Light custodians in natural composite Higgs models
Roberto Contino, Leandro Da Rold, Alex Pomarol
TL;DR
The paper addresses natural electroweak symmetry breaking in warped extra-dimensional models by constructing a class of composite Higgs scenarios with custodial symmetry, embedding SM fermions in SO(5) representations 5 or 10 and enlarging the IR symmetry to O(4). It shows that top-quark compositeness induces EWSB and predicts a light set of custodians with charges 5/3, 2/3, and -1/3, whose masses lie in the few-hundred GeV to ~1.5 TeV range, while KK gauge bosons lie around 2–3 TeV. The analysis uses a holographic effective field theory to compute the one-loop Higgs potential and maps the viable parameter space under EWPT constraints, highlighting the correlation between the Higgs mass and the custodian spectrum. The custodians provide a distinctive LHC signature and serve as a diagnostic to distinguish 5D composite Higgs scenarios from other EWSB mechanisms, with Higgs mass predicted in the ~115–190 GeV range and potential discovery prospects at the LHC.
Abstract
We present a class of composite Higgs models arising from a warped extra dimension that can satisfy all the electroweak precision tests in a significant portion of their parameter space. A custodial symmetry plays a crucial role in keeping the largest corrections to the electroweak observables below their experimental limits. In these models the heaviness of the top quark is not only essential to trigger the electroweak symmetry breaking, but it also implies that the lowest top resonance and its custodial partners, the custodians, are significantly lighter than the other resonances. These custodians are the trademark of these scenarios. They are exotic colored fermions of electromagnetic charges 5/3, 2/3 and -1/3, with masses predicted roughly in the range 500-1500 GeV. We discuss their production and detection at the LHC.