Nuclear and nucleon transitions of the H dibaryon

We consider 3 types of processes pertinent to the phenomenology of an H dibaryon: conversion of two Λ's in a doubly strange hypernucleus to an H, decay of the H to two baryons, and-if the H is light enough-conversion of two nucleons in a nucleus to an H. We compute the spatial wave function overlap using the Isgur-Karl, Miller-Spencer and Bethe-Goldstone wave functions, and treat the weak interactions phenomenologically. The observation of Λ decays from doubly strange hypernuclei puts a constraint on the H wave function which is plausibly satisfied. Imposing this constraint, we obtain model-independent lower limits on the H lifetime; if m_H<m _N+m_Λ, the H lifetime can be of the order of or longer than the age of the Universe. We discuss limits on a long-lived or stable H, and point out how experiments can improve the constraints.