This report summarizes the present status of neutrino non-standard interactions (NSI). After a brief overview, several aspects of NSIs are discussed, including connection to neutrino mass models, model-building and phenomenology of large NSI with both light and heavy mediators, NSI phenomenology in both short- and long-baseline neutrino oscillation experiments, neutrino cross-sections, complementarity of NSI with other low- and high-energy experiments, fits with neutrino oscillation and scattering data, DUNE sensitivity to NSI, effective field theory of NSI, as well as the relevance of NSI to dark matter and cosmology. We also discuss the open questions and interesting future directions that can be pursued by the community at large. This report is based on talks and discussions during the Neutrino Theory Network NSI workshop held at Washington University in St.~Louis from May 29-31, 2019

Novel leptophilic neutral currents can be tested at upcoming neutrino oscillation experiments using two complementary processes, neutrino trident production and neutrino-electron (ν − e) elastic scattering. Considering generic anomaly-free Uð1Þ extensions of the Standard Model, we discuss the characteristics of ν − e scattering as well as e þ e − and μ þ μ − trident production at the DUNE near detector in the presence of such beyond the Standard Model scenarios. We then determine the sensitivity of DUNE in constraining the well-known L e − L μ and L μ − L τ models. We conclude that DUNE will be able to probe these leptophilic models with unprecedented sensitivity, covering unproved explanations of the ðg − 2Þ μ discrepancy.

Neutrino trident scattering is a rare Standard Model process where a chargedlepton pair is produced in neutrino-nucleus scattering. To date, only the dimuon final-state has been observed, with around 100 total events, while the other channels are as yet unexplored. In this work, we compute the trident production cross section by performing a complete four-body phase space calculation for different hadronic targets. This provides a correct estimate both of the coherent and the diffractive contributions to these cross sections, but also allows us to address certain inconsistencies in the literature related to the use of the Equivalent Photon Approximation in this context. We show that this approximation can give a reasonable estimate only for the production of dimuon final-states in coherent scattering, being inadmissible for all other cases considered. We provide estimates of the number and distribution of trident events at several current and future near detector facilities subjected to intense neutrino beams from accelerators: five liquid-argon detectors (SBND, µBooNE, ICARUS, DUNE and νSTORM), the iron detector of T2K (INGRID) and three detectors made of composite material (MINOS, NOνA and MINERνA). We find that for many experiments, trident measurements are an attainable goal and a valuable addition to their near detector physics programme.

We study Primordial Black Holes (PBHs) as sources of massive neutrinos via Hawking radiation. Under the hypothesis that black holes emit neutrino mass eigenstates, we describe quantitatively how the PBH evolution and lifetime is affected by the mass and fermionic—Dirac or Majorana—nature of neutrinos. In the case of Dirac neutrinos, PBHs radiate right-handed and left-handed neutrinos in equal amounts, thus possibly increasing the effective number of neutrino species, Neff. Assuming an initially monochromatic PBH mass spectrum, with the initial mass Mi related to the particle horizon mass, and considering the current constraint on Neff, we derive a bound on the initial PBH fraction β′ in the interval 4.3× 107 g≲ Mi ≲ 109 g. Future measurements of Neff may be able to constraint the initial fraction for black hole masses as low as 1 g. If an excess in Neff is found, PBHs with Dirac neutrinos could provide a minimal explanation of it. For example, for 107 g ≲ Mi≲ 109 g and β′ ≳ 10−13, an excess radiation at the level of 0.2≲ Δ Neff≲ 0.37 is produced, which can alleviate the tension of the Hubble parameter measurements. Finally, we obtain the diffuse flux of right-helical neutrinos from PBHs at the Earth, and show that their detection in a PTOLEMY-like detector (using neutrino capture on tritium) would be difficult.