J. Shirai

High sensitivity search for a 17 keV neutrino. Negative indication with an upper limit of 0.095

Abstract We have performed a search for a 17 keV neutrino by looking for a kink in the 63 Ni β-spectrum near the expected energy threshold. Using a large number of events (2.4 × 10 9 ) accumulated in a narrow energy region with the INS iron-free π √2 β -spectrometer, we obtain a mixing strength of [1.8±3.3(stat.)±3.3(syst.)]×10 −4 , and no indication of the presence of a 17 keV neutrino with the order of 1% mixing. We set an upper limit of 0.095% for the admixture of a neutrino with a mass of 17 keV and of 0.1% with a mass range of 10–24 keV, at the 95% confidence level.

A Study of charged D* production in e+ e- annihilation at an average center-of-mass energy of 58-GeV

Abstract We have studied the production of charged D ∗ mesons in e + e − annihilation at an average center-of-mass energy of 58.0 GeV. Charged D ∗ mesons were identified using two independent methods; the mass-difference method and the detection of the low transverse-momentum pion. The forward-backward asymmetry of the charm quark production was measured to be A c = −0.61±0.13(stat.)±0.08(syst.). The cross section of inclusive D ∗ production was found to be σ(e + e − →D ∗ ± +X) = 24.5 ± 5.3 ( stat. )±3.0( syst. ) pb. If we assume the standard model prediction for the charm quark production, we obtain the branching ratio for the charm quark to produce a charged D ∗ meson to be Br (c→D ∗+ + X) = (22±5( stat. )±3( syst. ))% .

Measurement of the reactionse+e−→μ+μ− ande+e−→τ+τ− between\(\sqrt s = 50\) and 60.8 GeV

AbstractThe angular distributions of the reactione+e−→μ+μ− ande+e+→τ+τ− have been measured between

Measurement of open charm production in two-photon processes with detection of electron-inclusive events

\sqrt s = 50

Search for heavy neutral spinless particles using e+e− → e+e− and e+e− → γγ reactions in the CM energy range between 54 and 64 GeV

and 60.8 GeV with the VENUS detector at TRISTAN. The average total cross section and the forward-backward charge asymmetry for μ-pair production are observed to be 28.3±1.4±0.8 pb and (−29.0−4.8+5.0±0.5)%, and those for τ-pair production are 27.6±1.7±1.0 pb and (−32.8−6.2+6.4±1.5)% at

Measurement of τ polarization in e+e- annihilation at √s = 58 GeV

\langle \sqrt s \rangle