Search for proton decay via <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>p</mml:mi><mml:mo stretchy="false">→</mml:mo><mml:msup><mml:mi>e</mml:mi><mml:mo>+</mml:mo></mml:msup><mml:msup><mml:mi>π</mml:mi><mml:mn>0</mml:mn></mml:msup></mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>p</mml:mi><mml:mo stretchy="false">→</mml:mo><mml:msup><mml:mi>μ</mml:mi><mml:mo>+</mml:mo></mml:msup><mml:msup><mml:mi>π</mml:mi><mml:mn>0</mml:mn></mml:msup></mml:math> with an enlarged fiducial volume in Super-Kamiokande I-IV
A. Takenaka, K. Abe, C. Bronner, Y. Hayato, M. Ikeda, S. Imaizumi, Hiroshi Itô, J. Kameda, Y. Kataoka, Y. Kato, Y. Kishimoto, Ll. Marti, M. Miura, S. Moriyama, T. Mochizuki, Y. Nagao, M. Nakahata, Y. Nakajima, S. Nakayama, T. Okada, Ken‐ichi Okamoto, A. Orii, G. Pronost, H. Sekiya, M. Shiozawa, Y. Sonoda, Y. Suzuki, A. Takeda, Y. Takemoto, Hiroyuki Tanaka, T. Yano, R. Akutsu, S. Han, T. Kajita, K. Okumura, T. Tashiro, R. Wang, J. Xia, D. Bravo, L. Labarga, P. Fernández, B. Zaldivar, F. d. M. Blaszczyk, E. Kearns, J. L. Raaf, J. L. Stone, L. Wan, T. Wester, B. W. Pointon, J. Bian, N. J. Griskevich, W. R. Kropp, S. Locke, S. Mine, M. Smy, H. W. Sobel, Volodymyr Takhistov, P. Weatherly, K. S. Ganezer, J. Hill, J. Y. Kim, I. T. Lim, R. G. Park, B. Bodur, K. Scholberg, C. W. Walter, A. Coffani, O. Drapier, S. El Hedri, A. Giampaolo, M. Gonin, Th. A. Mueller, P. Paganini, B. Quilain, T. Ishizuka, T. Nakamura, J. S. Jang, J. G. Learned, S. Matsuno, L. H. V. Anthony, R. P. Litchfield, A. A. Sztuc, Y. Uchida, V. Berardi, J. Chakrani, E. Radicioni, N. F. Calabria, L. N. Machado, G. De Rosa, G. Collazuol, F. Iacob, M. Lamoureux, N. Ospina, L. Ludovici, Y. Nishimura, S. Cao, M. Friend, T. Hasegawa, T. Ishida, M. Jakkapu
Abstract
We have searched for proton decay via $p\ensuremath{\rightarrow}{e}^{+}{\ensuremath{\pi}}^{0}$ and $p\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\pi}}^{0}$ modes with the enlarged fiducial volume data of Super-Kamiokande from April 1996 to May 2018, which corresponds to $450\text{ }\text{ }\mathrm{kton}\ifmmode\cdot\else\textperiodcentered\fi{}\mathrm{years}$ exposure. We have accumulated about 25% more livetime and enlarged the fiducial volume of the Super-Kamiokande detector from 22.5 kton to 27.2 kton for this analysis, so that $144\text{ }\text{ }\mathrm{kton}\ifmmode\cdot\else\textperiodcentered\fi{}\mathrm{years}$ of data, including $78\text{ }\text{ }\mathrm{kton}\ifmmode\cdot\else\textperiodcentered\fi{}\mathrm{years}$ of additional fiducial volume data, has been newly analyzed. No candidates have been found for $p\ensuremath{\rightarrow}{e}^{+}{\ensuremath{\pi}}^{0}$ and one candidate remains for $p\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\pi}}^{0}$ in the conventional 22.5 kton fiducial volume and it is consistent with the atmospheric neutrino background prediction. We set lower limits on the partial lifetime for each of these modes: $\ensuremath{\tau}/B(p\ensuremath{\rightarrow}{e}^{+}{\ensuremath{\pi}}^{0})>2.4\ifmmode\times\else\texttimes\fi{}{10}^{34}\text{ }\text{ }\mathrm{years}$ and $\ensuremath{\tau}/B(p\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\pi}}^{0})>1.6\ifmmode\times\else\texttimes\fi{}{10}^{34}\text{ }\text{ }\mathrm{years}$ at 90% confidence level.