High-sensitivity follow-up experiments show that indications for a neutrino with mass 17 keV (Simpson, Hime, and others) were not valid. Accordingly, we no longer list the experiments by these authors and some others which made positive claims of 17 keV neutrino emission. Complete listings are given in the 1994 edition (Physical Review D50 1173 (1994)) and in the 1998 edition (The European Physical Journal C3 1 (1998)). We list below only the best limits on $\vert {{\mathit U}_{{{{ex}}}}}\vert ^2$ for each ${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$. See WIETFELDT 1996 for a comprehensive review.

VALUE ($ 10^{-3} $) CL$\%$ ${\mathrm {{\mathit m}_{{{\mathit \nu}_{{{j}}}}} (keV)}}$ ISOTOPE METHOD DOCUMENT ID • • We do not use the following data for averages, fits, limits, etc. • • $ \text{<4 - 20} $ $90$ $700 - 3500$ ${}^{38m}$K Trap 1 TRINCZEK 2003 $ \text{<9 - 116} $ $95$ $1 - 0.1$ ${}^{187}\mathrm {Re}$ cryog. 2 GALEAZZI 2001 $ <1 $ $95$ $10 - 90$ ${}^{35}\mathrm {S}$ Mag spect 3 HOLZSCHUH 2000 $ <4 $ $95$ $14 - 17$ ${}^{241}\mathrm {Pu}$ Electrostatic spec 4 DRAGOUN 1999 $ <1 $ $95$ $4 - 30$ ${}^{63}\mathrm {Ni}$ Mag spect 5 HOLZSCHUH 1999 $ \text{<10 - 40} $ $90$ $370 - 640$ ${}^{37}\mathrm {Ar}$ EC ion recoil 6 HINDI 1998 $ \text{<10} $ $95$ $1$ ${}^{3}\mathrm {H}$ SPEC 7 HIDDEMANN 1995 $ \text{<6} $ $95$ $2$ ${}^{3}\mathrm {H}$ SPEC 7 HIDDEMANN 1995 $ \text{<2} $ $95$ $3$ ${}^{3}\mathrm {H}$ SPEC 7 HIDDEMANN 1995 $ <0.7 $ $99$ $16.3 - 16.6$ ${}^{3}\mathrm {H}$ Prop chamber 8 KALBFLEISCH 1993 $ <2 $ $95$ $13 - 40$ ${}^{35}\mathrm {S}$ Si(Li) 9 MORTARA 1993 $ <0.73 $ $95$ $17$ ${}^{63}\mathrm {Ni}$ Mag spect OHSHIMA 1993 $ <1.0 $ $95$ 10$-$24 ${}^{63}\mathrm {Ni}$ Mag spect KAWAKAMI 1992 $ \text{<0.9 - 2.5} $ $90$ $1200 - 6800$ ${}^{20}\mathrm {F}$ beta spectrum 10 DEUTSCH 1990 $ <8 $ $90$ $80$ ${}^{35}\mathrm {S}$ Mag spect 11 APALIKOV 1985 $ <1.5 $ $90$ $60$ ${}^{35}\mathrm {S}$ Mag spect APALIKOV 1985 $ <3.0 $ $90$ 5$-$50 Mag spect MARKEY 1985 $ <0.62 $ $90$ $48$ ${}^{35}\mathrm {S}$ Si(Li) OHI 1985 $ <0.90 $ $90$ $30$ ${}^{35}\mathrm {S}$ Si(Li) OHI 1985 $ <4 $ $90$ $140$ ${}^{64}\mathrm {Cu}$ Mag spect 12 SCHRECKENBACH 1983 $ <8 $ $90$ $440$ ${}^{64}\mathrm {Cu}$ Mag spect 12 SCHRECKENBACH 1983 $ <100 $ $90$ $0.1 - 3000$ THEO 13 SHROCK 1980 $ <0.1 $ $68$ $80$ THEO 14 SHROCK 1980 1  TRINCZEK 2003 is a search for admixture of heavy neutrino to ${{\mathit \nu}_{{{e}}}}$, in contrast to ${{\overline{\mathit \nu}}_{{{e}}}}$ used in many other searches. Full kinematic reconstruction of the neutrino momentum by use of a magneto optical trap. 2  GALEAZZI 2001 use an cryogenic microcalorimeter to search for mass $50 - 1000$ eV neutrino admixtures using the ${}^{187}\mathrm {Re}$ beta spectrum with 2.4 keV endpoint. They derive limits for the admixture of heavy neutrinos, ranging from $9 \times 10^{-3}$ for mass 1 keV to $0.116$ for mass 100 eV. This is a significant improvement with respect to HIDDEMANN 1995, especially for masses below $\sim{}$500 MeV, where the limit is about a factor of $\sim{}$2 higher. 3  HOLZSCHUH 2000 use an iron-free $\beta ~$spectrometer to measure the ${}^{35}\mathrm {S}$ $\beta $ decay spectrum. An analysis of the spectrum in the energy range $56 - 173~$keV is used to derive limits for the admixture of heavy neutrinos. This extends the range of neutrino masses explored in HOLZSCHUH 1999. 