Measurements of the atmospheric neutrino flux by Super-Kamiokande: Energy spectra, geomagnetic effects, and solar modulation

Abstract

2A comprehensive study of the atmospheric neutrino flux in the energy region from sub-GeV up to several TeV using the Super-Kamiokande water Cherenkov detector is presented in this paper. The energy and azimuthal spectra, and variation over time, of the atmospheric νe+νe and νµ+νµ fluxes are measured. The energy spectra are obtained using an iterative unfolding method by combining various event topologies with differing energy responses. The azimuthal spectra depending on energy and zenith angle, and their modulation by geomagnetic effects, are also studied. A predicted east-west asymmetry is observed in both the νe and νµ samples at 8.0 σ and 6.0 σ significance, respectively, and an indication that the asymmetry dipole angle changes depending on the zenith angle was seen at the 2.2 σ level. The measured energy and azimuthal spectra are consistent with the current flux models within the estimated systematic uncertainties. A study of the long-term correlation between the atmospheric neutrino flux and the solar magnetic activity cycle is performed, and a weak preference for a correlation was seen at the 1.1 σ level, using SK I-IV data spanning a 20 year period. For several particularly strong solar activity periods, corresponding to Forbush decrease events, no theoretical prediction is available but a deviation below the typical neutrino event rate is seen at the 2.4 σ level. The seasonal modulation of the neutrino flux is also examined, but the change in flux at the SK site is predicted to be negligible, and as expected no evidence for a seasonal correlation is seen.PACS numbers: 95.55.Vj

Detecting CNO solar neutrinos in next-generation xenon dark matter experiments

“…The result of this integration as a function of E ν is given in Fig 3, indicating the neutrino energy range that a xenon and argon detector with E R 3 keV and E R 25 keV (respectively) would be sensitive to. For comparison we also show the lowest energy channel (sub-GeV single-ring electron-like events) that Super-Kamiokande was sensitive to in their atmospheric neutrino analysis [16]. As indicated, Super-Kamiokande is sensitive to neutrinos 100 MeV for their fully-contained electron-like events.…”

“…CEνNS is a standard model neutral-current process whose differential cross . Also shown is the neutrino energy range above which Super-K is sensitive to [16].…”

Atmospheric Neutrino Results from Super-Kamiokande

“…Super-K recently published a direct measurement of atmospheric neutrino flux [2], with energy spectra measured in the range of 100 MeV to 10 TeV. Fig.1 shows the Super-K-measured neutrino fluxes as a function of the neutrino energy, and the ratio of data to oscillated HKKM11 model prediction [3], which calculates the atmospheric neutrino flux by Monte Carlo simulations.…”

Dark matter component decaying after recombination: constraints from diffuse gamma-ray and neutrino flux measurements

“…In the 100 MeV -100 TeV energy range the observed neutrino flux is dominated by the atmospheric neutrinos, that are difficult to discern from the cosmic ones. Therefore in this range we adopt experimental limits on the atmospheric neutrino flux derived by Super-Kamiokande [18] and IceCube [19] as a rough but conservative bounds for our model flux. Neutrino practically do not interact with medium during their propagation.…”