This paper reports results from a search for nucleon decay through invisible modes, where no visible energy is directly deposited during the decay itself, during the initial water phase of SNO+. However, such decays within the oxygen nucleus would produce an excited daughter that would subsequently deexcite, often emitting detectable gamma rays. A search for such gamma rays yields limits of 2.5×1029 y at 90% Bayesian credibility level (with a prior uniform in rate) for the partial lifetime of the neutron, and 3.6×1029 y for the partial lifetime of the proton, the latter a 70% improvement on the previous limit from SNO. We also present partial lifetime limits for invisible dinucleon modes of 1.3×1028 y for nn, 2.6×1028 y for pn and 4.7×1028 y for pp, an improvement over existing limits by close to 3 orders of magnitude for the latter two.
Bibliographical noteFunding Information:
Capital construction funds for the experiment were provided by the Canada Foundation for Innovation (CFI) and matching partners. This research was supported by the following: Canada: Natural Sciences and Engineering Research Council, the Canadian Institute for Advanced Research (CIFAR), Queen’s University at Kingston, Ontario Ministry of Research, Innovation and Science, Alberta Science and Research Investments Program, National Research Council, Federal Economic Development Initiative for Northern Ontario, Northern Ontario Heritage Fund Corporation, Ontario Early Researcher Awards; U.S.: Department of Energy Office of Nuclear Physics, National Science Foundation, the University of California, Berkeley, Department of Energy National Nuclear Security Administration through the Nuclear Science and Security Consortium; UK: Science and Technology Facilities Council (STFC), the European Union’s Seventh Framework Programme under the European Research Council (ERC) grant agreement, the Marie Curie grant agreement; Portugal: Fundação para a Ciência e a Tecnologia (FCT-Portugal); Germany: the Deutsche Forschungsgemeinschaft; Mexico: DGAPA-UNAM and Consejo Nacional de Ciencia y Tecnología. We thank the technical staff for their strong contributions. We would like to thank SNOLAB and its staff for support through underground space, logistical and technical services. SNOLAB operations are supported by CFI and the Province of Ontario Ministry of Research and Innovation, with underground access provided by Vale at the Creighton mine site. This research was enabled in part by support provided by WestGRID ( www.westgrid.ca ) and ComputeCanada ( www.computecanada.ca ), in particular computer systems and support from the University of Alberta ( www.ualberta.ca ) and from Simon Fraser University ( www.sfu.ca ), and by the GridPP Collaboration, in particular computer systems and support from Rutherford Appleton Laboratory . Additional high-performance computing was provided through the “Illume” cluster funded by CFI and Alberta Economic Development and Trade (EDT) and operated by ComputeCanada and the Savio computational cluster resource provided by the Berkeley Research Computing program at the University of California, Berkeley (supported by the UC Berkeley Chancellor, Vice Chancellor for Research, and Chief Information Officer). Additional long-term storage was provided by the Fermilab Scientific Computing Division. Fermilab is managed by Fermi Research Alliance, LLC (FRA) under Contract with the U.S. Department of Energy, Office of Science, Office of High Energy Physics.