Light top partners and precision physics

Understand

We analyze the corrections to the precision EW observables in minimal composite Higgs models by using a general effective parametrization which also includes the lightest fermionic resonances.

• A new, possibly large, logarithmically divergent contribution to S is identified, which comes purely from the strong dynamics.
• It can be interpreted as a running of S induced by the non-renormalizable Higgs interactions due to the non-linear sigma-model structure.
• As expected, the corrections to the T parameter coming from fermion loops are finite and dominated by the contributions of the lightest composite states.