Higgs Couplings and Naturalness

Understand

Many extensions of the Standard Model postulate the existence of new weakly coupled particles, the top partners, at or below the TeV scale.

• The role of the top partners is to cancel the quadratic divergence in the Higgs mass parameter due to top loops.
• We point out the generic correlation between naturalness (the degree of fine-tuning required to obtain the observed electroweak scale), and the size of top partner loop contributions to Higgs couplings to photons and gluons.
• If the fine-tuning is required to be at or below a certain level, a model-independent lower bound on the deviations of these Higgs couplings from the Standard Model can be placed (assuming no cancellations between contributions from various sources).