Direct Observation of Sequential Weak Decay of a Double Hypernucleus

Abstract

We have studied stars in nuclear emulsion due to the capture at rest of the Ξ- hyperons produced in the (<it>K</it>-, <it>K</it>+) reaction. The sequential weak decay of a double hypernucleus (nucleus with <it>S</it> = -2) has been directly observed. The double hypernucleus is assigned as either 10<inf>ΛΛ</inf>Be or 13<inf>ΛΛ</inf>B. This assignment excludes the existence of the <it>H</it> dibaryon lighter than 2203.7 ±0.7 MeV/c2.