Stable Neutral Heavy Lepton MASS LIMITS

Note that LEP results in combination with REUSSER 1991 exclude a fourth stable neutrino with $\mathit m<$ 2400 GeV.

Mass $\mathit m$

INSPIRE   JSON  (beta) PDGID:
S077MNS
VALUE (GeV) CL% DOCUMENT ID TECN  COMMENT
$\bf{>45.0}$ 95
ABREU
1992B
 DLPH Dirac
$\bf{>39.5}$ 95
ABREU
1992B
 DLPH Majorana
$>44.1$ 95
ALEXANDER
1991F
 OPAL Dirac
$>37.2$ 95
ALEXANDER
1991F
 OPAL Majorana
$\text{none 3 - 100}$ 90
SATO
1991
KAM2 Kamiokande II
$>42.8$ 95 1
ADEVA
1990S
 L3 Dirac
$>34.8$ 95 1
ADEVA
1990S
 L3 Majorana
$>42.7$ 95
DECAMP
1990F
 ALEP Dirac
1  ADEVA 1990S limits for the heavy neutrino apply if the mixing with the charged leptons satisfies $\vert \mathit U_{1\mathit j}\vert ^2$ $+$ $\vert \mathit U_{2\mathit j}\vert ^2$ $+$ $\vert \mathit U_{3\mathit j}\vert ^2$ $>$ $6.2 \times 10^{-8}$ at ${\mathit m}_{{{\mathit L}^{0}}}$ = 20 GeV and $>~5.1 \times 10^{-10}$ for ${\mathit m}_{{{\mathit L}^{0}}}$ = 40 GeV.
References