Glimpses of the X17 from coherent elastic neutrino nucleus scattering

TL;DR

This paper demonstrates that coherent elastic neutrino-nucleus scattering experiments can probe the X17 particle, potentially explaining the ATOMKI anomaly, and shows data compatibility with the X17 hypothesis over the Standard Model.

Contribution

It provides the first analysis of CEvNS data in relation to the X17 particle, suggesting experimental sensitivity and compatibility with the anomaly's proposed properties.

Findings

CONUS+ and Dresden-II data favor the X17 hypothesis

Adding COHERENT data refines the preferred coupling regions

Results indicate CEvNS experiments can test the X17 particle hypothesis

Abstract

We show that the process of Coherent Elastic neutrino (v) Nucleus Scattering (CEvNS) at nuclear reactor experiments has significant sensitivity to the so-called X17 particle, which has been invoked to explain the ATOMKI anomaly, wherein electron-positron pairs emerging from a nuclear transition of excited Be-8, He-4 and C-12 nuclei are studied. Such a new state has potentially been identified as a spin-1 object, with axial-vector couplings and a mass around 16.7 MeV, hence, in the kinematic range accessible by the aforementioned experimental settings. Specifically, we fit CONUS+ and Dresden-II data and show that a robust statistical analysis renders these more compatible with the X17 hypothesis, in turn interfering with the Standard Model, than with that of the latter alone. The same stays true when also adding COHERENT data from pi+ decays at rest, singling out two regions of preferred couplings of the X17 to electron and muon neutrinos as well as nuclei.