38 research outputs found
Search for astronomical neutrinos from blazar TXS 0506+056 in super-kamiokande
We report a search for astronomical neutrinos in the energy region from several GeV to TeV in the direction of the blazar TXS 0506+056 using the Super-Kamiokande detector following the detection of a 100 TeV neutrinos from the same location by the IceCube collaboration. Using Super-Kamiokande neutrino data across several data samples observed from 1996 April to 2018 February we have searched for both a total excess above known backgrounds across the entire period as well as localized excesses on smaller timescales in that interval. No significant excess nor significant variation in the observed event rate are found in the blazar direction. Upper limits are placed on the electron- and muon-neutrino fluxes at the 90% confidence level as 6.0 Ă 10â7 and 4.5 Ă 10â7â9.3 Ă 10â10 [erg cmâ2 sâ1], respectively
Sensitivity of super-kamiokande with gadolinium to low energy antineutrinos from pre-supernova emission
Supernova detection is a major objective of the Super-Kamiokande (SK) experiment. In the next stage of SK (SK-Gd), gadolinium (Gd) sulfate will be added to the detector, which will improve the ability of the detector to identify neutrons. A core-collapse supernova (CCSN) will be preceded by an increasing flux of neutrinos and antineutrinos, from thermal and weak nuclear processes in the star, over a timescale of hours; some of which may be detected at SK-Gd. This could provide an early warning of an imminent CCSN, hours earlier than the detection of the neutrinos from core collapse. Electron antineutrino detection will rely on inverse beta decay events below the usual analysis energy threshold of SK, so Gd loading is vital to reduce backgrounds while maximizing detection efficiency. Assuming normal neutrino mass ordering, more than 200 events could be detected in the final 12 hr before core collapse for a 15â25 solar mass star at around 200 pc, which is representative of the nearest red supergiant to Earth, α-Ori (Betelgeuse). At a statistical false alarm rate of 1 per century, detection could be up to 10 hr before core collapse, and a pre-supernova star could be detected by SK-Gd up to 600 pc away. A pre-supernova alert could be provided to the astrophysics community following gadolinium loading
Search for neutrinos in coincidence with gravitational wave events from the LIGOâVirgo O3a observing run with the Super-Kamiokande detector
The Super-Kamiokande detector can be used to search for neutrinos in time coincidence with gravitational waves detected by the LIGOâVirgo Collaboration (LVC). Both low-energy (7â100 MeV) and high-energy (0.1â105 GeV) samples were analyzed in order to cover a very wide neutrino spectrum. Follow-ups of 36 (out of 39) gravitational waves reported in the GWTC-2 catalog were examined; no significant excess above the background was observed, with 10 (24) observed neutrinos compared with 4.8 (25.0) expected events in the high-energy (low-energy) samples. A statistical approach was used to compute the significance of potential coincidences. For each observation, p-values were estimated using neutrino direction and LVC sky map; the most significant event (GW190602_175927) is associated with a post-trial p-value of 7.8% (1.4Ï). Additionally, flux limits were computed independently for each sample and by combining the samples. The energy emitted as neutrinos by the identified gravitational wave sources was constrained, both for given flavors and for all flavors assuming equipartition between the different flavors, independently for each trigger and by combining sources of the same nature
Supernova model discrimination with hyper-kamiokande
Core-collapse supernovae are among the most magnificent events in the observable universe. They produce many of the chemical elements necessary for life to exist and their remnants - neutron stars and black holes - are interesting astrophysical objects in their own right. However, despite millennia of observations and almost a century of astrophysical study, the explosion mechanism of core-collapse supernovae is not yet well understood. Hyper-Kamiokande is a next-generation neutrino detector that will be able to observe the neutrino flux from the next galactic core-collapse supernova in unprecedented detail. We focus on the first 500 ms of the neutrino burst, corresponding to the accretion phase, and use a newly-developed, high-precision supernova event generator to simulate Hyper-Kamiokande's response to five different supernova models. We show that Hyper-Kamiokande will be able to distinguish between these models with high accuracy for a supernova at a distance of up to 100 kpc. Once the next galactic supernova happens, this ability will be a powerful tool for guiding simulations toward a precise reproduction of the explosion mechanism observed in nature
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Search for proton decay into three charged leptons in 0.37 megaton-years exposure of the Super-Kamiokande
A search for proton decay into three charged leptons has been performed by using 0.37 Mton·years of data collected in Super-Kamiokande. All possible combinations of electrons, muons, and their antiparticles consistent with charge conservation were considered as decay modes. No significant excess of events has been found over the background, and lower limits on the proton lifetime divided by the branching ratio have been obtained. The limits range between 9.2Ă1033 and 3.4Ă1034 years at 90% confidence level, improving by more than an order of magnitude upon limits from previous experiments. A first limit has been set for the pâÎŒ-e+e+ mode
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The Hyper-Kamiokande Experiment -- Snowmass LOI
Hyper-Kamiokande is the next generation underground water Cherenkov detector
that builds on the highly successful Super-Kamiokande experiment. The detector
which has an 8.4~times larger effective volume than its predecessor will be
located along the T2K neutrino beamline and utilize an upgraded J-PARC beam
with 2.6~times beam power. Hyper-K's low energy threshold combined with the
very large fiducial volume make the detector unique, that is expected to
acquire an unprecedented exposure of 3.8~Mtonyear over a period of
20~years of operation. Hyper-Kamiokande combines an extremely diverse science
program including nucleon decays, long-baseline neutrino oscillations,
atmospheric neutrinos, and neutrinos from astrophysical origins. The scientific
scope of this program is highly complementary to liquid-argon detectors for
example in sensitivity to nucleon decay channels or supernova detection modes.
Hyper-Kamiokande construction has started in early 2020 and the experiment is
expected to start operations in 2027. The Hyper-Kamiokande collaboration is
presently being formed amongst groups from 19 countries including the United
States, whose community has a long history of making significant contributions
to the neutrino physics program in Japan. US physicists have played leading
roles in the Kamiokande, Super-Kamiokande, EGADS, K2K, and T2K programs