  Proton decay, although unobserved so far, is a natural expectation when
attempting to explain the baryon asymmetry of the universe. $p\to K^+\bar{\nu}$
or $p\to K^+\tilde{\chi}_1^0$, with $\tilde{\chi}_1^0$ a light exotic neutral
particle, represent possible decay channels achievable in models of physics
beyond the Standard Model, such as the MSSM with trilinear R-parity-violating
terms, or the Standard Model extended by a heavy neutral lepton. Among the
decay products of these modes, the neutral fermions would typically appear as
missing energy in collider searches. The present study considers how such decay
modes could be differentiated in experimental settings, as the exotic
$\tilde{\chi}_1^0$ may further decay if it is not protected by a symmetry (such
as R-parity in the MSSM). We assess the detection prospects of the proposed
experiments DUNE, JUNO and Hyper-K in this context.
