Physics Letters B (May 2020)

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

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

Journal volume & issue
Vol. 804

Abstract

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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. Keywords: e+e− collisions, K0 meson, Semileptonic decay