Abstract
We study constraints on the Standard Model Effective Field Theory (SMEFT) from neutrino oscillations in short-baseline reactor experiments. We calculate the survival probability of reactor antineutrinos at the leading order in the SMEFT expansion, that is including linear effects of dimension-6 operators. It is shown that, at this order, reactor experiments alone cannot probe charged-current contact interactions between leptons and quarks that are of the (pseudo)vector (V±A) or pseudo-scalar type. We also note that flavor-diagonal (pseudo)vector coefficients do not have observable effects in oscillation experiments. In this we reach novel or different conclusions than prior analyses of non-standard neutrino interactions. On the other hand, reactor experiments offer a unique opportunity to probe tensor and scalar SMEFT operators that are off-diagonal in the lepton-flavor space. We derive constraints on the corresponding SMEFT parameters using the most recent data from the Daya Bay and RENO experiments.
Highlights
The reactor experiments alone are not sensitive to new physics parametrized by [ L]eμ and [ L]eτ, as these parameters can be absorbed into the unknown mixing angle θ13, and only the θ13 combination defined in eq (3.13) is probed
We have proposed a systematic approach to neutrino oscillations in the situation when neutrino interactions with matter are modified by heavy new physics
To this end we employed the model-independent framework of the Standard Model Effective Field Theory (SMEFT), with the Lagrangian organized into an expansion in powers of 1/Λ, where Λ is the mass scale of new particles affecting the neutrino interactions
Summary
New effective 4-fermion interactions between leptons and quarks may give observable effects in neutrino production, propagation, and detection, and they can be constrained by experiment. Consistent EFTs come with an expansion parameter, and the Lagrangian, amplitudes, and observables can be systematically constructed order by order in that expansion This allows one to compare different NSI effects in neutrino oscillations, and unambiguously identify the leading order contributions. Given the SMEFT Lagrangian, we derive the effective charged-current interactions between neutrinos, charged leptons, and nucleons in the low-energy EFT relevant for reactor experiments. At the leading order in the SMEFT expansion, NSI interactions diagonal in the lepton-flavor space are currently not probed by oscillation experiments. Reactor experiments show an interesting sensitivity to off-diagonal tensor and scalar NSI, which were neglected in most prior studies
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