Using the Double Chooz detector, designed to measure the neutrino mixing angle θ13, the products of μ- capture on C12,C13,N14, and O16 have been measured. Over a period of 489.5 days, 2.3×106 stopping cosmic μ- have been collected, of which 1.8×105 captured on carbon, nitrogen, or oxygen nuclei in the inner detector scintillator or acrylic vessels. The resulting isotopes were tagged using prompt neutron emission (when applicable), the subsequent β decays, and, in some cases, β-delayed neutrons. The most precise measurement of the rate of C12(μ-,ν)B12 to date is reported: 6.57-0.21+0.11×103s-1, or (17.35-0.59+0.35)% of nuclear captures. By tagging excited states emitting γs, the ground state transition rate to B12 has been determined to be 5.68-0.23+0.14×103s-1. The heretofore unobserved reactions C12(μ-,να)Li8,C13(μ-,νnα)Li8, and C13(μ-,νn)B12 are measured. Further, a population of βn decays following stopping muons is identified with 5.5σ significance. Statistics limit our ability to identify these decays definitively. Assuming negligible production of He8, the reaction C13(μ-,να)Li9 is found to be present at the 2.7σ level. Limits are set on a variety of other processes.
Bibliographical noteFunding Information:
We acknowledge the support of the CEA, CNRS/IN2P3, the computer center CCIN2P3, and LabEx UnivEarthS in France (ANR-11-IDEX-0005-02); the Ministry of Education, Culture, Sports, Science and Technology of Japan (MEXT) and the Japan Society for the Promotion of Science (JSPS); the Department of Energy and the National Science Foundation of the United States; U.S. Department of Energy Award No. DE-NA0000979 through the Nuclear Science and Security Consortium; the Ministerio de Economia y Competitividad (MINECO) of Spain; the Max Planck Gesellschaft, and the Deutsche Forschungsgemeinschaft DFG, the Transregional Collaborative Research Center TR27, the excellence cluster Origin and Structure of the Universe, and the Maier-Leibnitz-Laboratorium Garching in Germany; the Russian Academy of Science, the Kurchatov Institute and RFBR (the Russian Foundation for Basic Research); the Brazilian Ministry of Science, Technology and Innovation (MCTI), the Financiadora de Estudos e Projetos (FINEP), the Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq), the Sao Paulo Research Foundation (FAPESP), and the Brazilian Network for High Energy Physics (RENAFAE) in Brazil.