Constraints on Non-Standard Contributions to the Charged-Current Interactions

Abstract

The success of the quantum level predictions of the Standard Model on the $Z$ boson properties, on $\text{mw}$ and on $\text{mt}$, 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: ${\Lambda }_{CC,+}^{\ell \ell }>7.5$ TeV and ${\Lambda }_{CC,-}^{\ell \ell }>10.2$ TeV for the purely leptonic terms, and ${\Lambda }_{CC,+}^{\ell q}>5.8$ TeV and ${\Lambda }_{CC,-}^{\ell q}>10.1$~TeV for the lepton-quark contact interactions.

Comments: 11 pages, Latex, 1 figure, added a few references