Finding nucleon decay through ghostly delayed signals

Nucleon decay searches hunt for baryon number violation, but standard methods only catch immediate, prompt decays. This work proposes "echo" signatures: the proton decays into a long-lived particle that travels meters before decaying again, creating two spatially separated but correlated detection events. Water Cherenkov detectors like Super-Kamiokande and the planned Hyper-Kamiokande could catch 80% of such events, opening a new window on physics beyond the Standard Model.