49 research outputs found
Test of Lorentz invariance with atmospheric neutrinos
Artículo escrito por un elevado número de autores, solo se referencian el que aparece en primer lugar, el nombre del grupo de colaboración, si le hubiere, y los autores pertenecientes a la UAMA search for neutrino oscillations induced by Lorentz violation has been performed using 4,438 live-days of Super-Kamiokande atmospheric neutrino data. The Lorentz violation is included in addition to standard three-flavor oscillations using the nonperturbative standard model extension (SME), allowing the use of the full range of neutrino path lengths, ranging from 15 to 12,800 km, and energies ranging from 100 MeV to more than 100 TeV in the search. No evidence of Lorentz violation was observed, so limits are set on the renormalizable isotropic SME coefficients in the eμ, μτ, and eτ sectors, improving the existing limits by up to 7 orders of magnitude and setting limits for the first time in the neutrino μτ sector of the SMEWe would like to thank A. Kostelecky for his advice and support and we are grateful to J. S. Diaz for working closely with us to calculate and implement the Lorentz-violating oscillation probabilities. The authors gratefully acknowledge the cooperation of the Kamioka Mining and Smelting Company. Super-K has been built and operated from funds provided by the Japanese Ministry of Education, Culture, Sports, Science and Technology, the U.S. Department of Energy, and the U.S. National Science Foundation. This work was partially supported by the Research Foundation of Korea (BK21 and KNRC), the Korean Ministry of Science and Technology, the National Science Foundation of China, the European Union FP7 (DS laguna-lbno PN- 284518 and ITN invisibles GA-2011-289442), the National Science and Engineering Research Council (NSERC) of Canada, and the Scinet and Westgrid consortia of Compute Canad
Limits on sterile neutrino mixing using atmospheric neutrinos in Super-Kamiokande
Artículo escrito por un elevado número de autores, solo se referencian el que aparece en primer lugar, el nombre del grupo de colaboración, si le hubiere, y los autores pertenecientes a la UAMWe present limits on sterile neutrino mixing using 4,438 live-days of atmospheric neutrino data from the Super-Kamiokande experiment. We search for fast oscillations driven by an eV2-scale mass splitting and for oscillations into sterile neutrinos instead of tau neutrinos at the atmospheric mass splitting. When performing both of these searches we assume that the sterile mass splitting is large, allowing sin2(Δm2L/4E) to be approximated as 0.5, and we assume that there is no mixing between electron neutrinos and sterile neutrinos (|Ue4|2=0). No evidence of sterile oscillations is seen and we limit |Uμ4|2 to less than 0.041 and |Uτ4|2 to less than 0.18 for Δm2>0.1eV2 at the 90% C.L. in a 3+1 framework. The approximations that can be made with atmospheric neutrinos allow these limits to be easily applied to 3+N models, and we provide our results in a generic format to allow comparisons with other sterile neutrino modelsThe authors gratefully acknowledge the cooperation of the Kamioka Mining and Smelting Company. Super-K has been built and operated from funds provided by the Japanese Ministry of Education, Culture, Sports, Science and Technology, the U.S. Department of Energy, and the U.S. National Science Foundation. This work was partially supported by the Research Foundation of Korea (BK21 and KNRC), the Korean Ministry of Science and Technology, the National Science Foundation of China, the European Union FP7 (DS laguna-lbno PN- 284518 and ITN invisibles GA-2011-289442) the National Science and Engineering Research Council (NSERC) of Canada, and the Scinet and Westgrid consortia of Compute Canad
Search for neutrinos in Super-Kamiokande associated with gravitational-wave events GW150914 and GW151226
Astrophysical Journal Letters 830.1 (2016): L11 reproduced by permission of the AASWe report the results from a search in Super-Kamiokande for neutrino signals coincident with the first detected gravitational-wave events, GW150914 and GW151226, as well as LVT151012, using a neutrino energy range from 3.5 MeV to 100 PeV. We searched for coincident neutrino events within a time window of ±500 s around the gravitational-wave detection time. Four neutrino candidates are found for GW150914, and no candidates are found for GW151226. The remaining neutrino candidates are consistent with the expected background events. We calculated the 90% confidence level upper limits on the combined neutrino fluence for both gravitational-wave events, which depends on event energy and topologies. Considering the upward-going muon data set (1.6 GeV-100 PeV), the neutrino fluence limit for each gravitational-wave event is 14-37 (19-50) cm-2 for muon neutrinos (muon antineutrinos), depending on the zenith angle of the event. In the other data sets, the combined fluence limits for both gravitational-wave events range from 2.4 ×104 to 7.0 ×109 cm-2The Super-Kamiokande experiment has been built and operated from funding by the Japanese Ministry of Education, Culture, Sports, Science and Technology, the U.S. Department of Energy, and the U.S. National Science Foundation. Some of us have been supported by funds from the Korean Research Foundation (BK21 and KNRC), the National Research Foundation of Korea (NRF-20110024009), the European Union (H2020 RISE-GA641540-SKPLUS), the Japan Society for the Promotion of Science, the National Natural Science Foundation of China under grant No. 11235006, and the Scinet and Westgrid consortia of Compute Canad
