An I = 1 enhancement at a mass of 1550 MeV in the (Λπ) and (Σπ)-systems

Abstract Evidence is presented for an I = 1 enhancement observed in the reactions K − p→ Λ ( Σ )K 0 1 K ± π ∓ at 4.2 GeV c inciden momentum. The mass and width of the proposed new Y ∗ are, respectively, (1553 ± 7) MeV) and (80 ± 30) MeV. A decay branching ratio Σπ (Σπ + Λπ) = (35 ± 12)% is also obtained.