# Peak search test INSPIRE search

Limits on B(${{\mathit \pi}}$ (or ${{\mathit K}}$) $\rightarrow$ ${{\mathit \mu}}{{\mathit \nu}_{{x}}}$ ).
VALUE CL% DOCUMENT ID TECN  COMMENT
• • • We do not use the following data for averages, fits, limits, etc. • • •
1
 2002
NOMD ${{\mathit \pi}}$ $\rightarrow$ ${{\mathit \mu}}{{\mathit X}}$ for ${\mathit m}_{{{\mathit X}}}$=33.9 MeV
$<6.0 \times 10^{-10}$ 95 2
 2000
CNTR ${{\mathit \pi}}$ $\rightarrow$ ${{\mathit \mu}}{{\mathit X}}$ for ${\mathit m}_{{{\mathit X}}}=33.9$ MeV
3
 2000
CNTR ${{\mathit \pi}}$ $\rightarrow$ ${{\mathit \mu}}{{\mathit X}}$ for ${\mathit m}_{{{\mathit X}}}=33.9$ MeV
$<0.22$ 90 4
 1998
SILI ${\mathit m}_{{{\mathit \nu}_{{x}}}}$= $0.53$ MeV
$<0.029$ 90 4
 1998
SILI ${\mathit m}_{{{\mathit \nu}_{{x}}}}$= $0.75$ MeV
$<0.016$ 90 4
 1998
SILI ${\mathit m}_{{{\mathit \nu}_{{x}}}}$= $1.0$ MeV
$<4 - 6 \times 10^{-5}$ 5
 1996
CNTR ${\mathit m}_{{{\mathit \nu}_{{x}}}}$ = $30 - 33.91$ MeV
$\sim{}\text{ 1}{\times }\text{ 10^}{-16}$ 6
 1995
KARM ${\mathit m}_{{{\mathit \nu}_{{x}}}}$ = $33.9$ MeV
$<4 \times 10^{-7}$ 95 7
 1995
LEPS ${\mathit m}_{{{\overline{\mathit \nu}}_{{x}}}}$ = $33.9$ MeV
$<7 \times 10^{-8}$ 95 7
 1995
LEPS ${\mathit m}_{{{\mathit \nu}_{{x}}}}$ = $33.9$ MeV
$<2.6 \times 10^{-8}$ 95 7
 1995 B
TOF ${\mathit m}_{{{\mathit \nu}_{{x}}}}$ = $33.9$ MeV
$<0.02$ 90
 1987
${\mathit m}_{{{\mathit \nu}_{{x}}}}$=1 MeV
$<1 \times 10^{-3}$ 90
 1987
${\mathit m}_{{{\mathit \nu}_{{x}}}}$=2 MeV
$<6 \times 10^{-5}$ 90
 1987
3 MeV $<$ ${\mathit m}_{{{\mathit \nu}_{{x}}}}$ $<$ 19.5 MeV
$<0.03$ 90 8
 1984
${\mathit m}_{{{\mathit \nu}_{{x}}}}$=2 MeV
$<1 \times 10^{-3}$ 90 8
 1984
${\mathit m}_{{{\mathit \nu}_{{x}}}}$=4 MeV
$<3 \times 10^{-4}$ 90 8
 1984
${\mathit m}_{{{\mathit \nu}_{{x}}}}$=10 GeV
$<5 \times 10^{-6}$ 90 9
 1982
${\mathit m}_{{{\mathit \nu}_{{x}}}}$=330 MeV
$<1 \times 10^{-4}$ 90 9
 1982
${\mathit m}_{{{\mathit \nu}_{{x}}}}$=70 MeV
$<9 \times 10^{-7}$ 90 9
 1982
${\mathit m}_{{{\mathit \nu}_{{x}}}}$=250 MeV
$<0.1$ 90 8
 1981
${\mathit m}_{{{\mathit \nu}_{{x}}}}$=4 MeV
$<7 \times 10^{-5}$ 90 8
 1981
${\mathit m}_{{{\mathit \nu}_{{x}}}}$=10.5 MeV
$<2 \times 10^{-4}$ 90 8
 1981
${\mathit m}_{{{\mathit \nu}_{{x}}}}$=11.5 MeV
$<2 \times 10^{-5}$ 90 8
 1981
${\mathit m}_{{{\mathit \nu}_{{x}}}}=16-$30 MeV
1  ASTIER 2002 search for anomalous pion decay into a 33.9 MeV neutral particle. No evidence was found and the sensitivity to the branching ratio B( ${{\mathit \pi}}$ $\rightarrow$ ${{\mathit \mu}}{{\mathit X}}$ )$\cdot{}$B( ${{\mathit X}}$ $\rightarrow$ ${{\mathit \nu}}{{\mathit e}^{+}}{{\mathit e}^{-}}$ ) is as low as $3.7 \times 10^{-15}$, depending on the ${{\mathit X}}$ lifetime.
2  DAUM 2000 search for anomalous pion decay into a 33.9$~$MeV neutral particle that might be responsible for the time-distribution anomaly observed by the KARMEN Collaboration.
