The 7 TeV LHC Reach for MSSM Higgs Bosons

TL;DR

This study evaluates the 7 TeV LHC sensitivity to MSSM Higgs bosons, accounting for the altered Higgs spectrum and branching ratios due to doublet mixing. It assesses the reach across the $m_A$–$\tan\beta$ plane in two benchmark mixing scenarios (minimal and maximal) using a simplified combination of channels and the $R^{95}$ metric, and explores how Tevatron data and nonstandard Higgs searches complement LHC results. The analysis highlights how low $m_A$ can suppress standard $h\to\gamma\gamma,WW$ channels, increasing the importance of $h\to\tau\tau$, $Vh\to b\bar{b}$, and $H/A\to\tau\tau$ searches, while in regions like the small $\alpha_{eff}$ scenario, $h\to\gamma\gamma$ can be enhanced, enabling discovery with modest luminosity. Overall, the work demonstrates a path to near-complete MSSM coverage at 7 TeV through a combination of LHC channels, Tevatron data, and nonstandard Higgs searches, with implications for early discovery and parameter-space exclusion.

Abstract

The search for the Higgs boson is entering a decisive phase. The Large Hadron Collider experiments have collected more than 1 fb$^{-1}$ of data and are now capable of efficiently probing the high Higgs mass region, $m_H > 140$ GeV. The low mass region is more challenging at the LHC, but if the Higgs has Standard Model (SM)-like properties, the LHC should find evidence for it by the end of next year. In low energy supersymmetric extensions of the SM, the situation is similar for large values of the CP-odd Higgs mass $m_A$, but more interesting for lower values of $m_A$. The ($\sqrt{s}$ =7 TeV) LHC searches for a low-mass Standard Model Higgs boson predominantly in the $h\rightarrow γγ,WW$ decay modes, which may be suppressed by an increase in the $h\rightarrow b\bar{b}, τ^+ τ^-$ partial widths (and thus the total $h$ width) for $m_A\lesssim 500$ GeV. Although $h\rightarrow b\bar{b}, τ^+ τ^-$ are sought at the LHC, these channels are not powerful enough to fully counter this suppression in the first year of running. We consider two alternative possibilities for probing the low $m_A$ region: nonstandard Higgs boson searches at the LHC, and a statistical combination with the Tevatron, where $Vh\rightarrow b\bar{b}$ is the primary search channel for light $h$. We also study an MSSM scenario in which the $h\rightarrowγγ$ rate is enhanced at low $m_A$ to the point where discovery is possible in the near future.

Figures (8)

• Figure 1: Top row: Estimated median LHC reach for the light, SM-like Higgs boson in the minimal mixing (left) and maximal mixing (right) benchmark scenarios of the MSSM with 5 fb$^{-1}$/experiment. Middle (Bottom) row: same, with 10 (15) fb$^{-1}$/experiment.
• Figure 2: Rates for $gg\rightarrow h\rightarrow\gamma\gamma,WW$ (solid) and $gg\rightarrow H\rightarrow\gamma\gamma,WW$ (dashed) in the MSSM, relative to the rates in the SM for a Higgs of mass $m_h$ or $m_H$, respectively. Four different curves are shown for each particle, demonstrating the relatively model-independent nature of the suppression.
• Figure 3: Enhancement of the $h \to b b$ decay branching ratio (left panel) and enhancement of the $h \to \gamma\gamma$ decay branching ratio (right panel) in the small $\alpha$ scenario of the MSSM.
• Figure 4: LHC reach for the light, SM-like Higgs boson in the small $\alpha_{eff}$ benchmark scenario of the MSSM. Left: 5 fb$^{-1}$/experiment; Right: 10 fb$^{-1}$/experiment.
• Figure 5: Estimated median Tevatron reach for the light, SM-like Higgs boson in the minimal mixing (left) and maximal mixing (right) benchmark scenarios of the MSSM.