# Heavy Neutral Lepton MASS LIMITS INSPIRE search

Limits apply only to heavy lepton type given in comment at right of data Listings.

See the Quark and Lepton Compositeness, Searches for'' Listings for limits on radiatively decaying excited neutral leptons, $\mathit i.e.$ ${{\mathit \nu}^{*}}$ $\rightarrow$ ${{\mathit \nu}}{{\mathit \gamma}}$ .

VALUE (GeV) CL% DOCUMENT ID TECN  COMMENT
$\bf{>101.3}$ 95
 2001 B
L3 Dirac coupling to ${{\mathit e}}$
$\bf{>101.5}$ 95
 2001 B
L3 Dirac coupling to ${{\mathit \mu}}$
$\bf{>90.3}$ 95
 2001 B
L3 Dirac coupling to ${{\mathit \tau}}$
$\bf{>89.5}$ 95
 2001 B
L3 Majorana coupling to ${{\mathit e}}$
$\bf{>90.7}$ 95
 2001 B
L3 Majorana coupling to ${{\mathit \mu}}$
$\bf{>80.5}$ 95
 2001 B
L3 Majorana coupling to ${{\mathit \tau}}$
• • • We do not use the following data for averages, fits, limits, etc. • • •
$>76.0$ 95
 2000 I
OPAL Majorana, coupling to ${{\mathit e}}$
$>88.0$ 95
 2000 I
OPAL Dirac, coupling to ${{\mathit e}}$
$>76.0$ 95
 2000 I
OPAL Majorana, coupling to ${{\mathit \mu}}$
$>88.1$ 95
 2000 I
OPAL Dirac, coupling to ${{\mathit \mu}}$
$>53.8$ 95
 2000 I
OPAL Majorana, coupling to ${{\mathit \tau}}$
$>71.1$ 95
 2000 I
OPAL Dirac, coupling to ${{\mathit \tau}}$
$>76.5$ 95
 1999 O
DLPH Dirac coupling to ${{\mathit e}}$
$>79.5$ 95
 1999 O
DLPH Dirac coupling to ${{\mathit \mu}}$
$>60.5$ 95
 1999 O
DLPH Dirac coupling to ${{\mathit \tau}}$
$>63$ 95 1, 2
 1996 S
ALEP Dirac
$>54.3$ 95 1, 3
 1996 S
ALEP Majorana
1  BUSKULIC 1996S requires the decay length of the heavy lepton to be $<1~$cm, limiting the square of the mixing angle $\vert \mathit U_{ {{\mathit \ell}} {{\mathit j}} }\vert ^2$ to $10^{-10}$.
2  BUSKULIC 1996S limit for mixing with ${{\mathit \tau}}$. Mass is $>63.6$ GeV for mixing with ${{\mathit e}}$ or ${{\mathit \mu}}$.
3  BUSKULIC 1996S limit for mixing with ${{\mathit \tau}}$. Mass is $>55.2$ GeV for mixing with ${{\mathit e}}$ or ${{\mathit \mu}}$.
References:
 ACHARD 2001B
PL B517 75 Search for Heavy Neutral and Charged Leptons in ${{\mathit e}^{+}}{{\mathit e}^{-}}$ Annihilation at LEP
 ABBIENDI 2000I
EPJ C14 73 Search for Unstable Heavy and Excited Leptons at LEP-2
 ABREU 1999O
EPJ C8 41 Search for Composite and Exotic Fermions at LEP-2
 BUSKULIC 1996S
PL B384 439 Search for Heavy Lepton Pair Production in ${{\mathit e}^{+}}{{\mathit e}^{-}}$ Collisions at the Centre-of-Mass Energies of 130 and 136 GeV