Abstract
The Atomki collaboration has reported that unexpected excesses have been observed in the rare decays of Beryllium nucleus. It is claimed that such excesses can suggest the existence of a new boson, called X, with the mass of about 17 MeV. To solve the Atomki anomaly, we consider a model with gauged U(1)R symmetry and identify the new gauge boson with the X boson. We also introduce two SU(2) doublet Higgs bosons and one singlet Higgs boson, and discuss a very stringent constraint from neutrino-electron scattering. It is found that the U(1)R charges of the doublet scalars are determined to evade the constraint. In the end, we find the parameter region in which the Atomki signal and all experimental constraints can be simultaneously satisfied.
Highlights
Bumps can be well fitted simultaneously under the assumption that a hypothetical boson X with the mass of 17.01 ± 0.16 and 19.68 ± 0.25 MeV is produced through 8Be∗ and 4He decays, followed by X decay into a e+-e− pair, respectively
The other advantage is that the partial decay width of 8Be∗ is proportional to kX,1 the X’s three momentum, while it is proportional to kX3 in the vector boson hypothesis
A contribution to neutral pion decay from vectorial interactions is much suppressed. It was shown in [37, 38] that flavour changing neutral currents can be suppressed due to U(1)R symmetry in two Higgs doublet extension. It was shown in [39,40,41,42,43] that neutrino masses and mixing, dark matter and the muon anomalous magnetic moment can be explained in models with the U(1)R gauge symmetry
Summary
Higgs scalars, is flavour changing meson decays with radiating the longitudinal mode of the X boson such as K → πX, B → KX via a charged Higgs boson loop It was pointed out in [59, 60] that such decays in a U(1)R model [61] are enhanced, and the constraints from these show a tension with the Atomki signal, unless all of the decay modes are suppressed by fine-tunings. Relevant to the Atomki signal, and assume that the parameters in the scalar potential are appropriately chosen so that the new gauge boson acquires the mass required to explain the Atomki anomaly
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