217 research outputs found
Te covered Si(001): a variable surface reconstruction
At a given temperature, clean and adatom covered silicon surfaces usually
exhibit well-defined reconstruction patterns. Our finite temperature ab-initio
molecular dynamics calculations show that the tellurium covered Si(001) surface
is an exception. Soft longitudinal modes of surface phonons due to the strongly
anharmonic potential of the bridged tellurium atoms prevent the reconstruction
structure from attaining any permanent, two dimensional periodic geometry. This
explains why experiments attempting to find a definite model for the
reconstruction have reached conflicting conclusions.Comment: 4 pages, 3 gif figure
Measurement of radon concentrations at Super-Kamiokande
Radioactivity from radon is a major background for observing solar neutrinos
at Super-Kamiokande. In this paper, we describe the measurement of radon
concentrations at Super-Kamiokande, the method of radon reduction, and the
radon monitoring system. The measurement shows that the current low-energy
event rate between 5.0 MeV and 6.5 MeV implies a radon concentration in the
Super-Kamiokande water of less than 1.4 mBq/m.Comment: 11 pages, 4 figure
Observation of the east-west anisotropy of the atmospheric neutrino flux
The east-west anisotropy, caused by the deflection of primary cosmic rays in
the Earth's magnetic field, is observed for the first time in the flux of
atmospheric neutrinos. Using a 45 kt-year exposure of the
Super-Kamiokande detector, 552 e-like and 633 mu-like horizontally-going
events are selected in the momentum range between 400 and 3000 MeV/c.
The azimuthal distribution of e-like and mu-like events agrees with the
expectation from atmospheric neutrino flux calculations that account for the
geomagnetic field, verifying that the geomagnetic field effects in the
production of atmospheric neutrinos in the GeV energy range are well
understood.Comment: 8 pages,3 figures revtex, submitted to PR
Study of Non-Standard Neutrino Interactions with Atmospheric Neutrino Data in Super-Kamiokande I and II
In this paper we study non-standard neutrino interactions as an example of
physics beyond the standard model using atmospheric neutrino data collected
during the Super-Kamiokande I(1996-2001) and II(2003-2005) periods. We focus on
flavor-changing-neutral-currents (FCNC), which allow neutrino flavor
transitions via neutral current interactions, and effects which violate lepton
non-universality (NU) and give rise to different neutral-current
interaction-amplitudes for different neutrino flavors. We obtain a limit on the
FCNC coupling parameter, varepsilon_{mu tau}, |varepsilon_{mu tau}|<1.1 x
10^{-2} at 90%C.L. and various constraints on other FCNC parameters as a
function of the NU coupling, varepsilon_{e e}. We find no evidence of
non-standard neutrino interactions in the Super-Kamiokande atmospheric data.Comment: 12 Pages, 14 figures. To be submitted to Phys. Rev.
Search for Matter-Dependent Atmospheric Neutrino Oscillations in Super-Kamiokande
We consider muon neutrino to tau neutrino oscillations in the context of the
Mass Varying Neutrino (MaVaN) model, where the neutrino mass can vary depending
on the electron density along the flight path of the neutrino. Our analysis
assumes a mechanism with dependence only upon the electron density, hence
ordinary matter density, of the medium through which the neutrino travels.
Fully-contained, partially-contained and upward-going muon atmospheric neutrino
data from the Super--Kamiokande detector, taken from the entire SK--I period of
1489 live days, are compared to MaVaN model predictions. We find that, for the
case of 2-flavor oscillations, and for the specific models tested, oscillation
independent of electron density is favored over density dependence. Assuming
maximal mixing, the best-fit case and the density-independent case do not
differ significantly.Comment: 6 pages, 1 figur
Search for Nucleon Decay into Charged Anti-lepton plus Meson in Super-Kamiokande I and II
Searches for a nucleon decay into a charged anti-lepton (e^+ or {\mu}^+) plus
a light meson ({\pi}^0, {\pi}^-, {\eta}, {\rho}^0, {\rho}^-, {\omega}) were
performed using the Super-Kamiokande I and II data. Twelve nucleon decay modes
were searched for. The total exposure is 140.9 kiloton \cdot years, which
includes a 91.7 kiloton \cdot year exposure (1489.2 live days) of
Super-Kamiokande-I and a 49.2 kiloton \cdot year exposure (798.6 live days) of
Super-Kamiokande-II. The number of candidate events in the data was consistent
with the atmospheric neutrino background expectation. No significant evidence
for a nucleon decay was observed in the data. Thus, lower limits on the nucleon
partial lifetime at 90% confidence level were obtained. The limits range from
3.6 \times 10^31 to 8.2 \times 10^33 years, depending on the decay modes.Comment: 25 pages, 18 figure
Solar neutrino measurements in Super-Kamiokande-I
The details of Super--Kamiokande--I's solar neutrino analysis are given.
Solar neutrino measurement in Super--Kamiokande is a high statistics collection
of B solar neutrinos via neutrino-electron scattering. The analysis method
and results of the 1496 day data sample are presented. The final oscillation
results for the data are also presented.Comment: 32pages, 57figures, submitted to Physical Review
Three flavor neutrino oscillation analysis of atmospheric neutrinos in Super-Kamiokande
We report on the results of a three-flavor oscillation analysis using
Super-Kamiokande~I atmospheric neutrino data, with the assumption of one mass
scale dominance (0). No significant flux change due to
matter effect, which occurs when neutrinos propagate inside the Earth for
0, has been seen either in a multi-GeV -rich sample
or in a -rich sample. Both normal and inverted mass hierarchy
hypotheses are tested and both are consistent with observation. Using
Super-Kamiokande data only, 2-dimensional 90 % confidence allowed regions are
obtained: mixing angles are constrained to and for the normal mass hierarchy. Weaker constraints,
and , are obtained
for the inverted mass hierarchy case.Comment: 7 figures, 3 table
A Measurement of Atmospheric Neutrino Flux Consistent with Tau Neutrino Appearance
A search for the appearance of tau neutrinos from \mutau 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.) (sys.) events is
obtained with an expectation of 78 26 (sys.). The hypothesis of no tau
neutrino appearance is disfavored by 2.4 sigma.Comment: 5 pages, 3 figures, 3 tables, submitted to PR
Labor markets and cultural values: Evidence from Japanese and American views about caregiving immigrants
One overlooked reason for the persistence of distinct cultural values across rich democracies, we argue, is a country's labor market structure. Parents seeking to position their children for long‐term success would do well to instill values consistent with requirements of the labor market in the country where their children are likely to work. To the extent that labor markets are fluid, as in the United States, parents should teach their children to be resourceful and creative. In countries like Japan with relatively rigid labor markets, where workers have one chance to land a long‐term contract with a leading company, parents instead should instill the values of hard work and respect for authority. We find evidence consistent with this argument in survey experiments about attitudes in the United States and Japan about the desirability of employing immigrants for care work, and what values the immigrant care workers should hold. We also find evidence of indirect norm creation. American and Japanese respondents prefer immigrants—not just caregiving immigrants—whose values align with their country's type of valued human capital
- …