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Coloma, P., Fernandez-Martinez, E., Gonzalez-Lopez, M., Hernandez-Garcia, J., & Pavlovic, Z. (2021). GeV-scale neutrinos: interactions with mesons and DUNE sensitivity. Eur. Phys. J. C, 81(1), 78–24pp.
Abstract: The simplest extension of the SM to account for the observed neutrino masses and mixings is the addition of at least two singlet fermions (or right-handed neutrinos). If their masses lie at or below the GeV scale, such new fermions would be produced in meson decays. Similarly, provided they are sufficiently heavy, their decay channels may involve mesons in the final state. Although the couplings between mesons and heavy neutrinos have been computed previously, significant discrepancies can be found in the literature. The aim of this paper is to clarify such discrepancies and provide consistent expressions for all relevant effective operators involving mesons with masses up to 2 GeV. Moreover, the effective Lagrangians obtained for both the Dirac and Majorana scenarios are made publicly available as FeynRules models so that fully differential event distributions can be easily simulated. As an application of our setup, we numerically compute the expected sensitivity of the DUNE near detector to these heavy neutral leptons.
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Fernandez-Martinez, E., Gonzalez-Lopez, M., Hernandez-Garcia, J., Hostert, M., & Lopez-Pavon, J. (2023). Effective portals to heavy neutral leptons. J. High Energy Phys., 09(9), 001–45pp.
Abstract: The existence of right-handed neutrinos, or heavy neutral leptons (HNLs), is strongly motivated by the observation of neutrino masses and mixing. The mass of these new particles could lie below the electroweak scale, making them accessible to lowenergy laboratory experiments. Additional new physics at high energies can mediate new interactions between the Standard Model particles and HNLs, and is most conveniently parametrized by the neutrino Standard Model Effective Field Theory, or nu SMEFT for short. In this work, we consider the dimension six nu SMEFT operators involving one HNL field in the mass range of O(1) MeV < MN < O(100) GeV. By recasting existing experimental limits on the production and decay of new light particles, we constrain the Wilson coefficients and new physics scale of each operator as a function of the HNL mass.
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