Hadronic Higgs Production and Decay in Supersymmetry at Next-to-Leading Order

TL;DR

The paper addresses the NLO SUSY QCD corrections to CP-even Higgs production and decay via gluon coupling in the MSSM, demonstrating that a consistent treatment requires including gluino effects. It constructs an effective gluon-Higgs Lagrangian by integrating out the heavy states and computes the NLO coefficient $C_1$ using asymptotic expansions across mass hierarchies, then applies standard five-flavor QCD to obtain decay widths and hadronic cross sections. The results show that SUSY corrections modify the NLO K-factor by at most about $5\%$, typically reducing the QCD contribution, and that previous squark-only analyses were incomplete due to uncanceled ultraviolet terms involving gluinos. The findings confirm that MSSM SUSY QCD effects on Higgs production at the LHC are small in the examined parameter space, while also underscoring the necessity of including gluino contributions for a consistent framework and paving the way for studies with general squark mixing.

Abstract

Supersymmetric QCD corrections to the gluonic production and decay rate of a CP-even Higgs boson are evaluated at next-to-leading order. To this aim, we derive an effective Lagrangian for the gluon-Higgs coupling. We show that a consistent calculation requires the inclusion of gluino effects, in contrast to what has been done previously. The supersymmetric corrections to the gluon-Higgs coupling lead to a modification of the next-to-leading order K-factor for the Higgs production rate at the LHC by less than five percent.

Figures (5)

• Figure 1: One-loop Feynman diagrams contributing to gluon fusion in the MSSM.
• Figure 2: Sample two-loop Feynman diagrams contributing to gluon fusion in the MSSM. Apart from the pure QCD corrections to the top quark $(a)$ and top squark $(b)$ triangle, there are also corrections involving the gluino $(c)$, $(d)$.
• Figure 3: $c^{\rm SUSY}$ for Case $(A)$ of Eq. (\ref{['eq::cases']}) with $(a)$$\tilde{M}_{t}{} = M_t{}$ and $(b)$$\tilde{M}_{t}{} = 2M_t{}$, as a function of the ratio $\tilde{M}_{t}{}/\tilde{M}_{g}{}$. The individual lines correspond to different orders of the expansion in the square of this ratio. The dotted line includes only the leading term, whereas the solid line incorporates corrections up to order $(\tilde{M}_{t}/\tilde{M}_{g})^{12}$.
• Figure 4: The quantity $2c^{\rm SUSY}$ as a function of the squark mass for $\tilde{M}_{g}=1$ TeV and $M_t=175$ GeV. Notice that the SUSY effects are negative.
• Figure 5: K-factors at NLO for Higgs production in gluon fusion in the Standard Model (dotted) and in Supersymmetry. Dashed line: $\tilde{M}_{R} = \tilde{M}_{L} = M_t = 175$ GeV, $\tilde{M}_{g} = 1$ TeV --- Solid line: $\tilde{M}_{R} = 1$ TeV, $\tilde{M}_{L} = M_t = 175$ GeV, $\tilde{M}_{g} = 400$ GeV. The bottom Yukawa coupling has been neglected. We use the LO and NLO parton densities of MRST2001Martin:2001es.