Measurement of eta meson decays into lepton-antilepton pairs

Authors :: Collaboration, CELSIUS/WASA
Berłowski, M.
Bargholtz, Chr.
Bashkanov, M.
Bogoslawsky, D.
Bondar, A.
Calén, H.
Cappellaro, F.
Clement, H.
Demirörs, L.
Ekström, C.
Fransson, K.
Gerén, L.
Gustafsson, L.
Höistad, B.
Ivanov, G.
Jacewicz, M.
Jiganov, E.
Johansson, T.
Keleta, S.
Koch, I.
Kullander, S.
Kupść, A.
Kuzmin, A.
Kuznetsov, A.
Laukhin, I. V.
Lindberg, K.
Marciniewski, P.
Meier, R.
Morosov, B.
Oelert, W.
Pauly, C.
Pettersson, H.
Petukhov, Y.
Povtorejko, A.
Ruber, R. J. M. Y.
Schönning, K.
Scobel, W.
Shafigullin, R.
Shwartz, B.
Skorodko, T.
Sopov, V.
Stepaniak, J.
Tegnér, P. -E.
Engblom, P. Thörngren
Tikhomirov, V.
Turowiecki, A.
Wagner, G. J.
Wolke, M.
Yamamoto, A.
Zabierowski, J.
Zartova, I.
Złomańczuk, J.
Publication Year :: 2007
Abstract: A search for rare lepton decays of the eta meson was performed using the WASA detector at CELSIUS. Two candidates for double Dalitz decay eta->e+e-e+e- events are reported with a background of 1.3+/-0.2 events. This allows to set an upper limit to the branching ratio of 9.7E-5 (90% CL). The branching ratio for the decay eta->e+e-gamma is determined to (7.8+/-0.5 stat+/-0.8 syst)E-3. An upper limit (90% CL) for the branching ratio for the eta->e+e- decay is 2.7E-5 and a limit for the sum of the eta->mu+mu-mu+mu- and eta->pi+pi-mu+mu- decays is 3.6E-4.<br />Comment: 9 pages, 10 Postscript figures, uses revtex4.sty, revised version after referee comments; conclusions unchanged

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