A search for the appearance of tau neutrinos from nu(mu) <--> nu(tau) oscillations in the atmospheric neutrinos has been performed using 1489.2 days of atmospheric neutrino data from the ...Super-Kamiokande-I experiment. A best fit tau neutrino appearance signal of 138+/-48(stat)-32(+15)(syst) events is obtained with an expectation of 78+/-26(syst). The hypothesis of no tau neutrino appearance is disfavored by 2.4 sigma.
A search for the relic neutrinos from all past core-collapse supernovae was conducted using 1496 days of data from the Super-Kamiokande detector. This analysis looked for electron-type antineutrinos ...that had produced a positron with an energy greater than 18 MeV. In the absence of a signal, 90% C.L. upper limits on the total flux were set for several theoretical models; these limits ranged from 20 to 130 macro nu(e) cm(-2) s(-1). Additionally, an upper bound of 1.2 macro nu(e) cm(-2) s(-1) was set for the supernova relic neutrino flux in the energy region E(nu)>19.3 MeV.
We have investigated electronic structure evolution by cation substitution in Ba 3 − x Sr x Nb5 O15 by means of hard x-ray photoemission spectroscopy. Localization of Nb 4 d electrons manifests as ...spectral weight transfer from a coherent component at the Fermi level to an incoherent one at 1–2 eV below it. This behavior is similar to that of electron-doped SrTiO3 . On the other hand, Nb 3 d and 4 p core level spectra exhibit a screening effect with an energy scale of 1–2 eV by the coherent Nb 4 d electrons similar to 4 d electron systems near Mott transitions. The energy scale indicates that electron correlation is involved in the metal to insulator transition in the present system, although the Nb 4 d band is about 1/10 filled. The present results suggest a mechanism of electron localization due to atomic disorder and electron correlation.
We have studied a charge-orbital driven metal-insulator transition (MIT) in hollandite-type BaxTi8O16+δ by means of hard x-ray photoemission spectroscopy (HAXPES). The Ti 2p HAXPES indicates strong ...Ti3+/Ti4+ charge fluctuation in the metallic phase above the MIT temperature. The metallic phase is characterized by a power-law spectral function near the Fermi level which would be a signature of bad metal with non-Drude polaronic behavior. The power-law spectral shape is associated with the large Seebeck coefficient of the metallic phase in BaxTi8O16+δ.
In this article we review the discovery of atmospheric neutrino oscillation by the Super-Kamiokande experiment. This review outlines the sequence of observations and their associated publications ...that solved the atmospheric neutrino anomaly and established the existence of neutrino oscillations with nearly maximal mixing of muon neutrinos and tau neutrinos. We also discuss subsequent and ongoing studies that use atmospheric neutrinos to continue to reveal the nature of the neutrino.
We studied single crystals of orthorhombic Sr2VO4 containing spin-singlet dimers of V4+(3d1) and those with Ti or Nb substituted for V. We found that both Ti and Nb dopings induce the evolution of a ...Curie-Weiss component in the magnetic susceptibility, but the rate of evolution with doping is several times higher for Nb doping. We also found that Nb doping induces the conduction of d electrons. These results can be explained by the hybridization of the Nb 4d states with the 3d states of the neighboring V ions, possibly causing rearrangement of the d electron in the doubly degenerate e states in the V ion.
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