An enhancement at the ΣK threshold (1680) MeV observed in K− p reactions at 4.2 GeV/c

Abstract An enhancement in the (Σ K ) mass spectrum at threshold is observed in K − p interactions at 4.2 GeV/ c . It appeats both in the neutral and negative charge states. Corresponding Λ K mass distributions show weak evidence for an effect close to this threshold (∼1680 MeV). Although the interpretation of the (Σ K ) enhancement by itself is ambiguous, a (Σ K )−(Λ K ) coupled channel analysis gives results compatible with its interpretation as a new Ξ ∗ .