4  DRAGOUN 1999 analyze the $\beta ~$decay spectrum of ${}^{241}\mathrm {Pu}$ in the energy range $0.2 - 9.2$ keV to derive limits for the admixture of heavy neutrinos. It is not competitive with HOLZSCHUH 1999. 5  HOLZSCHUH 1999 use an iron-free $\beta ~$spectrometer to measure the ${}^{63}\mathrm {Ni}\beta $ decay spectrum. An analysis of the spectrum in the energy rage $33 - 67.8$ keV is used to derive limits for the admixture of heavy neutrinos. 6  HINDI 1998 obtain a limit on heavy neutrino admixture from EC decay of ${}^{37}\mathrm {Ar}$ by measuring the time-of-flight distribution of the recoiling ions in coincidence with x-rays or Auger electrons. The authors report upper limit for $\vert \mathit U_{{{\mathit e}}\mathit x}\vert ^2$ of $\approx{}3\%$ for ${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$=500 keV, 1$\%$ for ${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$=550 keV, 2$\%$ for ${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$=600 keV, and 4$\%$ for ${\mathit m}_{{{\mathit x}}}$=650 keV. Their reported limits for ${\mathit m}_{{{\mathit \nu}_{{{x}}}}}{}\leq{}450$ keV are inferior to the limits of SCHRECKENBACH 1983. 7  In the beta spectrum from tritium $\beta $ decay nonvanishing or mixed ${\mathit m}_{{{\overline{\mathit \nu}}_{{{1}}}}}$ state in the mass region $0.01 - 4~$keV. For ${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$ $<1~$keV, their upper limit on $\vert \mathit U_{{{\mathit e}}\mathit x}\vert ^2$ becomes less 8  KALBFLEISCH 1993 extends the 17 keV neutrino search of BAHRAN 1992, using an improved proportional chamber to which a small amount of ${}^{3}\mathrm {H}$ is added. Systematics are significantly reduced, allowing for an improved upper limit. The authors give a 99$\%$ confidence limit on $\vert \mathit U_{{{\mathit e}}\mathit x}\vert ^2$ as a function of ${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$ in the range from $13.5$ keV to $17.5$ keV. See also the related papers BAHRAN 1993, BAHRAN 1993B, and BAHRAN 1995 on theoretical aspects of beta spectra and fitting methods for heavy neutrinos. 9  MORTARA 1993 limit is from study using a high-resolution solid-state detector with a superconducting solenoid. The authors note that ``The sensitivity to neutrino mass is verified by measurement with a mixed source of ${}^{35}\mathrm {S}$ and ${}^{14}\mathrm {C}$, which artificially produces a distortion in the beta spectrum similar to that expected from the massive neutrino.'' 10  DEUTSCH 1990 search for emission of heavy ${{\overline{\mathit \nu}}_{{{e}}}}$ in super-allowed beta decay of ${}^{20}\mathrm {F}$ by spectral analysis of the electrons. 11  This limit was taken from the figure 3 of APALIKOV 1985; the text gives a more restrictive limit of $1.7 \times 10^{-3}$ at CL = 90$\%$. 12  SCHRECKENBACH 1983 is a combined measurement of the ${{\mathit \beta}^{+}}$ and ${{\mathit \beta}^{-}}$ spectrum. 13  SHROCK 1980 was a retroactive analysis of data on several superallowed $\beta $ decays to search for kinks in the Kurie plot. 14  Application of test to search for kinks in $\beta $ decay Kurie plots.

References