Determination of the branching ratiosΓ(KL→3π0)/Γ(KL→π+-0) andΓ(KL→3π0)/Γ(KL→πev)

Improved branching ratios were measured for theKL→3π0 decay in a neutral beam at the CERN SPS with the NA31 detector: $$\Gamma ({\rm K}_L \to 3\pi ^0 )/\Gamma ({\rm K}_L \to \pi ^ + \pi ^ - \pi ^0 ) = 1.611 \pm 0.037$$ and $$\Gamma ({\rm K}_L \to 3\pi ^0 )/\Gamma ({\rm K}_L \to \pi ev) = 0.545 \pm 0.010.$$ From the first number an upper limit for ΔI=5/2 and ΔI=7/2 transitions in neutral kaon decay is derived. Using older results for the Ke3/Kμ3 fraction, the 3π0 branching ratio is found to beΓ(K L →3π0)/Γ tot =(0.211±0.003), about a factor three more precise than from previous experiments.