A new upper limit for the branching ratio for the decay η → π0e+e−

Jane, M.R.; Grannis, P. D.; Jones, B. D.; Lipman, N.H.; Owen, D.; Peterson, V.Z.; Toner, W.T.; Bellamy, E.H.; Green, M.G.; Kirkby, J.; Solomonides, C.M.; Strong, J. A.; Thomas, D.H.

doi:10.1016/0370-2693(75)90167-7

Cited by 10 publications

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“…The main SM contribution to this process (shown in Figure 2) comes from the C-conserving exchange of two intermediate photons (η and, moreover, has to have a vanishing transition form factor in the on-shell limit, since -as stated above -the direct η π 0 γ vertex is forbidden by angular momentum conservation [24]. At present, the empirical upper limit for the BRÔη π 0 e e ¡ Õ is equal to 4.5 ¤ 10 ¡5 90% CL, which comes from an 1975 experiment [30]. The data used for obtaining this limit were analyzed under assumption of a constant decay matrix element and a cut M Ôe e ¡ Õ 140 MeV was applied.…”

Section: Tests Of C Symmetrymentioning

confidence: 94%

Tests of the fundamental symmetries in eta meson decays

Kupsc,

Wirzba

2011

Preprint

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Patterns of chiral symmetry violation and tests of the conservation of the fundamental C, P and CP symmetries are key physics issues in studies of the π 0 , η and η ½ meson decays. These tests include searches for rare or forbidden decays and searches for asymmetries among the decay products in the not-so-rare decays. Some examples for the rare decays are η 2π, η 4π 0 (CP tests), decays into an odd number of photons (e.g., η 3γ) and the decay η π 0 e e ¡ (C tests). In the conversion decay η π π ¡ e e ¡ , the asymmetry in the distribution of the angle between the two-pion and two-lepton decay planes allows to search for CP violation in a flavor-conserving process beyond the CKM mechanism which is not constrained by the limits on the neutron dipole moment. In addition, the Dalitz decays and the decays into a lepton-antilepton pair are sensitive to contributions from a vector boson responsible for the annihilation of hypothetical light dark matter particles. The muon g ¡ 2 and the branching ratio for the π 0 e e ¡ decay are currently the observables where hints of a deviation from the Standard Model predictions are reported. The experimental studies of the π 0 , η and η ½ meson decays are carried out at four European accelerator research facilities: KLOE/KLOE-2 at DAFNE (Frascati), Crystal Ball at MAMI (Mainz), WASA at COSY (Jülich), Crystal Barrel at ELSA (Bonn).

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Section: Tests Of C Symmetrymentioning

confidence: 94%