Higgs-pair Production in Littlest Higgs Model with T-parity

TL;DR

The paper tackles Higgs-pair production at the LHC as a probe of the Higgs self-coupling within the Littlest Higgs framework endowed with T-parity. It performs a comprehensive one-loop calculation incorporating both T-even and T-odd quark contributions to gg→hh, and compares hadronic cross sections to SM and MSSM expectations using standard parton distributions and LoopTools for loop integrals. The main finding is a substantial enhancement of the gg→hh cross section relative to the SM, with the T-odd quark sector contributing comparably to the T-even sector; the effect is sensitive to the symmetry-breaking scale f and the ratio r. This work underscores the importance of including T-odd states in collider phenomenology and provides predictions that could guide LHC Higgs self-coupling tests within this model class.

Abstract

The Higgs-pair production process at the CERN Large Hadron Collider (LHC), which will provide a way to test the Higgs boson self-coupling, may be sensitive to new physics. In the framework of the littlest Higgs model with T-parity, such Higgs-pair production can proceed through additional loop diagrams and thus the production rate can be quite different from the Standard Model (SM) prediction. Our calculations show that, due to the loop contributions of both T-even and T-odd quarks predicted in this model, the production rate can be significantly enhanced relative to the SM prediction and also can be larger than the production rate in the minimal supersymmetric model. Also, we find that the T-odd quark contributions, which were ignored in a previous study, are equally important compared with the T-even quark contributions.

Figures (3)

• Figure 1: The parton-level Feynman diagrams for Higgs-pair production via gluon-gluon fusion in the littlest Higgs model with T-parity. Here $f_i$ can be a T-even fermion ($i=1, 2$ with $f_1=t$ and $f_2=T$) or a T-odd fermion ($i=1, 2 ,3$ with $f_1=u_-$, $f_2=\chi$ and $f_3=q$). The diagrams obtained by exchanging the two gluons or exchanging the two Higgs bosons are not shown here.
• Figure 2: Hadronic Higgs-pair production cross section at the LHC versus the parameter $f$. The supersymmetric model prediction is taken from Fig. 5(a) in the first reference of ref6.
• Figure 3: Same as Fig.2, but show the results with and without the contributions of the T-odd quarks for $r=1.0$.