New interference effects from light gauge bosons in neutrino-electron scattering

We point out that light gauge boson mediators could induce new interference effects in neutrino-electron scattering that can be used to enhance the sensitivity of neutrino-flavor-selective high-intensity neutrino experiments, such as Deep Underground Neutrino Experiment (DUNE). We particularly emphasize a destructive interference effect, leading to a deficit between the Standard Model expectation and the experimental measurement of the differential cross sections, which is prominent only in either the neutrino or the antineutrino mode, depending on the mediator couplings. Therefore, the individual neutrino (or antineutrino) mode could allow for sensitivity reaches superior to the combined analysis and, moreover, could distinguish between different types of gauge boson mediators.

Figure 1

Feynman diagrams of the SM processes (first and second) and the light gauge boson contribution (third) for the neutrino-electron elastic scattering. For the cases with antineutrinos in the parentheses, the arrow directions are assumed opposite.

Figure 2

90% C.L. sensitivity reaches of DUNE and ${\mathrm{JSNS}}^2$ experiments in the plane of the $B-L$ (left panel) or $L_e-L_{\mu }$ (right panel) gauge boson mass $m_V$ and its coupling strength, under the assumption of the exposures shown in the legends. We estimate the backgrounds using the number of neutrino-electron scattering events reported in Ref. [42] for DUNE and calculating the pure SM expectation for ${\mathrm{JSNS}}^2$. For DUNE, 5% systematics in the neutrino flux normalization is included, while ${\mathrm{JSNS}}^2$ is purely statistics based. The existing limits are shown by the gray-shaded region with experiments forming the boundaries explicitly mentioned in the figure. For comparison, the region preferred by the recently updated muon anomalous magnetic moment at $2\sigma$ [58] is shown as well. DUNE can be sensitive to the signal by a deficit (the regions encompassed by dot-dashed lines) originating from a sizable destructive interference effect. See the text for details.