x}}}$ $\rightarrow$ ${{\mathit e}^{+}}{{\mathit e}^{-}}{{\mathit \nu}_{{e}}}$ .
|
|
9
${{\mathit \pi}^{+}}$ $\rightarrow$ ${{\mathit e}^{+}}{{\mathit \nu}_{{x}}}$ , with ${{\mathit \nu}_{{x}}}$ decay through ${{\mathit U}}_{ {{\mathit e}} {{\mathit x}} }$.
|
|
10
BERNARDI 1988 also considers bounds on $\vert {{\mathit U}}_{ {{\mathit e}} {{\mathit x}} }{{\mathit U}}_{ {{\mathit \mu}} {{\mathit x}} }\vert $.
|
|
11
${{\mathit K}^{+}}$ $\rightarrow$ ${{\mathit e}^{+}}{{\mathit \nu}_{{x}}}$ , with ${{\mathit \nu}_{{x}}}$ decay through ${{\mathit U}}_{ {{\mathit e}} {{\mathit x}} }$.
|
|
12
${{\mathit D}^{+}}$ $\rightarrow$ ${{\mathit e}^{+}}{{\mathit \nu}_{{x}}}$ , with ${{\mathit \nu}_{{x}}}$ $\rightarrow$ ${{\mathit e}^{-}}{{\mathit \ell}^{+}}{{\mathit \nu}_{{{{\mathit \ell}}}}}$ .
|
|
13
${{\mathit D}^{+}}$ $\rightarrow$ ${{\mathit e}^{+}}{{\mathit \nu}_{{x}}}$ , with ${{\mathit \nu}_{{x}}}$ $\rightarrow$ ${{\mathit e}^{-}}{{\mathit \ell}^{+}}{{\mathit \nu}_{{{{\mathit \ell}}}}}$ or ${{\mathit \nu}_{{x}}}$ $\rightarrow$ ${{\mathit e}^{-}}{{\mathit \pi}^{+}}$ .
|
|
14
PARK 2016 quotes an approximate limit B( ${{\mathit B}^{+}}$ $\rightarrow$ ${{\mathit e}^{+}}{{\mathit \nu}_{{x}}}$ ) $<$ $3 \times 10^{-6}$ in the mass range ${\mathit m}_{{{\mathit \nu}_{{x}}}}$ $\sim{}$ $0.2 - 1.4$ GeV.
|
