New Physics bounds from CKM-unitarity
arXiv:1101.4679
Abstract
Using an effective field theory approach, we study the new physics (NP) 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 CKM-unitarity test is the only way to expose NP. The four short-distance operators that can generate a deviation are strongly constrained by the phenomenological bound |Vud|^2 + |Vus|^2 + |Vub|^2 - 1 = (-0.0001 \pm 0.0006), corresponding to an effective scale > 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.
To appear in the proceedings of the 45th Rencontres de Moriond: Electroweak Interactions and Unified Theories, La Thuile, Aosta Valley, Italy, 6-13 Mar 2010