Search for solar electron anti-neutrinos due to spin-flavor precession in the Sun with Super-Kamiokande-IV

Abe, K.; Bronner, C.; Hayato, Y.; Ikeda, M.; Imaizumi, S.; Ito, H.; Kameda, J.; Kataoka, Y.; Miura, M.; Moriyama, S.; Nagao, Y.; Nakahata, M.; Nakajima, Y.; Nakayama, S.; Okada, T.; Okamoto, K.; Orii, A.; Pronost, G.; Sekiya, H.; Shiozawa, M.; Sonoda, Y.; Suzuki, Y.; Takeda, A.; Takemoto, Y.; Takenaka, A.; Tanaka, H.; Yano, T.; Akutsu, R.; Han, S.; Kajita, T.; Okumura, K.; Tashiro, T.; Wang, R.; Xia, J.; Bravo-Berguno, D.; Labarga, L.; Marti, L.; Zaldivar, B.; Blaszczyk, F. D. M.; Kearns, E.; Raaf, J. L.; Stone, J. L.; Wan, L.; Wester, T.; Pointon, B. W.; Bian, J.; Griskevich, N. J.; Kropp, W. R.; Locke, S.; Mine, S.; Smy, M. B.; Sobel, H. W.; Takhistov, V.; Weatherly, P.; Hill, J.; Kim, J. Y.; Lim, I. T.; Park, R. G.; Bodur, B.; Scholberg, K.; Walter, C. W.; Bernard, L.; Coffani, A.; Drapier, O.; Hedri, S. E.; Giampaolo, A.; Gonin, M.; Mueller, T. A.; Paganini, P.; Quilain, B.; Ishizuka, T.; Nakamura, T.; Jang, J. S.; Learned, J. G.; Anthony, L. H. V.; Sztuc, A. A.; Uchida, Y.; Berardi, V.; Catanesi, M. G.; Radicioni, E.; Calabria, N. F.; Machado, L. N.; De Rosa, G.; Collazuol, G.; Iacob, F.; Lamoureux, M.; Ospina, N.; Ludovici, L.; Nishimura, Y.; Cao, S.; Friend, M.; Hasegawa, T.; Ishida, T.; Jakkapu, M.; Kobayashi, T.; Matsubara, T.; Nakadaira, T.; Nakamura, K.; Oyama, Y.; Sakashita, K.; Sekiguchi, T.; Tsukamoto, T.; Nakano, Y.; Shiozawa, T.; Suzuki, A. T.; Takeuchi, Y.; Yamamoto, S.; Ali, A.; Ashida, Y.; Feng, J.; Hirota, S.; Ichikawa, A. K.; Kikawa, T.; Mori, M.; Nakaya, T.; Wendell, R. A.; Yasutome, Y.; Fernandez, P.; Mccauley, N.; Mehta, P.; Pritchard, A.; Tsui, K. M.; Fukuda, Y.; Itow, Y.; Menjo, H.; Niwa, T.; Sato, K.; Tsukada, M.; Mijakowski, P.; Jung, C. K.; Vilela, C.; Wilking, M. J.; Yanagisawa, C.; Harada, M.; Hagiwara, K.; Horai, T.; Ishino, H.; Ito, S.; Koshio, Y.; Ma, W.; Piplani, N.; Sakai, S.; Kuno, Y.; Barr, G.; Barrow, D.; Cook, L.; Goldsack, A.; Samani, S.; Simpson, C.; Wark, D.; Nova, F.; Boschi, T.; Di Lodovico, F.; Taani, M.; Migenda, J.; Sedgwick, S. M.; Zsoldos, S.; Yang, J. Y.; Jenkins, S. J.; Malek, M.; Mcelwee, J. M.; Stone, O.; Thiesse, M. D.; Thompson, L. F.; Okazawa, H.; Kim, S. B.; Yu, I.; Nishijima, K.; Koshiba, M.; Iwamoto, K.; Ogawa, N.; Yokoyama, M.; Martens, K.; Vagins, M. R.; Izumiyama, S.; Kuze, M.; Tanaka, M.; Yoshida, T.; Inomoto, M.; Ishitsuka, M.; Matsumoto, R.; Ohta, K.; Shinoki, M.; Martin, J. F.; Tanaka, H. A.; Towstego, T.; Hartz, M.; Konaka, A.; de Perio, P.; Prouse, N. W.; Chen, S.; B. D., Xu; Richards, B.; Jamieson, B.; Walker, J.; Minamino, A.; Pintaudi, G.; Sasaki, R.; Posiadala-Zezula, M.

doi:10.1016/j.astropartphys.2022.102702

Due to a very low production rate of electron anti-neutrinos (ν̄e) via nuclear fusion in the Sun, a flux of solar ν̄e is unexpected. An appearance of ν̄e 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 (νe→ν̄e) when neutrino has a finite magnetic moment. In this work, we have searched for solar ν̄e in the Super-Kamiokande experiment, using neutron tagging to identify their inverse beta decay signature. We identified 78 ν̄e 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⋅year exposure). The energy spectrum has been consistent with background predictions and we thus derived a 90% confidence level upper limit of 4.7×10−4 on the νe→ν̄e conversion probability in the Sun. We used this result to evaluate the sensitivity of future experiments, notably the Super-Kamiokande Gadolinium (SK-Gd) upgrade.