Probing the relaxed relaxion and Higgs-portal with S1 & S2

Understand

We study the recent \XeT excess in context of solar scalar, specifically in the framework of Higgs-portal and the relaxion model.

• We show that $m_\phi = 1.9\,\keV$ and $g_{\phi e}=2.4\times 10^{-14}$ can explain the observed excess in science run 1 (SR1) analysis in the 1-7 keV range.
• When translated into the scalar-Higgs mixing angle, the corresponding mixing angle $\sin\theta = 10^{-8}$ is intriguingly close to the maximum value of mixing angle for the technical naturalness of the scalar mass.
• Unlike the solar axion model, the excess favors a massive scalar field because of its softer spectrum.