The trilepton nucleon decay modes p→e+νν and p→μ+νν violate |Δ(B-L)| by two units. Using data from a 273.4 kt yr exposure of Super-Kamiokande a search for these decays yields a fit consistent with no ...signal. Accordingly, lower limits on the partial lifetimes of τp→e+νν>1.7×10(32) years and τp→μ+νν>2.2×10(32) years at a 90% confidence level are obtained. These limits can constrain Grand Unified Theories which allow for such processes.
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We present the results of a search in the Super-Kamiokande (SK) detector for excesses of neutrinos with energies above a few GeV that are in the direction of the track events reported in IceCube. ...Data from all SK phases (SK-I through SK-IV) were used, spanning a period from 1996 April to 2016 April and corresponding to an exposure of 225 kiloton-years. We considered the 14 IceCube track events from a data set with 1347 livetime days taken from 2010 to 2014. We use Poisson counting to determine if there is an excess of neutrinos detected in SK in a 10° search cone (5° for the highest energy data set) around the reconstructed direction of the IceCube event. No significant excess was found in any of the search directions we examined. We also looked for coincidences with a recently reported IceCube multiplet event. No events were detected within a 500 s time window around the first detected event, and no significant excess was seen from that direction over the lifetime of SK.
Abstract
We present the development of neutron-tagging techniques in
Super-Kamiokande IV using a neural network analysis. The detection
efficiency of neutron capture on hydrogen is estimated to be ...26%,
with a mis-tag rate of 0.016 per neutrino event. The uncertainty of
the tagging efficiency is estimated to be 9.0%. Measurement of the
tagging efficiency with data from an Americium-Beryllium calibration
agrees with this value within 10%. The tagging procedure was
performed on 3,244.4 days of SK-IV atmospheric neutrino data,
identifying 18,091 neutrons in 26,473 neutrino events. The fitted
neutron capture lifetime was measured as 218±9 μs.
The observation of the recent electron neutrino appearance in a muon neutrino beam and the high-precision measurement of the mixing angle
$\theta _{13}$
have led to a re-evaluation of the physics ...potential of the T2K long-baseline neutrino oscillation experiment. Sensitivities are explored for CP violation in neutrinos, non-maximal
$\sin ^22\theta _{23}$
, the octant of
$\theta _{23}$
, and the mass hierarchy, in addition to the measurements of
$\delta _{{\rm CP}}$
,
$\sin ^2\theta _{23}$
, and
$\Delta m^2_{32}$
, for various combinations of
$\nu$
-mode and
$\bar {\nu }$
-mode data-taking.
With an exposure of
$7.8\times 10^{21}$
protons-on-target, T2K can achieve 1
$\sigma$
resolution of 0.050 (0.054) on
$\sin ^2\theta _{23}$
and
$0.040\ (0.045)\times 10^{-3}\,\rm {eV}^2$
on
$\Delta m^2_{32}$
for 100% (50%) neutrino beam mode running assuming
$\sin ^2\theta _{23}=0.5$
and
$\Delta m^2_{32} = 2.4\times 10^{-3}\,\hbox {eV}^2$
. T2K will have sensitivity to the CP-violating phase
$\delta _{\rm {CP}}$
at 90% C.L. or better over a significant range. For example, if
$\sin ^22\theta _{23}$
is maximal (i.e.
$\theta _{23}=45^\circ$
) the range is
$-115^\circ \lt \delta _{\rm {CP}}\lt -60^\circ$
for normal hierarchy and
$+50^\circ \lt \delta _{\rm {CP}}\lt +130^\circ$
for inverted hierarchy. When T2K data is combined with data from the NO
$\nu$
A experiment, the region of oscillation parameter space where there is sensitivity to observe a non-zero
$\delta _{{\rm CP}}$
is substantially increased compared to if each experiment is analyzed alone.
We report that upgraded electronics, improved water system dynamics, better calibration and analysis techniques allowed Super-Kamiokande-IV to clearly observe very low-energy B 8 solar neutrino ...interactions, with recoil electron kinetic energies as low as ~3.5 MeV . Super-Kamiokande-IV data-taking began in September of 2008; this paper includes data until February 2014, a total livetime of 1664 days. The measured solar neutrino flux is ( 2.308±0.020 ( stat ) -0.040+0.039 ( syst ) ) ×106 / ( cm2 sec ) assuming no oscillations. The observed recoil electron energy spectrum is consistent with no distortions due to neutrino oscillations. An extended maximum likelihood fit to the amplitude of the expected solar zenith angle variation of the neutrino-electron elastic scattering rate in SK-IV results in a day/night asymmetry of ( -3.6±1.6 ( stat ) ±0.6 ( syst ) ) % . The SK-IV solar neutrino data determine the solar mixing angle as sin2θ12=0.327-0.031+0.026 , all SK solar data (SK-I, SK-II, SK III and SK-IV) measures this angle to be sin2θ12=0.334-0.023+0.027 , the determined mass-squared splitting is Δ m212=4.8-0.8+1.5×10-5 eV2 .
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We present a search for differences in the oscillations of antineutrinos and neutrinos in the Super-Kamiokande-I, -II, and -III atmospheric neutrino sample. Under a two-flavor disappearance model ...with separate mixing parameters between neutrinos and antineutrinos, we find no evidence for a difference in oscillation parameters. Best-fit antineutrino mixing is found to be at ({Delta}m{sup 2},sin{sup 2}2{theta})= (2.0x10{sup -3} eV{sup 2},1.0) and is consistent with the overall Super-K measurement.
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