K⁰ _S production in τ decays

From a sample of about 160k Z → τ⁺τ^- candidates collected with the ALEPH detector at LEP between 1991 and 1995, τ lepton decays involving K⁰ _S → π⁺π^- are studied. The K⁰ _SK⁰ _L associated production in τ decays is also investigated. The branching ratios are measured for the inclusive decay B(τ^-→K⁰ _SX^-ν _τ) = (9.70±0.58±0.62) × 10^-3, where X^- can be anything, and for the exclusive decays B(τ^-→K̄⁰π^-ν _τ) = (8.55±1.17±0.66) × 10^-3, B(τ^-→K̄⁰π^-π ⁰ν_τ) = (2.94±0.73±0.37) × 10^-3, B(τ^-→K̄⁰K^-ν_τ) = (1.58±0.42±0.17) × 10^-3, B(τ^-→K̄⁰K^-π ⁰ν_τ) = (1.52±0.76±0.21) × 10^-3. The decay τ^-→K⁰ _SK⁰ _Lπ^-ν_τ is studied for the first time, giving a branching ratio B(τ^-→K⁰ _SK⁰ _Lπ^-ν_τ) = (1.01±0.23±0.13) × 10^-3. The channels τ^- → K⁰ _SK⁰ _Sπ^-ν _τ , τ^- → K⁰ _SK⁰ _Sπ^-π ⁰ν_τ , τ^- → K⁰ _SK⁰ _Lπ^-π ⁰ν_τ , τ^- → K̄⁰π^-π⁰π⁰ν _τ, τ^-→K⁰K^-π⁰π ⁰ν_τ and τ^-→K⁰h⁺h^-h ^-ν_τ are also investigated. In addition, mass spectra in the K⁰ _Sh^- and K⁰ _Sh^-π⁰ final states are analysed to provide information on the intermediate states produced in the decays.