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

(Super-Kamiokande Collaboration)

Research output: Contribution to journalArticle

26 Citations (Scopus)

Abstract

A comprehensive study of the atmospheric neutrino flux in the energy region from sub-GeV up to several TeV using the Super-Kamiokande (SK) 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 8.0σ and 6.0σ significance, respectively, and an indication that the asymmetry dipole angle changes depending on the zenith angle was seen at the 2.2σ 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 1.1σ level, using SK-I-SK-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 2.4σ 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.

Original languageEnglish
Article number052001
JournalPhysical Review D
Volume94
Issue number5
DOIs
Publication statusPublished - Sep 2 2016

Fingerprint

magnetic effects
energy spectra
neutrinos
modulation
zenith
asymmetry
Forbush decreases
solar activity
energy
indication
topology
dipoles
deviation
detectors
predictions
water

ASJC Scopus subject areas

  • Physics and Astronomy (miscellaneous)

Cite this

Measurements of the atmospheric neutrino flux by Super-Kamiokande : Energy spectra, geomagnetic effects, and solar modulation. / (Super-Kamiokande Collaboration).

In: Physical Review D, Vol. 94, No. 5, 052001, 02.09.2016.

Research output: Contribution to journalArticle

@article{2acc75f4e5ad4f5198bac1db306d5331,
title = "Measurements of the atmospheric neutrino flux by Super-Kamiokande: Energy spectra, geomagnetic effects, and solar modulation",
abstract = "A comprehensive study of the atmospheric neutrino flux in the energy region from sub-GeV up to several TeV using the Super-Kamiokande (SK) 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 8.0σ and 6.0σ significance, respectively, and an indication that the asymmetry dipole angle changes depending on the zenith angle was seen at the 2.2σ 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 1.1σ level, using SK-I-SK-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 2.4σ 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.",
author = "{(Super-Kamiokande Collaboration)} and E. Richard and K. Okumura and K. Abe and Y. Haga and Y. Hayato and M. Ikeda and K. Iyogi and J. Kameda and Y. Kishimoto and M. Miura and S. Moriyama and M. Nakahata and T. Nakajima and Y. Nakano and S. Nakayama and A. Orii and H. Sekiya and M. Shiozawa and A. Takeda and H. Tanaka and T. Tomura and Wendell, {R. A.} and R. Akutsu and T. Irvine and T. Kajita and K. Kaneyuki and Y. Nishimura and L. Labarga and P. Fernandez and J. Gustafson and C. Kachulis and E. Kearns and Raaf, {J. L.} and Stone, {J. L.} and Sulak, {L. R.} and S. Berkman and Nantais, {C. M.} and Tanaka, {H. A.} and S. Tobayama and M. Goldhaber and Kropp, {W. R.} and S. Mine and P. Weatherly and Smy, {M. B.} and Sobel, {H. W.} and V. Takhistov and Ganezer, {K. S.} and Hirokazu Ishino and Yusuke Koshio and Makoto Sakuda",
year = "2016",
month = "9",
day = "2",
doi = "10.1103/PhysRevD.94.052001",
language = "English",
volume = "94",
journal = "Physical Review D",
issn = "2470-0010",
publisher = "American Physical Society",
number = "5",

}

TY - JOUR

T1 - Measurements of the atmospheric neutrino flux by Super-Kamiokande

T2 - Energy spectra, geomagnetic effects, and solar modulation

AU - (Super-Kamiokande Collaboration)

AU - Richard, E.

AU - Okumura, K.

AU - Abe, K.

AU - Haga, Y.

AU - Hayato, Y.

AU - Ikeda, M.

AU - Iyogi, K.

AU - Kameda, J.

AU - Kishimoto, Y.

AU - Miura, M.

AU - Moriyama, S.

AU - Nakahata, M.

AU - Nakajima, T.

AU - Nakano, Y.

AU - Nakayama, S.

AU - Orii, A.

AU - Sekiya, H.

AU - Shiozawa, M.

AU - Takeda, A.

AU - Tanaka, H.

AU - Tomura, T.

AU - Wendell, R. A.

AU - Akutsu, R.

AU - Irvine, T.

AU - Kajita, T.

AU - Kaneyuki, K.

AU - Nishimura, Y.

AU - Labarga, L.

AU - Fernandez, P.

AU - Gustafson, J.

AU - Kachulis, C.

AU - Kearns, E.

AU - Raaf, J. L.

AU - Stone, J. L.

AU - Sulak, L. R.

AU - Berkman, S.

AU - Nantais, C. M.

AU - Tanaka, H. A.

AU - Tobayama, S.

AU - Goldhaber, M.

AU - Kropp, W. R.

AU - Mine, S.

AU - Weatherly, P.

AU - Smy, M. B.

AU - Sobel, H. W.

AU - Takhistov, V.

AU - Ganezer, K. S.

AU - Ishino, Hirokazu

AU - Koshio, Yusuke

AU - Sakuda, Makoto

PY - 2016/9/2

Y1 - 2016/9/2

N2 - A comprehensive study of the atmospheric neutrino flux in the energy region from sub-GeV up to several TeV using the Super-Kamiokande (SK) 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 8.0σ and 6.0σ significance, respectively, and an indication that the asymmetry dipole angle changes depending on the zenith angle was seen at the 2.2σ 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 1.1σ level, using SK-I-SK-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 2.4σ 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.

AB - A comprehensive study of the atmospheric neutrino flux in the energy region from sub-GeV up to several TeV using the Super-Kamiokande (SK) 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 8.0σ and 6.0σ significance, respectively, and an indication that the asymmetry dipole angle changes depending on the zenith angle was seen at the 2.2σ 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 1.1σ level, using SK-I-SK-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 2.4σ 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.

UR - http://www.scopus.com/inward/record.url?scp=84990859007&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84990859007&partnerID=8YFLogxK

U2 - 10.1103/PhysRevD.94.052001

DO - 10.1103/PhysRevD.94.052001

M3 - Article

AN - SCOPUS:84990859007

VL - 94

JO - Physical Review D

JF - Physical Review D

SN - 2470-0010

IS - 5

M1 - 052001

ER -