# 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 $\boldsymbol m$ INSPIRE search

VALUE (GeV) CL% DOCUMENT ID TECN  COMMENT
$\bf{>45.0}$ 95
 1992 B
DLPH Dirac
$\bf{>39.5}$ 95
 1992 B
DLPH Majorana
$>44.1$ 95
 1991 F
OPAL Dirac
$>37.2$ 95
 1991 F
OPAL Majorana
$\text{none 3 - 100}$ 90
 1991
KAM2 Kamiokande II
$>42.8$ 95 1
 1990 S
L3 Dirac
$>34.8$ 95 1
 1990 S
L3 Majorana
$>42.7$ 95
 1990 F
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:
 ABREU 1992B
PL B274 230 Searches for Heavy Neutrinos from ${{\mathit Z}^{0}}$ Decays
 ALEXANDER 1991F
ZPHY C52 175 Measurement of the ${{\mathit Z}^{0}}$ Line Shape Parameters and the Electroweak Couplings of Charged Leptons
 SATO 1991
PR D44 2220 Mass Limits for Dark Matter Particles Derived from High Energy Neutrinos from the Sun
PL B251 321 A Search for Heavy Charged and Neutral Leptons from ${{\mathit Z}^{0}}$ Decays
PL B236 511 A Search for New Quarks and Leptons from ${{\mathit Z}^{0}}$ Decay