Little Higgs theory confronted with the LHC Higgs data

TL;DR

This study tests various little Higgs models against LHC Higgs data, finding that most models predict suppressed Higgs signals inconsistent with some experimental measurements, and that they do not improve the overall fit to data.

Contribution

It provides a comprehensive confrontation of several little Higgs models with current LHC Higgs data, highlighting their limitations and compatibility issues.

Findings

Most models predict suppressed diphoton and ZZ* signals.

The ZZ* signal rate aligns with experimental data within 1σ.

Diphoton signal rate often falls outside 2σ, especially in LHT-A.

Abstract

We confront the little Higgs theory with the LHC Higgs search data (up to 17 fb$^{-1}$ of the combined 7 and 8 TeV run). Considering some typical models, namely the littlest Higgs model (LH), the littlest Higgs model with T-parity (LHT-A and LHT-B) and the simplest little Higgs model (SLH), we scan over the parameter space in the region allowed by current experiments. We find that in these models the inclusive and exclusive (via gluon-gluon fusion) diphoton and $ZZ^*$ signal rates of the Higgs boson are always suppressed and approach to the SM predictions for a large scale $f$. Thus, the $ZZ^*$ signal rate is within the $1\sigma$ range of the experimental data while the inclusive diphoton signal rate is always outside the $2\sigma$ range. Especially, in the LHT-A the diphoton signal rate is outside the $3\sigma$ range of the experimental data for $f < 800$ GeV. We also perform a global $\chi^2$ fit to the available LHC and Tevatron Higgs data, and find that these models provide no better global fit to the whole data set (only for some special channels a better fit can be obtained, specially in the LHT-B).