Known and exotic light hypernuclei studied with the 6Li+12C reaction at 2 A GeV

Abstract

Light hypernuclei have been studied by using induced reactions of 6Li projectiles bombarded on the natural carbon target by means of the invariant mass method, and 3ΛH and 4ΛH hypernuclei as well as Λ-hyperons are produced and identified. Significance values of 3ΛH, 4ΛH and Λ are respectively 4.7σ, 4.9σ and 6.7σ. By analyzing decay vertices of 3ΛH, 4ΛH and Λ by means of unbinned maximum likelihood fitting their lifetime values have been deduced to be 183+42−32 ps, 140+48-33 ps and 262+56-43 ps, respectively. In addition, signals appeared for the d+π- and t+π- final states in the analyses on invariant mass and lifetime. Those signals have suggested a possible bound state of two neutrons with Λ, 3Λn. It has also been revealed for the first time that the lifetime of 3ΛH is significantly shorter than that of Λ, which is consistent to the statistical analyses including all the lifetime data reported in the past. However, there is no theoretical model to explain the short lifetime of 3ΛH as well as the existence of the 3Λn bound state. These should be further experimentally and theoretically studied.