Higgs Boson Production via Gluon Fusion: Squark Loops at NLO QCD

TL;DR

This work addresses reliable predictions for MSSM Higgs production via gluon fusion by computing pure QCD NLO corrections to squark-loop contributions with full mass dependence, including related corrections to h/H → γγ and h/H → gg. The authors develop a renormalizable framework, employ running squark masses to improve perturbative behavior, and analyze a gluophobic scenario to illustrate interference effects. They find that NLO corrections can be large, with significant squark-mass effects near thresholds, and that scale uncertainties are substantially reduced at NLO, underscoring the importance of these corrections for LHC and photon-collider phenomenology. The results, implemented in the HIGLU tool, provide improved, mass-dependent predictions essential for accurate MSSM Higgs analyses across parameter spaces.

Abstract

The loop-induced processes gg -> h,H,A provide the dominant Higgs boson production mechanisms at the Tevatron and LHC in a large range of the minimal supersymmetric extension of the Standard Model. For squark masses below \sim 400 GeV squark loop contributions become important in addition to the top and bottom quark loops. The next-to-leading order QCD corrections to the squark contributions of these processes are determined including the full squark and Higgs mass dependences. They turn out to be large and thus important for the Tevatron and LHC experiments. Squark mass effects of the K factors can be of O(20%). In addition we derive the QCD corrections to the squark contributions of the rare photonic Higgs decays h,H -> gamma gamma, which play a role for the Higgs searches at the LHC.

Figures (16)

• Figure 1: MSSM Higgs boson production via gluon fusion mediated by top- and bottom quark as well as stop and sbottom loops at leading order.
• Figure 2: MSSM Higgs boson couplings to photon pairs mediated by top- and bottom quark, stop and sbottom as well as $W$ boson loops at leading order.
• Figure 3: Generic diagrams for the NLO QCD corrections to the squark contributions to the photonic Higgs couplings.
• Figure 4: Real and imaginary parts of the QCD correction factor to the squark amplitudes of the two-photon couplings for the scalar MSSM Higgs bosons. The renormalization scale of the running squark mass is taken to be $\mu=M_{\cal H}/2$.
• Figure 5: QCD corrected partial decay widths of the scalar MSSM Higgs bosons to two photons as functions of the corresponding Higgs masses for ${\rm tg}\beta=3$ and 30. The full curves include all loop contributions, in the dashed lines the squark contributions are omitted and in the dotted lines all SUSY particle loops are neglected. The kinks, bumps and spikes correspond to the $WW, \tilde{t}_1\bar{\tilde{t}}_1, t\bar{t}, \tilde{b}_1\bar{\tilde{b}}_1, \tilde{\tau}_1 \bar{\tilde{\tau}}_1, \tilde{\tau}_2 \bar{\tilde{\tau}}_2$ and $\tilde{b}_2\bar{\tilde{b}}_2$ thresholds in consecutive order with rising Higgs mass. The renormalization scale of the running quark and squark masses is chosen to be $M_{h/H}/2$, while the scale of $\alpha_s$ is taken to be the corresponding Higgs mass.