Abstract
The anomalies recently reported in lepton pair transitions of $^8$Be$^*$ and $^4$He nuclei may be attributed to the existence of a feebly interacting light vector boson $X17$. We study the effects of this hypothetical particle in the semileptonic $H^* \to H e^+e^-$ decays ($H$ a $Q\bar{q}$ meson) in the framework of the HQET+VMD model. Using current bounds and the universality assumption of the $X17$ boson to quarks, we find that decays of $D^{*+}$ and $D_s^{*+}$ mesons can be importantly enhanced relative to the dominant photon-mediated contributions. Dedicated experimental searches at current heavy meson factories may confirm the existence of this light boson or set stronger bounds of their couplings to ordinary matter.
Highlights
The existence of a light vector boson weakly coupled to Standard Model (SM) fermions has been suggested as a solution to the observed discrepancy between the SM prediction and the experimental measurement of the muon g − 2 magnetic moment anomaly
The anomalies recently reported in lepton pair transitions of 8Beà and 4He nuclei may be attributed to the existence of a feebly interacting light vector boson X17
The hypothetical light vector boson X17, proposed as a solution for the anomaly observed in lepton-pair production of 8Beà and 4He transitions, can be studied in the clean environment provided by vector to pseudoscalar heavy mesons transitions in Belle, Belle II [28], and BESIII factories
Summary
The existence of a light vector boson weakly coupled to Standard Model (SM) fermions has been suggested as a solution to the observed discrepancy between the SM prediction and the experimental measurement of the muon g − 2 magnetic moment anomaly (see for example [1,2]). It may be a good candidate as a mediator of dark and ordinary matter interactions [1,2]. HÃ → Heþe− decays seem to be interesting to further test the Atomki anomaly: on the one hand, the mass splitting in heavy mesons is large enough (see Table I) to produce the X17 boson on shell; on the
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