Signatures of $X_{17}$ through Coherent Elastic Solar Neutrino-Nucleus Scattering in Direct Detection Searches

Abstract

The $X_{17}$ particle has been proposed to explain the invariant mass anomalies observed in electron-positron pairs during nuclear transitions at the Atomki experiment. Motivated by recent observations of ${}^8$B solar neutrinos induced coherent elastic neutrino-nucleus scattering (CE$\nu$NS), we present the first comprehensive analysis of the hypothetical boson using data from multi-ton dark matter direct detection facilities. We consider the new particle as a light $Z^{\prime }$ mediator arising from a spontaneously broken $U(1{)}^{\prime }$ symmetry, featuring both vector and axial-vector couplings to leptons. By evaluating the latest datasets from XENONnT, PandaX-4T, and LUX-ZEPLIN, we derive stringent limits on the effective vector coupling utilizing marginalization procedures. Our global analysis provides competitive constraints that meaningfully narrow the allowed parameter space of the model, while exhibiting a clear sensitivity to the tau-flavor coupling.

Comments: 19 pages, 10 figures and 1 table