Has the neutral double hypernucleus been observed?

Abstract

The BNL-AGS E906 experiment was the first fully electronic experiment to produce and study double hypernuclei with large statistics. Unfortunately, the interpretation of the measured π−−π− momentum correlation is still blurry because the hypothesized production of pairs remains questionable. We show, that neither a scenario where the hypernuclei are produced after the capture of a stopped Ξ− by a 9Be nucleus nor interactions of energetic Ξ− with 9 Be nuclei in the target material can produce a sufficient amount of such pairs. We have therefore explored the conjecture that decays of themay be responsible for the observed structure. Indeed, the inclusion of with a two-body π− branching ratio of 50% in the statistical multifragmentation model allows to describe the E906 data remarkably well.