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Babusci, D.; Berlowski, M.; Bloise, C.; Bossi, F.; Branchini, P.; Cao, B.; Ceradini, F.; Ciambrone, P.; Curciarello, F.; Czerwiński, E.; D’Agostini, G.; D’Amico, R.; Danè, E.; De Leo, V.; De Lucia, E.; De Santis, A.; De Simone, P.; Di Cicco, A.; Di Domenico, A.; Diociaiuti, E.; Domenici, D.; D’Uffizi, A.; Fantini, G.; Gajos, A.; Gamrat, S.; Gauzzi, P.; Giovannella, S.; Graziani, E.; Kang, X.; Kupsc, A.; Mandaglio, G.; Martini, M.; Miscetti, S.; Moskal, P.; Passeri, A.; Perez del Rio, E.; Schioppa, M.; Selce, A.; Silarski, M.; Sirghi, F.; Solodov, E. P.; Wiślicki, W.; Wolke, M.
The journal of high energy physics, 02/2023, Volume: 2023, Issue: 2Journal Article
A bstract The ratio R = Γ( K S → πeν ) / Γ( K S → π + π − ) has been measured with a sample of 300 million K S mesons produced in ϕ → K L K S decays recorded by the KLOE experiment at the DAΦNE e + e − collider. K 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 → πeν decays are used to evaluate signal selection efficiencies. With 49647 ± 316 signal events we measure R = (1 . 0421 ± 0 . 0066 stat ± 0 . 0075 syst ) × 10 − 3 . The combination with our previous measurement gives R = (1 . 0338 ± 0 . 0054 stat ± 0 . 0064 syst ) × 10 − 3 . From this value we derive the branching fraction B ( K S → πeν ) = (7 . 153 ± 0 . 037 stat ± 0 . 044 syst ) × 10 − 4 and f + (0) |V us | = 0 . 2170 ± 0 . 009.
