1. Measurement of eta meson decays into lepton-antilepton pairs
- Author
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WASA Collaboration, Ber��owski, M., Bargholtz, Chr., Bashkanov, M., Bogoslawsky, D., Bondar, A., Cal��n, H., Cappellaro, F., Clement, H., Demir��rs, L., Ekstr��m, C., Fransson, K., Ger��n, L., Gustafsson, L., H��istad, B., Ivanov, G., Jacewicz, M., Jiganov, E., Johansson, T., Keleta, S., Koch, I., Kullander, S., Kup����, 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., Sch��nning, K., Scobel, W., Shafigullin, R., Shwartz, B., Skorodko, T., Sopov, V., Stepaniak, J., Tegn��r, P. -E., Engblom, P. Th��rngren, Tikhomirov, V., Turowiecki, A., Wagner, G. J., Wolke, M., Yamamoto, A., Zabierowski, J., Zartova, I., and Z��oma��czuk, J.
- Subjects
Nuclear and High Energy Physics ,Particle physics ,Meson ,Nuclear Theory ,decay modes [eta] ,Dalitz plot ,FOS: Physical sciences ,Electron ,Particle identification ,exclusive reaction [p deuteron] ,High Energy Physics - Experiment ,Nuclear physics ,Particle decay ,High Energy Physics - Experiment (hep-ex) ,pair production [lepton] ,+helium-3+eta%22">p deuteron --> helium-3 eta ,+2lepton%2B+2lepton%22">eta --> 2lepton+ 2lepton ,ddc:530 ,+2positron+2electron%22">eta --> 2positron 2electron ,semileptonic decay [eta] ,Nuclear Experiment ,0.893 GeV ,+pi%2B+pi-+muon%2B+muon%22">eta --> pi+ pi- muon+ muon ,branching ratio [eta] ,Physics ,hadroproduction [eta] ,experimental results [magnetic spectrometer] ,leptonic decay [eta] ,Branching fraction ,High Energy Physics::Phenomenology ,Eta meson ,+positron+electron%22">eta --> positron electron ,Uppsala CELSIUS Stor ,+2muon%2B+2muon%22">eta --> 2muon+ 2muon ,High Energy Physics::Experiment ,+positron+electron+photon%22">eta --> positron electron photon ,upper limit ,Lepton ,experimental results - 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., 9 pages, 10 Postscript figures, uses revtex4.sty, revised version after referee comments; conclusions unchanged
- Published
- 2007
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