Abstract
The next-generation experiment JUNO will determine the solar oscillation parameters - sin
2
θ
12
and
Δ
m
21
2
- with great accuracy, in addition to measuring sin
2
θ
13
,
Δ
m
31
2
and the ...mass ordering. In parallel, the continued study of solar neutrinos at Hyper-Kamiokande will provide complementary measurements in the solar sector. Here we address the expected sensitivity to non-universal and flavour-changing non-standard interactions (NSI) with d-type quarks from the combination of these two future neutrino experiments. We also show the robustness of the measurement of the solar parameters and sin
2
θ
12
and
Δ
m
21
2
in the presence of NSI and comment on the enduring potential viability of the LMA-D solution.
The next-generation neutrino experiment JUNO will determine the solar oscillation parameters - \(\sin^2 \theta_{12}\) and \(\Delta m^2_{21}\) - with great accuracy, in addition to measuring ...\(\sin^2\theta_{13}\), \(\Delta m^2_{31}\), and the mass ordering. In parallel, the continued study of solar neutrinos at Hyper-Kamiokande will provide complementary measurements in the solar sector. In this paper, we address the expected sensitivity to non-universal and flavour-changing non-standard interactions (NSI) with \(d\)-type quarks from the combination of these two future neutrino experiments. We also show the robustness of their measurements of the solar parameters \(\sin^2 \theta_{12}\) and \(\Delta m^2_{21}\) in the presence of NSI. We study the impact of the exact experimental configuration of the Hyper-Kamiokande detector, and conclude it is of little relevance in this scenario. Finally, we find that the LMA-D solution is expected to be present if no additional input from non-oscillation experiments is considered.
We report the results of a neutrino search in Super-Kamiokande (SK) for coincident signals with the first detected gravitational wave (GW) produced by a binary neutron-star merger, GW170817, which ...was followed by a short gamma-ray burst, GRB170817A, and a kilonova/macronova. We searched for coincident neutrino events in the range from 3.5 MeV to ∼100 PeV, in a time window 500 s around the gravitational wave detection time, as well as during a 14-day period after the detection. No significant neutrino signal was observed for either time window. We calculated 90% confidence level upper limits on the neutrino fluence for GW170817. From the upward-going-muon events in the energy region above 1.6 GeV, the neutrino fluence limit is 16.0 − 0.6 + 0.7 ( 21.3 − 0.8 + 1.1 ) cm−2 for muon neutrinos (muon antineutrinos), with an error range of 5° around the zenith angle of NGC4993, and the energy spectrum is under the assumption of an index of −2. The fluence limit for neutrino energies less than 100 MeV, for which the emission mechanism would be different than for higher-energy neutrinos, is also calculated. It is 6.6 × 107 cm−2 for anti-electron neutrinos under the assumption of a Fermi-Dirac spectrum with average energy of 20 MeV.
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 \pm 9 \mu s.
Non-Standard Interactions (NSI) between neutrinos and matter affect the neutrino flavor oscillations. Due to the high matter density in the core of the Sun, solar neutrinos are suited to probe these ...interactions. Using the \(277\) kton-yr exposure of Super-Kamiokande to \(^{8}\)B solar neutrinos, we search for the presence of NSI. Our data favors the presence of NSI with down quarks at 1.8\(\sigma\), and with up quarks at 1.6\(\sigma\), with the best fit NSI parameters being (\(\epsilon_{11}^{d},\epsilon_{12}^{d}\)) = (-3.3, -3.1) for \(d\)-quarks and (\(\epsilon_{11}^{u},\epsilon_{12}^{u}\)) = (-2.5, -3.1) for \(u\)-quarks. After combining with data from the Sudbury Neutrino Observatory and Borexino, the significance increases by 0.1\(\sigma\).
Due to a very low production rate of electron anti-neutrinos (\(\bar{\nu}_e\)) via nuclear fusion in the Sun, a flux of solar \(\bar{\nu}_e\) is unexpected. An appearance of \(\bar{\nu}_e\) in solar ...neutrino flux opens a new window for the new physics beyond the standard model. In particular, a spin-flavor precession process is expected to convert an electron neutrino into an electron anti-neutrino (\({\nu_e\to\bar{\nu}_e}\)) when neutrino has a finite magnetic moment. In this work, we have searched for solar \(\bar{\nu}_e\) in the Super-Kamiokande experiment, using neutron tagging to identify their inverse beta decay signature. We identified 78 \(\bar{\nu}_e\) candidates for neutrino energies of 9.3 to 17.3 MeV in 2970.1 live days with a fiducial volume of 22.5 kiloton water (183.0 kton\(\cdot\)year exposure). The energy spectrum has been consistent with background predictions and we thus derived a 90% confidence level upper limit of \({4.7\times10^{-4}}\) on the \(\nu_e\to\bar{\nu}_e\) conversion probability in the Sun. We used this result to evaluate the sensitivity of future experiments, notably the Super-Kamiokande Gadolinium (SK-Gd) upgrade.
The Super-Kamiokande detector can be used to search for neutrinos in time coincidence with gravitational waves detected by the LIGO-Virgo Collaboration (LVC). Both low-energy (\(7-100\) MeV) and ...high-energy (\(0.1-10^5\) 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 \(7.8\%\) (\(1.4\sigma\)). 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.
A search for neutrinos produced in coincidence with Gamma-Ray Bursts(GRB) was conducted with the Super-Kamiokande (SK) detector. Between December 2008 and March 2017, the Gamma-ray Coordinates ...Network recorded 2208 GRBs that occurred during normal SK operation. Several time windows around each GRB were used to search for coincident neutrino events. No statistically significant signal in excess of the estimated backgrounds was detected. The \(\bar\nu_e\) fluence in the range from 8 MeV to 100 MeV in positron total energy for \(\bar\nu_e+p\rightarrow e^{+}+n\) was found to be less than \(\rm 5.07\times10^5\) cm\(^{-2}\) per GRB in 90\% C.L. Upper bounds on the fluence as a function of neutrino energy were also obtained.
We present a search for an excess of neutrino interactions due to dark matter in the form of Weakly Interacting Massive Particles (WIMPs) annihilating in the galactic center or halo based on the data ...set of Super-Kamiokande-I, -II, -III and -IV taken from 1996 to 2016. We model the neutrino flux, energy, and flavor distributions assuming WIMP self-annihilation is dominant to \(\nu \overline{\nu}\), \(\mu^+\mu^-\), \(b\overline{b}\), or \(W^+W^-\). The excess is in comparison to atmospheric neutrino interactions which are modeled in detail and fit to data. Limits on the self-annihilation cross section \(\langle \sigma_{A} V \rangle\) are derived for WIMP masses in the range 1 GeV to 10 TeV, reaching as low as \(9.6 \times10^{-23}\) cm\(^3\) s\(^{-1}\) for 5 GeV WIMPs in \(b\bar b\) mode and \(1.2 \times10^{-24}\) cm\(^3\) s\(^{-1}\) for 1 GeV WIMPs in \(\nu \bar \nu\) mode. The obtained sensitivity of the Super-Kamiokande detector to WIMP masses below several tens of GeV is the best among similar indirect searches to date.
A search for proton decay into three charged leptons has been performed by using 0.37\(\,\)Mton\(\cdot\)years of data collected in Super-Kamiokande. All possible combinations of electrons, muons and ...their anti-particles 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 \(9.2\times10^{33}\) to \(3.4\times10^{34}\) 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 \(p\rightarrow\mu^-e^+e^+\) mode.
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