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Limits on $\vert \mathit U_{{{\mathit e}}\mathit x}\vert ^2$ as Function of ${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$

Searches for Decays of Massive ${{\mathit \nu}}$

INSPIRE JSON (beta) PDGID:

Limits on $\vert \mathit U_{{{\mathit e}}\mathit x}\vert ^2$ as function of ${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$

VALUE

CL%

DOCUMENT ID

TECN

COMMENT

• • We do not use the following data for averages, fits, limits, etc. • •

$<1.6 \times 10^{-4}$

90

CNTR

${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$ = 4 MeV

$<4.5 \times 10^{-5}$

90

CNTR

${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$ = 7 MeV

$<3.8 \times 10^{-5}$

90

CNTR

${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$ = 10 MeV

$<1.5 \times 10^{-3}$

95

L3

${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$=80 GeV

$<0.02$

95

L3

${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$=175 GeV

$<0.3$

95

L3

${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$=200 GeV

$<4 \times 10^{-3}$

95

L3

${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$=80 GeV

$<0.05$

95

L3

${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$= 175 GeV

$<2 \times 10^{-5}$

95

DLPH

${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$=6 GeV

$<3 \times 10^{-5}$

95

DLPH

${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$=50 GeV

$<1.8 \times 10^{-3}$

90

MWPC

${\mathit m}_{{{\mathit \nu}_{{{h}}}}}$ = $1.5$ MeV

$<2.5 \times 10^{-4}$

90

MWPC

${\mathit m}_{{{\mathit \nu}_{{{h}}}}}$ = 4 MeV

$<4.2 \times 10^{-3}$

90

MWPC

${\mathit m}_{{{\mathit \nu}_{{{h}}}}}$ = 9 MeV

$<1 \times 10^{-5}$

90

${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$=100 MeV

$<1 \times 10^{-6}$

90

${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$= 200 MeV

$<3 \times 10^{-7}$

90

${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$= 300 MeV

$<2 \times 10^{-7}$

90

${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$=400 MeV

$<6.2 \times 10^{-8}$

95

L3

${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$=20 GeV

$<5.1 \times 10^{-10}$

95

L3

${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$=40 GeV

$\text{all values ruled out}$

95

MRK2

${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$ $<$ $19.6$ GeV

$<1 \times 10^{-10}$

95

MRK2

${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$= $22$ GeV

$<1 \times 10^{-11}$

95

MRK2

${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$= $41$ GeV

$\text{all values ruled out}$

95

ALEP

${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$= $25.0-42.7$ GeV

$<1 \times 10^{-13}$

95

ALEP

${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$= $42.7-45.7$ GeV

$<5 \times 10^{-3}$

90

HRS

${\mathit m}_{{{\mathit \nu}_{{{x}}}}}=1.8$ GeV

$<2 \times 10^{-5}$

90

HRS

${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$=4 GeV

$<3 \times 10^{-6}$

90

HRS

${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$=6 GeV

$<1.2 \times 10^{-7}$

90

CNTR

${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$=100 MeV

$<1 \times 10^{-8}$

90

CNTR

${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$=200 MeV

$<2.4 \times 10^{-9}$

90

CNTR

${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$=300 MeV

$<2.1 \times 10^{-9}$

90

CNTR

${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$=400 MeV

$<0.02$

68

${\mathit m}_{{{\mathit \nu}_{{{x}}}}}=1.5$ MeV

$<8 \times 10^{-4}$

68

${\mathit m}_{{{\mathit \nu}_{{{x}}}}}=4.0$ MeV

$<8 \times 10^{-3}$

90

CNTR

${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$=400 MeV

