Top Partners in Little Higgs Theories with T-parity

TL;DR

The paper demonstrates a realization of T-parity in little Higgs theories where every particle canceling the one-loop Higgs quadratic divergence, including a heavy top partner, is T-odd. This leads to a simplified top-sector with no $t$–$T^c$ mixing and a divergence cancellation governed by $\lambda_T' = \lambda_t^2 + \lambda_T^2$, with $m_T = \sqrt{2}\lambda f$ and $\lambda_T = 0$, $\lambda_T' = 4\lambda^2$. Electroweak corrections remain loop-suppressed, enabling relatively low $f$ scales and reducing tension with precision data. At the LHC, all T-odd states are pair-produced, producing missing-energy signatures reminiscent of SUSY, complicating discrimination but offering a rich testing ground. The authors provide explicit model constructions and discuss strategies to distinguish these scenarios from supersymmetry via mass spectra and detailed collider kinematics.

Abstract

We consider a class of little Higgs theories with T-parity where ALL new particles responsible for canceling the standard model contributions to the one-loop quadratic divergences in the Higgs potential are odd under T-parity, including the heavy top partner which was previously taken to be T-even. The new construction significantly simplifies the spectrum in the top sector and completely changes the phenomenology of the top partner. At hadron colliders the signals of this class of T-invariant models appear to be even more similar to supersymmetry. We initiate a study on the collider phenomenology and discuss the challenge of distinguishing this class of models from supersymmetry at the Large Hadron Collider.

Figures (5)

• Figure 1: Cancellation of top quadratic divergences.
• Figure 2: Generation of type ${\rm (II)}^\prime$ and ${\rm (III)}^\prime$ vertices by integrating out the mirror fermions.
• Figure 3: Examples of diagrams contributing to $\rho$ parameters and $Zb\bar{b}$ vertex.
• Figure 4: Production cross sections of$T$at the LHC as a function of its mass (solid line). For comparison, we also plot the production cross section of$\tilde{t}_R$in SUSY.
• Figure 5: Comparison between$T$and$\tilde{t}_R$. $\kappa=m_{A_H}/m_T$ or $\kappa=m_{\rm LSP}/m_{\tilde{t}_R}$.