3  FORMAGGIO 2000 search for anomalous pion decay into a 33.9$~$MeV neutral particle ${{\mathit Q}^{0}}$ that might be responsible for the time-distribution anomaly observed by the KARMEN Collaboration. In the E815 (NuTeV) experiment at Fermilab no evidence was found, with sensitivity for the pion branching ratio B( ${{\mathit \pi}}$ $\rightarrow$ ${{\mathit \mu}}{{\mathit Q}^{0}}$ )$\cdot{}$B( ${{\mathit Q}^{0}}$ $\rightarrow$ visible) as low as $10^{-13}$.
4  ASSAMAGAN 1998 obtain a limit on heavy neutrino admixture from ${{\mathit \pi}^{+}}$ decay essentially at rest, by measuring with good resolution the momentum distribution of the muons. However, the search uses an ad$~$hoc shape correction. The authors report upper limit for $\vert \mathit U_{{{\mathit \mu}}\mathit x}\vert ^2$ of $0.22$ for ${\mathit m}_{{{\mathit \nu}}}$ = $0.53$ MeV, $0.029$ for ${\mathit m}_{{{\mathit \nu}}}$ = $0.75$ MeV, and $0.016$ for ${\mathit m}_{{{\mathit \nu}}}$ = $1.0$ MeV at 90$\%$CL.
5  BRYMAN 1996 search for massive unconventional neutrinos of mass ${\mathit m}_{{{\mathit \nu}_{{x}}}}$ in ${{\mathit \pi}^{+}}$ decay.
6  ARMBRUSTER 1995 study the reactions ${}^{12}\mathrm {C}({{\mathit \nu}_{{e}}},{{\mathit e}^{-}}$) ${}^{12}\mathrm {N}$ and ${}^{12}\mathrm {C}({{\mathit \nu}},{{\mathit \nu}^{\,'}}$) ${}^{12}\mathrm {C}^{*}$ induced by neutrinos from ${{\mathit \pi}^{+}}$ and ${{\mathit \mu}^{+}}$ decay at the ISIS neutron spallation source at the Rutherford-Appleton laboratory. An anomaly in the time distribution can be interpreted as the decay ${{\mathit \pi}^{+}}$ $\rightarrow$ ${{\mathit \mu}^{+}}{{\mathit \nu}_{{x}}}$ , where ${{\mathit \nu}_{{x}}}$ is a neutral weakly interacting particle with mass $\approx{}33.9$ MeV and spin 1/2. The lower limit to the branching ratio is a function of the lifetime of the new massive neutral particle, and reaches a minimum of a few ${\times }10^{-16}$ for ${{\mathit \tau}_{{x}}}\sim{}5~$s.
7  From experiments of ${{\mathit \pi}^{+}}$ and ${{\mathit \pi}^{-}}$ decay in flight at PSI, to check the claim of the KARMEN Collaboration quoted above (ARMBRUSTER 1995 ).
8  ${{\mathit \pi}^{+}}$ $\rightarrow$ ${{\mathit \mu}^{+}}{{\mathit \nu}_{{\mu}}}$ peak search experiment.
9  ${{\mathit K}^{+}}$ $\rightarrow$ ${{\mathit \mu}^{+}}{{\mathit \nu}_{{\mu}}}$ peak search experiment.
References:
 ASTIER 2002
PL B527 23 New Results on a Search for a 33.9-Mev/$\mathit c{}^{2}$ Neutral Particle from ${{\mathit \pi}^{+}}$ Decay in the NOMAD Experiment
 DAUM 2000
PRL 85 1815 The KARMEN Time Anomaly: Search for a Neutral Particle of Mass 33.9 MeV in Pion Decay
 FORMAGGIO 2000
PRL 84 4043 Search for a 33.9 ${\mathrm {MeV}}/\mathit c{}^{2}$ Neutral Particle in Pion Decay
 ASSAMAGAN 1998
PL B434 158 Search for a Heavy Neutrino State in the Decay ${{\mathit \pi}^{+}}$ $\rightarrow$ ${{\mathit \mu}^{+}}{{\mathit \nu}_{{\mu}}}$
 BRYMAN 1996
PR D53 558 Search for Massive Neutrinos in ${{\mathit \pi}^{+}}$ $\rightarrow$ ${{\mathit \mu}^{+}}{{\mathit \nu}}$ Decay
 ARMBRUSTER 1995
PL B348 19 Anomaly in the Time Distribution of Neutrinos from a Pulsed Beam Stop Source
 BILGER 1995
PL B363 41 Search for the Hypothetical ${{\mathit \pi}}$ $\rightarrow$ ${{\mathit \mu}}{{\mathit X}}$ Decay
 DAUM 1995B
PL B361 179 Search for a Neutral Particle of Mass 33.9 MeV in Pion Decay
 DAUM 1987
PR D36 2624 Search for Admixture of Massive Neutrinos in the Decay ${{\mathit \pi}^{+}}$ $\rightarrow$ ${{\mathit \mu}^{+}}{{\mathit \nu}}$
 MINEHART 1984
PRL 52 804 Search for Admixtures of Massive Neutrinos in the Decay ${{\mathit \pi}^{+}}$ $\rightarrow$ ${{\mathit \mu}^{+}}{{\overline{\mathit \nu}}}$
 HAYANO 1982
PRL 49 1305 Heavy Neutrino Search using ${{\mathit K}_{{\mu2}}^{+}}$ Decay
 ABELA 1981
PL 105B 263 Search for an Admixture of Heavy Neutrino in Pion Decay