COHERENT constraints to conventional and exotic neutrino physics

The process of neutral-current coherent elastic neutrino-nucleus scattering, consistent with the Standard Model (SM) expectation, has been recently measured by the COHERENT experiment at the Spallation Neutron Source. On the basis of the observed signal and our nuclear calculations for the relevant Cs and I isotopes, the extracted constraints on both conventional and exotic neutrino physics are updated. The present study concentrates on various SM extensions involving vector and tensor nonstandard interactions as well as neutrino electromagnetic properties, with an emphasis on the neutrino magnetic moment and the neutrino charge radius. Furthermore, models addressing a light sterile neutrino state and scenarios with new propagator fields—such as vector $Z^{\prime }$ and scalar bosons—are examined, and the corresponding regions excluded by the COHERENT experiment are presented.

Figure 1

Estimated number of events compared to the COHERENT experimental data.

Figure 2

$\mathrm{\Delta }{\chi }^2$ profile of the sensitivity to the weak mixing angle (see the text for details).

Figure 3

$\mathrm{\Delta }{\chi }^2$ profiles of vector (left panel) and tensor (right panel) NSI couplings, ${\epsilon }_{\alpha \alpha }^{qV}$ and ${\epsilon }_{\alpha \alpha }^{TV}$, respectively. Thick (thin) curves correspond to the ${\nu }_e$ (${\nu }_{\mu }+{\overline{\nu }}_{\mu }$) beam.

Figure 4

Allowed regions at 90% C.L. of the vector (upper panel) and tensor (lower panel) NSI parameters. The left (right) panel corresponds to the ${\nu }_e$ (${\nu }_{\mu }+{\overline{\nu }}_{\mu }$) beam. For comparison, the respective bounds are also presented by assuming a more simplistic sensitivity analysis for the case of vector NSIs. Only the limits corresponding to flavor-preserving nonuniversal couplings are shown, while the best-fit points in each case are denoted by an asterisk $\star$.

Figure 5

$\mathrm{\Delta }{\chi }^2$ profile of the sensitivity to the neutrino magnetic moment ${\mu }_{{\nu }_{\alpha }}$ (left panel) and to the neutrino charge radius $⟨r_{{\nu }_{\alpha }}^2⟩$ (right panel) from the analysis of the COHERENT data. Various interaction channels are examined (see the text).

Figure 6

Sensitivity regions at 90% C.L. from the analysis of the COHERENT data corresponding to the neutrino magnetic moment (left panel) and to the neutrino charge radius (right panel). The best-fit points are denoted by an asterisk $\star$.

Figure 7

Combined limits at 90% C.L. from the analysis of the COHERENT data for the cases of the weak mixing angle vs neutrino magnetic moment plane (left panel) and the neutrino charge radius vs neutrino magnetic moment plane (right panel). The best-fit points are denoted by an asterisk $\star$.

Figure 8

Exclusion curves at 90% C.L. from the analysis of the COHERENT data assuming sterile neutrinos in the $3+1$ scheme.

Figure 9

Limits to $Z^{\prime }$ vector mediator (left panel) and $\varphi$ scalar mediator (right panel) parameters at 90% C.L. The mediator masses are in units of MeV.