An upper limit for the branching ratio of the decay Ks → e+e−

A Angelopoulos,E Gabathuler,W Fetscher,A Benelli,A Schopper,P Carlson,C Touramanis,E Machado,A Haselden,F Leimgruber,L Tauscher,M Fidecaro,O Wigger,A Ealet,P Pavlopoulos,G Marel,G Polivka,E Hubert,R Le Gac,T Ruf,G Backenstoss,R Kreuger,J Pinto Da Cunha,O Behnke,R Rickenbach,D Zimmerman,A Go,A Apostolakis,D Garreta,A Liolios,T Schietinger,L Sakeliou,L Faravel,R.W Hollander,P Sanders,C Eleftheriadis,P Bloch,R Gamet,G Chardin,F Blanc,C Thibault,B Pagels,E Cawley,M Chertok ,J Gerberh ,R Ferreira‐Marques ,B L Roberts ,Ch Yèche ,M Déjardin ,A Soares ,I Mandić ,S Charalambous ,N Manthos ,T Nakada ,D Francis ,E Aslanides ,C We Van Eijk ,Mats Danielsson ,M W Wolter ,F Henry Couannier ,J Derré ,A Filipčǐc ,Eef Van Beveren ,J Miller ,I Evangelou ,V Bertín ,A Policarpo ,F Montanet ,Ann Marie Cody ,D Zavrtanik ,P Kokkas ,P.r Kettle ,F A Triantis ,L.a Schaller ,S Vlachos ,J Carvalho ,A Müller ,F Touchard ,I Papadopoulos ,Peter M Weber ,J R Fry ,K Jon And ,M Mikuž ,M Schaefer ,P Hayman

doi:10.1016/s0370-2693(97)01187-8

Abstract

A search for the decay KS → e+e− was performed within the framework of the CPLEAR experiment. Full event reconstruction together with e/π separation allowed powerful background rejection and high signal acceptance. The analysis of the complete set of data yields the result: BR(KS → e+e−) < 1.4 × 10−7 (90% CL), an improvement on the current experimental limit by a factor of 20.

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