Indirect search for dark matter from the Galactic Center and halo with the Super-Kamiokande detector
Artículo escrito por un elevado número de autores, solo se referencian el que aparece en primer lugar, el nombre del grupo de colaboración, si le hubiere, y los autores pertenecientes a la UA
Diffuse supernova neutrino background search at Super-Kamiokande
Artículo escrito por un elevado número de autores, solo se referencian el que aparece en primer lugar, el nombre del grupo de colaboración, si le hubiere, y los autores pertenecientes a la UAMWe have conducted a new search for the diffuse supernova neutrino background (DSNB) flux at Super-Kamiokande (SK), with a 22.5 × 2970-kton · day exposure from its fourth operational phase IV. With the new analysis we improve on the existing background reduction techniques and systematic uncertainties and take advantage of an improved neutron tagging algorithm to lower the energy threshold compared to the previous phases of SK. This allows for setting the world's most stringent upper limit on the extraterrestrial ν¯e flux, for neutrino energies below 31.3 MeV. The SK-IV results are combined with the ones from the first three phases of SK to perform a joint analysis using 22.5 × 5823 kton·days of data. This analysis has the world's best sensitivity to the DSNB ν¯e flux, comparable to the predictions from various models. For neutrino energies larger than 17.3 MeV, the new combined 90% CL upper limits on the DSNB ν¯e flux lie around 2.7 cm-2 · sec-1, strongly disfavoring the most optimistic predictions. Finally, potentialities of the gadolinium phase of SK and the future Hyper-Kamiokande experiment are discusse
A novel way of constraining WIMPs annihilations in the Sun: MeV neutrinos
Annihilation of dark matter particles accumulated in the Sun would produce a
flux of high-energy neutrinos whose prospects of detection in neutrino
telescopes and detectors have been extensively discussed in the literature.
However, for annihilations into Standard Model particles, there would also be a
flux of neutrinos in the MeV range from the decays at rest of muons and
positively charged pions. These low-energy neutrinos have never been considered
before and they open the possibility to also constrain dark matter annihilation
in the Sun into e+e-, mu+mu- or light quarks. Here we perform a detailed
analysis using the recent Super-Kamiokande data in the few tens of MeV range to
set limits on the WIMP-nucleon scattering cross section for different
annihilation channels and computing the evaporation rate of WIMPs from the Sun
for all values of the scattering cross section in a consistent way.Comment: 26 pages, 7 figures. Substantial additions with further explanations.
Two significant improvements: in the calculation of the evaporation and
capture rates; and in the analysis of the SK data. Minor changes in the
conclusions. It matches published versio
Global neutrino data and recent reactor fluxes: status of three-flavour oscillation parameters
We present the results of a global neutrino oscillation data analysis within
the three-flavour framework. We include latest results from the MINOS
long-baseline experiment (including electron neutrino appearance as well as
anti-neutrino data), updating all relevant solar (SK II+III), atmospheric (SK
I+II+III) and reactor (KamLAND) data. Furthermore, we include a recent
re-calculation of the anti-neutrino fluxes emitted from nuclear reactors. These
results have important consequences for the analysis of reactor experiments and
in particular for the status of the mixing angle . In our
recommended default analysis we find from the global fit that the hint for
non-zero remains weak, at 1.8 for both neutrino mass
hierarchy schemes. However, we discuss in detail the dependence of these
results on assumptions concerning the reactor neutrino analysis.Comment: 15 pages, 10 figures and 2 tables, v2: corrected version, main
conclusions unchanged, references adde
Discrete symmetries and models of flavor mixing
Evidences of a discrete symmetry behind the pattern of lepton mixing are
analyzed. The program of "symmetry building" is outlined. Generic features and
problems of realization of this program in consistent gauge models are
formulated. The key issues include the flavor symmetry breaking, connection of
mixing and masses, {\it ad hoc} prescription of flavor charges, "missing"
representations, existence of new particles, possible accidental character of
the TBM mixing. Various ways are considered to extend the leptonic symmetries
to the quark sector and to reconcile them with Grand Unification. In this
connection the quark-lepton complementarity could be a viable alternative to
TBM. Observational consequences of the symmetries and future experimental tests
of their existence are discussed.Comment: 14 pages, 5 figures. Talk given at the Symposium "DISCRETE 2010", 6 -
11 December 2010, La Sapienza, Rome, Ital
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