The ratio R R = Γ(K S S → πeν)/Γ(K S S → π + + π − − ) has been measured with a sample of 300 million K S S mesons produced in ϕ → K L L K S S decays recorded by the KLOE experiment at the DAΦNE e + + e − − collider. K S S → πeν events are selected by a boosted decision tree built with kinematic variables and time-of-flight measurements. Data control samples of K L L → πeν decays are used to evaluate signal selection efficiencies. With 49647±316 signal events we measure R R = (1.0421 ± 0.0066 s t a t stat ± 0.0075 s y s t syst ) × 10 − 3 −3 . The combination with our previous measurement gives R R = (1.0338 ± 0.0054 s t a t stat ± 0.0064 s y s t syst ) × 10 − 3 −3 . From this value we derive the branching fraction B B(K S S → πeν) = (7.153 ± 0.037 s t a t stat ± 0.044 s y s t syst ) × 10 − 4 −4 and f + + (0)|V u s us | = 0.2170 ± 0.009.
Measurement of the KS→ πeν branching fraction with the KLOE experiment
Martini M;
2023-01-01
Abstract
The ratio R R = Γ(K S S → πeν)/Γ(K S S → π + + π − − ) has been measured with a sample of 300 million K S S mesons produced in ϕ → K L L K S S decays recorded by the KLOE experiment at the DAΦNE e + + e − − collider. K S S → πeν events are selected by a boosted decision tree built with kinematic variables and time-of-flight measurements. Data control samples of K L L → πeν decays are used to evaluate signal selection efficiencies. With 49647±316 signal events we measure R R = (1.0421 ± 0.0066 s t a t stat ± 0.0075 s y s t syst ) × 10 − 3 −3 . The combination with our previous measurement gives R R = (1.0338 ± 0.0054 s t a t stat ± 0.0064 s y s t syst ) × 10 − 3 −3 . From this value we derive the branching fraction B B(K S S → πeν) = (7.153 ± 0.037 s t a t stat ± 0.044 s y s t syst ) × 10 − 4 −4 and f + + (0)|V u s us | = 0.2170 ± 0.009.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