$<8 \times 10^{-5}$

90

CNTR

${\mathit m}_{{{\mathit \nu}_{{{x}}}}}=1.7$ GeV

$<8 \times 10^{-8}$

90

CNTR

${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$=100 MeV

$<4 \times 10^{-8}$

90

CNTR

${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$=200 MeV

$<6 \times 10^{-9}$

90

CNTR

${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$=400 MeV

$<3 \times 10^{-5}$

90

CNTR

${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$=150 MeV

$<1 \times 10^{-6}$

90

CNTR

${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$=500 MeV

$<1 \times 10^{-7}$

90

CNTR

${\mathit m}_{{{\mathit \nu}_{{{x}}}}}=1.6$ GeV

$<7 \times 10^{-7}$

90

HLBC

${\mathit m}_{{{\mathit \nu}_{{{x}}}}}=0.4$ GeV

$<8 \times 10^{-8}$

90

HLBC

${\mathit m}_{{{\mathit \nu}_{{{x}}}}}=1.5$ GeV

$<0.01$

90

CNTR

${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$=10 MeV

$<1 \times 10^{-5}$

90

CNTR

${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$=110 MeV

$<6 \times 10^{-7}$

90

CNTR

${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$=410 MeV

$<1 \times 10^{-5}$

90

${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$=160 MeV

$<1 \times 10^{-6}$

90

${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$=480 MeV

¹

BACK 2003A searched for heavy neutrinos emitted from ${}^{8}\mathrm {B}$ decay in the Sun using the decay ${{\mathit \nu}_{{{h}}}}$ $\rightarrow$ ${{\mathit \nu}_{{{e}}}}{{\mathit e}^{+}}{{\mathit e}^{-}}$ in the Counting Test Facility (the prototype of the Borexino detector) and obtained limits on heavy neutrino admixture for the ${{\mathit \nu}_{{{h}}}}$ mass range $1.1 - 12$ MeV.

²	ABREU 1997I long-lived ${{\mathit \nu}_{{{x}}}}$ analysis. Short-lived analysis extends limit to lower masses with decreasing sensitivity except at $3.5$ GeV, where the limit is the same as at 6 GeV.

³	HAGNER 1995 obtain limits on heavy neutrino admixture from the decay ${{\mathit \nu}_{{{h}}}}$ $\rightarrow$ ${{\mathit \nu}_{{{e}}}}{{\mathit e}^{+}}{{\mathit e}^{-}}$ at a nuclear reactor for the ${{\mathit \nu}_{{{h}}}}$ mass range $2 - 9$ MeV.

⁴	BARANOV 1993 is a search for neutrino decays into ${{\mathit e}^{+}}{{\mathit e}^{-}}{{\mathit \nu}_{{{e}}}}$ using a beam dump experiment at the 70 GeV Serpukhov proton synchrotron. The limits are not as good as those achieved earlier by BERGSMA 1983 and BERNARDI 1986, BERNARDI 1988.

⁵	BURCHAT 1990 includes the analyses reported in JUNG 1990, ABRAMS 1989C, and WENDT 1987.

⁶	OBERAUER 1987 bounds from search for ${{\mathit \nu}}$ $\rightarrow$ ${{\mathit \nu}^{\,'}}{{\mathit e}}{{\mathit e}}$ decay mode using reactor (anti)neutrinos.

⁷

COOPER-SARKAR 1985 also give limits based on model-dependent assumptions for ${{\mathit \nu}_{{{\tau}}}}$ flux. We do not list these. Note that for this bound to be nontrivial, $\mathit x$ is not equal to 3, i.e. ${{\mathit \nu}_{{{x}}}}$ cannot be the dominant mass eigenstate in ${{\mathit \nu}_{{{\tau}}}}$ since ${\mathit m}_{{{\mathit \nu}_{{{3}}}}}$ $<$70 MeV (ALBRECHT 1985I). Also, of course, $\mathit x$ is not equal to 1 or 2, so a fourth generation would be required for this bound to be nontrivial.

⁸

BERGSMA 1983B also quote limits on $\vert \mathit U_{{{\mathit e}}3}\vert {}^{2}$ where the index 3 refers to the mass eigenstate dominantly coupled to the ${{\mathit \tau}}$. Those limits were based on assumptions about the ${{\mathit D}_{{{s}}}}$ mass and ${{\mathit D}_{{{s}}}}$ $\rightarrow$ ${{\mathit \tau}}{{\mathit \nu}_{{{\tau}}}}$ branching ratio which are no longer valid. See COOPER-SARKAR 1985.

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