An experimental test of how frequently neutrinos interact with atomic nuclei has a best fit value of the Standard Model expectation and an uncertainty of less than ± 15%, which is impressive given how slight the interaction is, fit 10^22 trials yielding just 124 observed interactions.
The COHERENT collaboration reports the most precise measurement of the coherent elastic neutrino-nucleus scattering cross section to date. This measurement was performed with COHERENT's germanium detector array, Ge-Mini, at the Spallation Neutron Source at Oak Ridge National Laboratory.
A cumulative exposure of 4.68 × 10^22 protons on target yielded a total number of observed counts of 124 + 14 −12 and a flux-averaged cross section of 1.00 ± 0.10 (statistical) ± 0.10 (systematic) relative to the standard-model expectation of 5.9 × 10^−39 cm^2.
The well-understood energy and timing distributions of the neutrino source allow for independent measurements of muon- and electron-neutrino scattering rates. This information is used to improve constraints on non-standard neutrino interactions mediated by heavy particles.
M. Adhikari, et al., "Measurement of coherent elastic neutrino nucleus scattering on germanium by COHERENT" arXiv:2603.17951 (March 18, 2026).
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High Energy Physics - Phenomenology
[Submitted on 16 Mar 2026]
Glimpses of the X17 from coherent elastic neutrino nucleus scattering
Johan Rathsman, Joakim Cederkäll, Yasar Hicyilmaz, Else Lytken, Stefano Moretti
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.
Comments: 28 pages, 12 figures
Subjects: High Energy Physics - Phenomenology (hep-ph)
Cite as: arXiv:2603.15246 [hep-ph]
Conclusions and outlook
By analysing nuclear recoil spectra arising from CEνNS utilising electron anti-neutrinos from
nuclear reactors and adding a light vector mediator in the form a Z′ boson, we have shown
that the data from the CONUS+ and Dresden-II experiments point to a preferred mass region
(around 16.7 MeV) close to that of the X17, which has emerged as a possible explanation of
the ATOMKI anomaly. In fact, including the X17 also makes it possible to resolve the tension
between the CONUS+ and Dresden-II data. The difference in the observations between the
two experiments is then to a large extent explained by the differences in detector resolution
which gives a different sensitivity to the X17.
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