Double beta decay of Σ- hyperons

We compute the strangeness-conserving double beta decay of Sigma(-) hyperons, which is the only hadronic system that can undergo such decays. We consider both, the lepton number conserving Sigma(-) --> Sigma(+)e(-)e(-)(nu) over bar(nu) over bar (betabetaSigma2(nu)) and the lepton number violating E- -->. Sigma(+)e(-)e(-) (betabeta(Sigma0nu)) modes. The branching ratios of these betabeta decays are suppressed at the level of 10(-30) considering a light neutrino scenario in the case of the betabeta(Sigma0nu) channel. The dynamical origin of such low rates and their possible enhancements are briefly discussed. Given its simplicity those decays can be used also for the purposes of illustrating the main features of double beta decays. (C) 2003 Published by Elsevier B.V.