Δ = 2 Neutron Decay Into Antiproton Mode
Xiao-Gang He (Physics Division, National Center for Theoretical Sciences, Hsinchu, Taiwan, Department of Physics, National Taiwan University, Taipei, Taiwan, Tsung-Dao Lee Institute, School of Physics and Astronomy, Shanghai Jiao Tong university, Shanghai, China); Xiao-Dong Ma (Department of Physics, National Taiwan University, Taipei, Taiwan, School of Nuclear Science and Technology, Lanzhou University, Lanzhou, China)
We discuss the unique baryon number violation by two units neutron decay mode , with χ being the standard model (SM) neutrino ν or antineutrino or any beyond the SM light fermion, in the framework of effective field theory. This mode is kinematically allowed but rarely discussed theoretically or searched for experimentally. We estimate the lower bound on its partial lifetime from that of the dinucleon decay per oxygen nucleus $^{16}$O set by the Super-Kamiokande experiment, with a conservative bound . We also discuss its characteristic signature for the future experimental search and astrophysical implications.