XENON1T solar axion and the Higgs boson emerging from the dark
Chengfeng Cai, H. H. Zhang, Giacomo Cacciapaglia, Martin Rosenlyst, Mads T. Frandsen
Abstract
In a recent letter we proposed a new nonthermal mechanism of dark matter production based on vacuum misalignment, where both the Higgs boson and a very light pseudoscalar $\ensuremath{\eta}$ emerge from the dark sector. In this paper, we identify the parameter space in a composite scenario where the light pseudoscalar can be produced in the sun and explain the XENON1T excess in electron recoil data. The model's dark matter candidate has a mass around 50 TeV and out of range for direct detection. Testable predictions include gravitational waves at frequencies in the Hz range from a cosmological phase transition, an exotic decay $Z\ensuremath{\rightarrow}\ensuremath{\gamma}+\mathrm{inv}$ with rates $4\textdiv{}16\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}12}$ testable at a future Tera-Z collider, and an enhancement by $17\textdiv{}40%$ of the branching ratio ${K}_{L}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}+\mathrm{inv}$, not enough to explain the KOTO anomaly. All these predictions may be confirmed by future experiments.