Constraints on non-standard contributions to the charged-current interactions

The success of the quantum level predictions of the Standard Model on the Z boson properties, on mW and on mt, which makes use of the muon lifetime as an input, implies a stringent constraint on new physics contributions to the V−A charged-current interactions among leptons. Observed unitarity of the CKM matrix elements then implies constraints on non-standard contributions to the lepton-quark charged-current interactions. By using the recent electroweak data as inputs, we find the 95% CL limits for the corresponding contact interactions: ΛCC,+ℓℓ>7.5 TeV and ΛCC,−ℓℓ>10.2 TeV for the purely leptonic terms, and ΛCC,+ℓq>5.8 TeV and ΛCC,−ℓq>10.1 TeV for the lepton-quark contact interactions.