Color-octet scalar effects on Higgs boson production in gluon fusion

TL;DR

The paper investigates how a color-octet scalar (8,1)_0 can modify Higgs production via gluon fusion at NNLO in QCD using an effective theory that integrates out the heavy top quark and scalar. It derives a compact analytic expression for the Wilson coefficient $C_1$ and demonstrates that the quartic scalar interaction must be included at NNLO, revealing a two-scale renormalization structure. Through renormalization-group analysis, it constrains the scalar couplings and performs a detailed phenomenological study for the Tevatron and LHC, showing potentially large deviations from the SM cross section. The results indicate that Tevatron Higgs-exclusion limits could stringently constrain the color-octet parameter space, competitive with direct searches, and point to extensions to more complex scalar sectors in future work.

Abstract

We compute the next-to-next-to-leading order QCD corrections to the gluon-fusion production of a Higgs boson in models with massive color-octet scalars in the ${\bf (8,1)_0}$ representation using an effective-theory approach. We derive a compact analytic expression for the relevant Wilson coefficient, and explain an interesting technical aspect of the calculation that requires inclusion of the quartic-scalar interactions at next-to-next-to-leading order. We perform a renormalization-group analysis of the scalar couplings to derive the allowed regions of parameter space, and present phenomenological results for both the Tevatron and the LHC. The modifications of the Higgs production cross section are large at both colliders, and can increase the Standard Model rate by more than a factor of two in allowed regions of parameter space. We estimate that stringent constraints on the color-octet scalar parameters can be obtained using the Tevatron exclusion limit on Higgs production.

Figures (6)

• Figure 1: Example of a three-loop diagram necessitating the inclusion of the quartic-scalar term in the Lagrangian.
• Figure 2: Example two-scale diagrams contributing to the Wilson coefficient at NNLO.
• Figure 3: Maximum value of $\lambda_1$ allowed by perturbativity for the choices $G_{4S}(v)=1$ and $G_{4S}(v)=0$, as a function of Higgs mass.
• Figure 4: Higgs production cross section in gluon-fusion at the LHC for $m_S=300$ GeV as a function of the Higgs boson mass. The bands indicate the scale variation $m_h/4 \leq \mu \leq m_h$. From bottom to top, the bands indicate the variations of the LO, NLO, and NNLO cross sections. All other parameters are as described in the text. For orientation, the SM result at NNLO for the central value $\mu=m_h /2$ is shown.
• Figure 5: Higgs production cross section in gluon-fusion at the Tevatron for $m_h=165$ GeV as a function of the scalar mass. The bands indicate the scale variation $m_h/4 \leq \mu \leq m_h$. All other parameters are as described in the text. Also shown is the SM cross section with its corresponding scale uncertainty.