Where to find $X(17)$?

Abstract

The Atomki anomaly puts forward the hypothesis of an $X(17)$ particle to explain its observation. Utilizing experimental results from the Atomki experiments, measurements of the electron's anomalous magnetic moment, beam dump experiments, the KLOE-2 experiment, the PADME experiment, and the parity-violating Møller scattering experiment, we derive constraints on the $Xee$ coupling of the $X(17)$ boson to electrons. It is found that the scalar and pseudoscalar models can be excluded by Atomki experiments due to the parity conservation, and the pure axial-vector model is excluded at 98\% C.L. Meanwhile, the analyses in both pure vector and $V \pm A$ models consistently show that the $Xee$ coupling is of the vector type and has an almost fixed value, $\left(6.78 \pm 0.042\right) \times 10^{-4} \lesssim |\varepsilon_e^v| \lesssim \left(6.93 \pm 1.66\right) \times 10^{-4}$ in unit of electric charge $e$.