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The Constrained Electroweak Chiral Lagrangian

Abstract:

In the framework of the effective field theory method, we use the experimental data and the perturbative unitarity bounds to determine the values and uncertainty of all the 11 chiral coefficients ($\al_i, i=0, ..., 10$) of the standard electroweak chiral Lagrangian. Up to linear terms in $\al_i$, we provide the one-loop renormalization group equations of all the chiral coefficients, which are calculated in the Feynman-'t Hooft gauge using the modified minimal subtraction scheme. With the improved renormalization group equations to sum over the logarithmic corrections, we analyze the current experimental uncertainty of oblique correction parameters, $S(\Lambda) and $T(\Lambda)$. We find that, due to the large uncertainty in the triple gauge-boson coupling measurements, the parameter space of positive $S(\Lambda)$ for $\Lambda > 1$ TeV is still allowed by the current experimental data. $T(\Lambda)$ tends to increase with $\Lambda$ even in the presence of the operators that contribute to the triple and quartic gauge-boson couplings.