New Physics bounds from the combination of CKM-universality and high energy data

TL;DR

This paper uses an effective field theory approach to set new physics bounds based on CKM unitarity and high-energy data, constraining operators to scales above 11 TeV.

Contribution

It introduces a novel analysis linking CKM unitarity violations to new physics operators with bounds comparable to Z pole measurements.

Findings

Delta_CKM bound constrains new physics operators

Effective scale > 11 TeV at 90% CL

Constraints comparable to Z pole observables

Abstract

Through an effective field theory approach, we analyze the new physics corrections to muon and beta decays and their effects on the extractions of V_ud and V_us. Assuming nearly flavor blind NP interactions, we find that the only quantity sensitive to NP is Delta_CKM = |V_ud|^2 + |V_us|^2 + |V_ub|^2 - 1, that receives contributions from four short distance operators. The phenomenological bound Delta_CKM = (-1 \pm 6) 10^-4 provides strong constraints on all four operators, corresponding to an effective scale Lambda > 11 TeV (90% CL). Depending on the operator, this constraint is at the same level or better than that generated by the Z pole observables.