Abstract
The presence of new neutrino-quark interactions can enhance, deplete or distort the coherent elastic neutrino-nucleus scattering (CEνNS) event rate. The new interactions may involve CP violating phases that can potentially affect these features. Assuming light vector mediators, we study the effects of CP violation on the CEνNS process in the COHERENT sodium-iodine, liquid argon and germanium detectors. We identify a region in parameter space for which the event rate always involves a dip and another one for which this is never the case. We show that the presence of a dip in the event rate spectrum can be used to constraint CP violating effects, in such a way that the larger the detector volume the tighter the constraints. Furthermore, it allows the reconstruction of the effective coupling responsible for the signal with an uncertainty determined by recoil energy resolution. In the region where no dip is present, we find that CP violating parameters can mimic the Standard Model CEνNS prediction or spectra induced by real parameters. We point out that the interpretation of CEνNS data in terms of a light vector mediator should take into account possible CP violating effects. Finally, we stress that our results are qualitatively applicable for CEνNS induced by solar or reactor neutrinos. Thus, the CP violating effects discussed here and their consequences should be taken into account as well in the analysis of data from multi-ton dark matter detectors or experiments such as CONUS, ν-cleus or CONNIE.
Highlights
The Standard Model (SM) CEνNS cross section proceeds through a neutral current process [17, 18].1 Depending on the target nucleus, in particular for heavy nuclei, it can involve sizable uncertainties arising mainly from the root-mean-square radius of the neutron density distribution [20]
We have considered the effects of CP violating parameters on CEνNS processes, and for that aim we have considered light vector mediator scenarios
In contrast to light scalar mediator schemes, light vector mediators allow for interference between the SM and the new physics, something that we have shown enables the splitting of the parameter space into two non-overlapping sectors in which CP violating effects have different manifestations: (i)
Summary
Our analysis is done assuming that the new physics corresponds to the introduction of light vector mediators This choice has to do with phenomenological constraints. Fn,p(q2) are the neutron and proton nuclear form factors obtained from the Fourier transform of the nucleonic density distributions (in the first Born approximation) Note that this differentiation is relevant for nuclides with N > Z, such as sodium, argon or germanium [20]. Typical nuclear form factors parametrizations depend on two parameters which are constrained via the corresponding nucleonic density distribution root-mean-square (rms) radii. In general the analysis of CP violating effects is a nine parameter problem: the vector boson mass, four moduli and four CP phases.
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