53 research outputs found
The T2K ND280 Off-Axis Pi-Zero Detector
The Pi-Zero detector (P{\O}D) is one of the subdetectors that makes up the
off-axis near detector for the Tokai-to-Kamioka (T2K) long baseline neutrino
experiment. The primary goal for the P{\O}D is to measure the relevant cross
sections for neutrino interactions that generate pi-zero's, especially the
cross section for neutral current pi-zero interactions, which are one of the
dominant sources of background to the electron neutrino appearance signal in
T2K. The P{\O}D is composed of layers of plastic scintillator alternating with
water bags and brass sheets or lead sheets and is one of the first detectors to
use Multi-Pixel Photon Counters (MPPCs) on a large scale.Comment: 17 pages, submitted to NIM
Evidence for the Appearance of Atmospheric Tau Neutrinos in Super-Kamiokande
Super-Kamiokande atmospheric neutrino data were fit with an unbinned maximum
likelihood method to search for the appearance of tau leptons resulting from
the interactions of oscillation-generated tau neutrinos in the detector.
Relative to the expectation of unity, the tau normalization is found to be
1.42 \pm 0.35 \ (stat) {\}^{+0.14}_{-0.12}\ (syst) excluding the
no-tau-appearance hypothesis, for which the normalization would be zero, at the
3.8 level. We estimate that 180.1 \pm 44.3\ (stat)
{\}^{+17.8}_{-15.2}\ (syst) tau leptons were produced in the 22.5 kton
fiducial volume of the detector by tau neutrinos during the 2806 day running
period. In future analyses, this large sample of selected tau events will allow
the study of charged current tau neutrino interaction physics with oscillation
produced tau neutrinos.Comment: 7 pages, 4 figures. This is the version as published in Physical
Review Letters including the supplemental figure. A typographical error in
the description of figure 3 is also correcte
Search for Differences in Oscillation Parameters for Atmospheric Neutrinos and Antineutrinos at Super-Kamiokande
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 (dm2bar,
sin2 2 thetabar) = (2.0x10^-3 eV^2, 1.0) and is consistent with the overall
Super-K measurement.Comment: 6 pages, 4 figures. Figure update
Atmospheric neutrino oscillation analysis with sub-leading effects in Super-Kamiokande I, II, and III
We present a search for non-zero theta_{13} and deviations of sin^2
theta_{23} from 0.5 in the oscillations of atmospheric neutrino data from
Super-Kamiokande -I, -II, and -III. No distortions of the neutrino flux
consistent with non-zero theta_{13} are found and both neutrino mass hierarchy
hypotheses are in agreement with the data. The data are best fit at Delta m^2 =
2.1 x 10^-3 eV^2, sin^2 theta_{13} = 0.0, and sin^2 theta_{23} =0.5. In the
normal (inverted) hierarchy theta_{13} and Delta m^2 are constrained at the
one-dimensional 90% C.L. to sin^2 theta_{13} < 0.04 (0.09) and 1.9 (1.7) x
10^-3 < Delta m^2 < 2.6 (2.7) x 10^-3 eV^2. The atmospheric mixing angle is
within 0.407 <= sin^2 theta_{23} <= 0.583 at 90% C.L.Comment: 17 Pages, 14 figures. To be submitted to Phys. Rev. D Minor update to
text after referee comments. Figures modified for better grayscale printing
Solar neutrino results in Super-Kamiokande-III
The results of the third phase of the Super-Kamiokande solar neutrino
measurement are presented and compared to the first and second phase results.
With improved detector calibrations, a full detector simulation, and improved
analysis methods, the systematic uncertainty on the total neutrino flux is
estimated to be ?2.1%, which is about two thirds of the systematic uncertainty
for the first phase of Super-Kamiokande. The observed 8B solar flux in the 5.0
to 20 MeV total electron energy region is 2.32+/-0.04 (stat.)+/-0.05 (sys.)
*10^6 cm^-2sec^-1, in agreement with previous measurements. A combined
oscillation analysis is carried out using SK-I, II, and III data, and the
results are also combined with the results of other solar neutrino experiments.
The best-fit oscillation parameters are obtained to be sin^2 {\theta}12 =
0.30+0.02-0.01(tan^2 {\theta}12 = 0.42+0.04 -0.02) and {\Delta}m2_21 =
6.2+1.1-1.9 *10^-5eV^2. Combined with KamLAND results, the best-fit oscillation
parameters are found to be sin^2 {\theta}12 = 0.31+/-0.01(tan^2 {\theta}12 =
0.44+/-0.03) and {\Delta}m2_21 = 7.6?0.2*10^-5eV^2 . The 8B neutrino flux
obtained from global solar neutrino experiments is
5.3+/-0.2(stat.+sys.)*10^6cm^-2s^-1, while the 8B flux becomes
5.1+/-0.1(stat.+sys.)*10^6cm^-2s^-1 by adding KamLAND result. In a three-flavor
analysis combining all solar neutrino experiments, the upper limit of sin^2
{\theta}13 is 0.060 at 95% C.L.. After combination with KamLAND results, the
upper limit of sin^2 {\theta}13 is found to be 0.059 at 95% C.L..Comment: 19 pages, 33 figures in the main text. The appendix section on errata
is added in v
An Indirect Search for WIMPs in the Sun using 3109.6 days of upward-going muons in Super-Kamiokande
We present the result of an indirect search for high energy neutrinos from
WIMP annihilation in the Sun using upward-going muon (upmu) events at
Super-Kamiokande. Datasets from SKI-SKIII (3109.6 days) were used for the
analysis. We looked for an excess of neutrino signal from the Sun as compared
with the expected atmospheric neutrino background in three upmu categories:
stopping, non-showering, and showering. No significant excess was observed. The
90% C.L. upper limits of upward-going muon flux induced by WIMPs of 100
GeV/c were 6.4 cm sec and 4.0
cm sec for the soft and hard annihilation channels, respectively.
These limits correspond to upper limits of 4.5 cm and
2.7 cm for spin-dependent WIMP-nucleon scattering cross
sections in the soft and hard annihilation channels, respectively.Comment: Add journal reference. Also fixed typo and cosmetic things in the old
draf
Search for Astrophysical Neutrino Point Sources at Super-Kamiokande
It has been hypothesized that large fluxes of neutrinos may be created in
astrophysical "cosmic accelerators." The primary background for a search for
astrophysical neutrinos comes from atmospheric neutrinos, which do not exhibit
the pointlike directional clustering that characterizes a distant astrophysical
signal. We perform a search for neutrino point sources using the upward-going
muon data from three phases of operation (SK-I, SK-II, and SK-III) spanning
2623 days of live time taken from April 1, 1996 to August 11, 2007. The search
looks for signals from suspected galactic and extragalactic sources, transient
sources, and unexpected sources. We find interesting signatures from two
objects--RX J1713.7-3946 (97.5% CL) and GRB 991004D (95.3% CL)--but the
signatures lack compelling statistical significance given trial factors. We set
limits on the flux and fluence of neutrino point sources above energies of 1.6
GeV
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