Improved upper limits on baryon-number violating dinucleon decays to dileptons

We consider effects of n−n¯ oscillations and resultant matter instability due to dinucleon decays. We point out that existing upper bounds on the rates for the dinucleon decays nn→2π⁰, nn→π⁺π⁻, and np→π⁺π⁰ imply upper bounds on the rates for dinucleon decays to dileptons nn→e⁺e⁻, nn→μ⁺μ⁻, nn→ν_ℓν¯_ℓ, and np→ℓ⁺ν_ℓ, where ℓ=e,μ,τ. We present estimates for these upper bounds. Our bounds are substantially stronger than corresponding limits from direct searches.