2007/11/30 by WASA Collaboration, M. Berłowski, Chr. Bargholtz +57 · 45 citations
Chemistry · Mathematics · Physics and Astronomy · #Branching (polymer chemistry) #Branching fraction #Chemistry #Dark Matter and Cosmic Phenomena #Electron #Lepton #Limit (mathematics) #Mathematical analysis #Mathematics #Meson #Nuclear physics #Particle physics #Particle physics theoretical and experimental studies #Physics #Quantum Chromodynamics and Particle Interactions #hep-ex
paper · pdf · doi:10.1103/physrevd.77.032004
published in Physical review. D. Particles, fields, gravitation, and cosmology/Physical review. D. Particles and fields 77(3) (American Physical Society) · 9 pages, 10 Postscript figures, uses revtex4.sty, revised version after referee comments; conclusions unchanged
arxiv created 2008/01/16 · openalex publication_date 2008/02/26 · arxiv updated 2013/05/29 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
A search for rare lepton decays of the \ensuremathη meson was performed using the WASA detector at CELSIUS. Two candidates for double Dalitz decay \ensuremathη\ensuremath→e+e^\ensuremath-e+e^\ensuremath- events are reported with a background of 1.3\ifmmode±\else\textpm\fi0.2 events. This allows to set an upper limit to the branching ratio of 9.7\ifmmode×\else\texttimes\fi10^\ensuremath-5 (90% CL). The branching ratio for the decay \ensuremathη\ensuremath→e+e^\ensuremath-\ensuremathγ is determined to (7.8\ifmmode±\else\textpm\fi0.5stat\ifmmode±\else\textpm\fi0.8syst)\ifmmode×\else\texttimes\fi10^\ensuremath-3 in agreement with world average value. An upper limit (90% CL) for the branching ratio for the \ensuremathη\ensuremath→e+e^\ensuremath- decay is 2.7\ifmmode×\else\texttimes\fi10^\ensuremath-5 and a limit for the sum of the \ensuremathη\ensuremath→\ensuremathμ+\ensuremathμ^\ensuremath-\ensuremathμ+\ensuremathμ^\ensuremath- and \ensuremathη\ensuremath→\ensuremathπ+\ensuremathπ^\ensuremath-\ensuremathμ+\ensuremathμ^\ensuremath- decays is 3.6\ifmmode×\else\texttimes\fi10^\ensuremath-4.