Doubly-charged scalar in four-body decays of neutral flavored mesons

We study the four-body decays of neutral flavored mesons, including K ¯ 0 , D0, B ¯ 0 , and B ¯ s 0 . These processes, which could be induced by a hypothetical doubly-charged scalar particle, do not conserve the lepton number. Assuming, as an example, that the mass of the doubly-charged particle is 1000 GeV, and using the upper bounds of the couplings, we calculate the branching ratios of different channels. For K ¯ 0 → h 1 + h 2 + e − e − , D 0 → h 1 − h 2 − e + e + , and B ¯ d , s 0 → h 1 + h 2 + e − e − , it is of the order of 10−30, 10−32–10−29, and 10−33–10−28, respectively. Based on the experimental results for the D 0 → h 1 − h 2 − l 1 + l 2 + channels, we also find the upper limit for the quantity s Δ h i j M Δ 2 .