https://doi.org/10.1140/epjc/s10052-021-09670-z
Regular Article – Theoretical Physics
Confirming 
as a solution for 
with neutrinos
1
Institute for Particle Physics Phenomenology, Durham University, DH1 3LE, Durham, UK
2
Instituto de Física Teórica, Universidad Autónoma de Madrid, 28049, Madrid, Spain
3
Departamento de Física Teórica, Universidad Autónoma de Madrid, 28049, Madrid, Spain
4
Centre for Cosmology, Particle Physics and Phenomenology (CP3), Université Catholique de Louvain, Chemin du Cyclotron 2, 1348, Louvain-la-Neuve, Belgium
Received:
12
August
2021
Accepted:
17
September
2021
Published online:
1
October
2021
The recent measurement of the muon anomalous magnetic moment by the Fermilab E989 experiment, when combined with the previous result at BNL, has confirmed the tension with the SM prediction at 
CL, strengthening the motivation for new physics in the leptonic sector. Among the different particle physics models that could account for such an excess, a gauged stands out for its simplicity. In this article, we explore how the combination of data from different future probes can help identify the nature of the new physics behind the muon anomalous magnetic moment. In particular, we contrast with an effective 
-type model. We first show that muon fixed target experiments (such as NA64
) will be able to measure the coupling of the hidden photon to the muon sector in the region compatible with , and will have some sensitivity to the hidden photon’s mass. We then study how experiments looking for coherent elastic neutrino-nucleus scattering (CE
NS) at spallation sources will provide crucial additional information on the kinetic mixing of the hidden photon. When combined with NA64 results, the exclusion limits (or reconstructed regions) of future CENS detectors will also allow for a better measurement of the mediator mass. Finally, the observation of nuclear recoils from solar neutrinos in dark matter direct detection experiments will provide unique information about the coupling of the hidden photon to the tau sector. The signal expected for is larger than for with the same kinetic mixing, and future multi-ton liquid xenon proposals (such as DARWIN) have the potential to confirm the former over the latter. We determine the necessary exposure and energy threshold for a potential 
discovery of a boson, and we conclude that the future DARWIN observatory will be able to carry out this measurement if the experimental threshold is lowered to 
.
© The Author(s) 2021
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