A Higgs Conundrum with Vector Fermions

TL;DR

This paper investigates models with heavy vector fermions and finds that, within experimental constraints, their effects on Higgs production and decay are nearly indistinguishable from the Standard Model, making new physics hard to detect.

Contribution

It analyzes the impact of heavy vector fermions on Higgs processes and shows these models are consistent with precision measurements while closely mimicking the Standard Model.

Findings

Higgs production and decay rates are close to Standard Model predictions.

Models with vector fermions are difficult to distinguish from the Standard Model.

Decoupling properties of vector fermions are crucial for their experimental signatures.

Abstract

Many models of Beyond the Standard Model physics involve heavy colored fermions. We study models where the new fermions have vector interactions and examine the connection between electroweak precision measurements and Higgs production. In particular, for parameters which are allowed by precision measurements, we show that the gluon fusion Higgs cross section and the Higgs decay branching ratios must be close to those predicted by the Standard Model. The models we discuss thus represent scenarios with new physics which will be extremely difficult to distinguish from the minimal Standard Model. We pay particular attention to the decoupling properties of the vector fermions.