Yu-Han Zhao | Searcharxiv

arXiv2026

Where to find $X(17)$?

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 M{\o}ller 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 the vector $\pm$ axial-vector 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 $e$.

hep-ph↗

arXiv2022

Production of double heavy quarkonium at super $Z$ factory

Within the color singlet model, we calculate the exclusive production of double charmonia, double bottomonia, and double $B_c$ mesons at future super $Z$ factory. The two heavy quarkonia or $B_c$'s are either two S-wave Fock states ($^1S_0, ~^3S_1$), or one S-wave and one P-wave states ($^1P_1,~^3P_J~(J=0,1,2)$). The top three $Z^0$ propagated channels in cross sections for double charmonia are $J/\psi+h_c,\eta_c+\chi_{c2}$, and $\eta_c+\chi_{c0}$. For double bottomonia, they are $\eta_b+\Upsilon, \Upsilon+\chi_{b2}$, and $\Upsilon+\Upsilon$. For double $B_c$ mesons, they are $B_c^{*+}+B_c^{*-}$,$B_c^{*+}+\chi_{bc2}^-$, and $\eta_{bc}^++B_c^{*-}$. The cross sections of double $B_c$ mesons are roughly one order of magnitude larger than those of the double bottomonia, and two orders of magnitude larger than those of the double charmonia. To make it helpful for experimental study, we present the total cross sections $\sigma$ as functions of CM energy $\sqrt{s}$, $\sigma$ as functions of the renormalization scale $\mu$, the angle distributions $d\sigma/dcos\theta$, and the $p_T$ distributions $d\sigma/dp_{t}$. The uncertainties come from the varying masses of constituent heavy quarks bring up to 20% corrections. We also find that the initial state radiation can bring about 30%$\sim$40% suppresions when 1\%$m_Z$ energy is losing, and cross sections can increase by about $2\sim3$ times or decrease by an order of magnitude when adopting different potential models which becomes the major source of uncertainty. The numerical results show that it might be not optimistic for the experimental observation, but it is still far from excluded at the FCC-ee and also the CEPC running in the $Z$ factory mode.

hep-ph↗