Abstract
Neutrino oscillations are precision probes of new physics. Apart from neutrino masses and mixings, they are also sensitive to possible deviations of low-energy interactions between quarks and leptons from the Standard Model predictions. In this paper we develop a systematic description of such non-standard interactions (NSI) in oscillation experiments within the quantum field theory framework. We calculate the event rate and oscillation probability in the presence of general NSI, starting from the effective field theory (EFT) in which new physics modifies the flavor or Lorentz structure of charged-current interactions between leptons and quarks. We also provide the matching between the EFT Wilson coefficients and the widely used simplified quantum-mechanical approach, where new physics is encoded in a set of production and detection NSI parameters. Finally, we discuss the consistency conditions for the standard NSI approach to correctly reproduce the quantum field theory result.
Highlights
To combine and compare the obtained bounds with other probes that are sensitive to the same non-standard interactions
We provide the matching between the effective field theory (EFT) Wilson coefficients and the widely used simplified quantum-mechanical approach, where new physics is encoded in a set of production and detection non-standard interactions (NSI) parameters
The neutral-current NSI other than the matter effects can be correctly described by quantum field theory (QFT) expressions analogous to eqs. (2.1)–(2.3), and they are relevant e.g. if neutrinos are detected via coherent scattering on nuclei
Summary
Oscillation probability can be rigorously derived in the framework of quantum field theory. The production and detection can be described by QFT amplitudes MPαk ≡ M(S → Xανk) and MDβk ≡ M(νkT → Yβ), where the index k labels neutrino mass eigenstates. The phase space elements dΠP and dΠD for the production and detection processes are defined in the standard way: dΠ ≡. One can define the να → νβ oscillation probability as the ratio of the rate of detected events in eq (2.1) to the no-oscillation expression in eq (2.2), finding. Oscillation probability is an intuitive and widely employed concept, strictly speaking Pαβ is not an observable For this reason in this paper we work mainly with the rate in eq (2.1).
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