Speaker
Description
The recent ATOMKI experiments provided evidence pointing towards the existence of an X17 boson in the anomalous nuclear transitions of Beryllium-8, Helium-4, and Carbon-12. The favored ranges for the couplings between the X17 boson and the first-generation quarks, denoted as $\epsilon_u$ and $\epsilon_d$, are determined through fittings to the above nuclear transitions.
In this work, we consider X17 boson contributions to the previously measured D meson decays which include $D_s^{*+} \rightarrow D_s^+ e^+ e^-$, $D_s^{*+} \rightarrow D_s^+ \gamma$, $D^{*0} \rightarrow D^0 e^+ e^-$, and $D^{*0} \rightarrow D^0 \gamma$, as well as the measured decays of $\psi(2S) \rightarrow \eta_c e^+ e^-$, $\psi(2S) \rightarrow \eta_c \gamma$, $\phi \rightarrow \eta e^+ e^-$, and $\phi \rightarrow \eta \gamma$. In addition to the dependence on $\epsilon_u$, these decays also depend on X17 boson couplings to the second-generation quarks, denoted as $\epsilon_c$ and $\epsilon_s$. Using the data of the above meson decays, we perform an independent fitting to the coupling parameters $\epsilon_u$, $\epsilon_c$, and $\epsilon_s$ while keeping the X17 boson mass at the best-fit value obtained by ATOMKI experiments. In this fitting, we take the scenario that X17 is a vector boson and treat the couplings $\epsilon_u$ and $\epsilon_c$ as independent from each other rather than assuming the generation universality $\epsilon_u =\epsilon_c$. It is found that the above fitting renders a huge magnitude for $\epsilon_u$, which is in serious tension with $\epsilon_u$ determined from the ATOMKI measurements of Beryllium-8, Helium-4, and Carbon-12 nuclear transitions. Implications of our findings are discussed.
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