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Abstract:
We investigate neutrino interactions beyond the Standard Model of particle physics in
a model-independent framework. Considering general gauge- and Lorentz-invariant
operators composed of the known fundamental particles and hypothetical sterile neutrinos,
we review the effective field theory descriptions of interactions above and below
the weak scale with particular emphasis on neutrino interactions. Furthermore,
we identify gauge extensions, leptoquarks, as well as charged and neutral scalars as
potential origins of such new interactions which are consistent with our current observations
and can be tested through their traces in neutrino experiments or the direct
production of mediators at particle colliders. We survey experimental constraints on
effective neutrino interactions at energies below the weak scale, including an analysis
of the sensitivity of the DUNE and KATRIN experiments towards new interactions
in neutrino-electron scattering and tritium beta decay, respectively. We find that
if the new interactions are generated by gauge-invariant operators above the weak
scale, which would be expected if they originate from new physics at high energies,
neutrino interactions are more strongly constrained. The reason is that in this case
they are accompanied by additional interactions involving charged leptons which are
tested to greater precision. As an additional application of the framework, we show
that sterile neutrinos are phenomenologically viable candidates for dark matter when
identified as weakly interacting massive particles interacting through effective operators
with Standard Model fermions of the third generation. As we show for three
examples, explicit models generating these effective interactions can be distinguished
by producing the mediator particles at the Large Hadron Collider.
