Signs, Spin, SMEFT: Sum Rules at Dimension Six

Abstract

We place theoretical constraints on the leading deviations to four-fermion standard model interactions. Invoking S-matrix analyticity and partial wave unitarity, we develop new dispersion relations that yield either spin-dependent sum rules on dimension-six fermionic operators or information about the amplitude's behavior at large momentum. The pattern of SMEFT inequalities we find for theories obeying certain large-momentum constraints enables a diagnosis of properties of emerging new physics. These relations form a bridge between new physics searches: discovery of flavor-violating $\tau$ decays at Belle II would motivate the search for flavor-conserving new physics below 25 TeV, as the results would provide definitive information about the UV.

10 pages, updated to published version

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Cited by in corpus (25)

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• Effective Field Theory Islands from Perturbative and Nonperturbative Four-Graviton Amplitudes
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• Two-Higgs Doublet Model Effective Field Theory
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• Positivity in Amplitudes and Quantum Entanglement
• Strings from Almost Nothing
• Positivity bounds in scalar-QED EFT at one-loop level
• Searching for the neutral triple gauge couplings in the process ${\mu }^{+}{\mu }^{-}\to \gamma \nu \bar{\nu }$ at muon colliders
• Probing Neutral Triple Gauge Couplings at e- p colliders