Measurement of the branching fraction for the decay KS → πμν with the KLOE detector

01 Pubblicazione su rivista
Babusci D., Berlowski M., Bloise C., Bossi F., Branchini P., Budano A., Cao B., Ceradini F., Ciambrone P., Curciarello F., Czerwinski E., D'Agostini G., Dane E., De Leo V., De Lucia E., De Santis A., De Simone P., Di Cicco A., Di Domenico A., Domenici D., D'Uffizi A., Fantini A., Fermani P., Fiore S., Gajos A., Gauzzi P., Giovannella S., Graziani E., Ivanov V. L., Johansson T., Kang X., Kisielewska-Kaminska D., Kozyrev E. A., Krzemien W., Kupsc A., Lukin P. A., Mandaglio G., Martini M., Messi R., Miscetti S., Moricciani D., Moskal P., Parzych S., Passeri A., Patera V., Perez del Rio E., Santangelo P., Schioppa M., Selce A., Silarski M., Sirghi F., Solodov E. P., Tortora L., Venanzoni G., Wislicki W., Wolke M.
ISSN: 0370-2693

Based on a sample of 300 million KS mesons produced in ϕ→KLKS decays recorded by the KLOE experiment at the DAΦNE e+e− collider we have measured the branching fraction for the decay KS→πμν. The KS mesons are identified by the interaction of KL mesons in the detector. The KS→πμν decays are selected by a boosted decision tree built with kinematic variables and by a time-of-flight measurement. Signal efficiencies are evaluated with data control samples of KL→πμν decays. A fit to the reconstructed muon mass distribution finds 7223±180 signal events. Normalising to the KS→π+π− decay events the result for the branching fraction is B(KS→πμν)=(4.56±0.11stat±0.17syst)×10−4. It is the first measurement of this decay mode and the result allows an independent determination of |Vus| and a test of the lepton-flavour universality.

© Università degli Studi di Roma "La Sapienza" - Piazzale Aldo Moro 5, 00185 Roma