The 7 TeV LHC reach for MSSM Higgs bosons

The search for the Higgs boson is entering a decisive phase. The Large Hadron Collider experiments have collected more than $1{\mathrm{fb}}^{-1}$ of data and are now capable of efficiently probing the high Higgs mass region, $m_H>140\mathrm{GeV}$. The low mass region is more challenging at the LHC, but if the Higgs has standard model-like properties, the LHC should find evidence for it by the end of next year. In low energy supersymmetric extensions of the standard model, 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 ($\sqrt{s}=7\mathrm{TeV}$) LHC searches for a low mass standard model Higgs boson predominantly in the $h\to \gamma \gamma$, $WW$ decay modes, which may be suppressed by an increase in the $h\to b\overline{b}$, ${\tau }^{+}{\tau }^{-}$ partial widths (and thus the total $h$ width) for $m_A\lesssim 500\mathrm{GeV}$. Although $h\to b\overline{b}$, ${\tau }^{+}{\tau }^{-}$ 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 $Vh\to b\overline{b}$ is the primary search channel for light $h$. We also study a minimal supersymmetric standard model scenario in which the $h\to \gamma \gamma$ rate is enhanced at low $m_A$ to the point where discovery is possible in the near future.

Figure 1

Top row: Estimated median LHC reach for the light, SM-like Higgs boson in the minimal mixing (left panel) and maximal mixing (right panel) benchmark scenarios of the MSSM with $5{\mathrm{fb}}^{-1}/\mathrm{\text{experiment}}$. Middle (bottom) row: The same as the top row, with $10(15){\mathrm{fb}}^{-1}/\mathrm{\text{experiment}}$.

Figure 2

Rates for $gg\to h\to \gamma \gamma$, $WW$ (solid line) and $gg\to H\to \gamma \gamma$, $WW$ (dashed line) 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

Estimated median LHC reach for the light, SM-like Higgs boson in the minimal mixing (left panel) and maximal mixing (right panel) benchmark scenarios of the MSSM with $5{\mathrm{fb}}^{-1}/\mathrm{\text{experiment}}$ and an increase in the standard benchmark value of $\mu$ from 200 GeV (as in Fig. 1) to 500 GeV.

Figure 4

Enhancement of the $h\to bb$ 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 5

LHC reach for the light, SM-like Higgs boson in the small ${\alpha }_{\mathrm{eff}}$ benchmark scenario of the MSSM. Left panel: $5{\mathrm{fb}}^{-1}/\mathrm{\text{experiment}}$; right panel: $10{\mathrm{fb}}^{-1}/\mathrm{\text{experiment}}$.

Figure 6

Estimated median Tevatron reach for the light, SM-like Higgs boson in the minimal mixing (left panel) and maximal mixing (right panel) benchmark scenarios of the MSSM.

Figure 7

Estimated median combined Tevatron+LHC reach for the light, SM-like Higgs boson in the minimal mixing (left panels) and maximal mixing (right panels) benchmark scenarios of the MSSM. Top panels: $5{\mathrm{fb}}^{-1}/\mathrm{\text{experiment}}$ for the LHC, $10{\mathrm{fb}}^{-1}/\mathrm{\text{experiment}}$ for the Tevatron. Bottom panels: $10{\mathrm{fb}}^{-1}/\mathrm{\text{experiment}}$ for both the Tevatron and the LHC.

Figure 8

LHC reach for the light, SM-like Higgs boson and the nonstandard Higgs states in the minimal mixing (left panel) and maximal mixing (right panel) benchmark scenarios of the MSSM.

Figure 9

Same as Fig. 5, but with nonstandard searches overlaid, showing both the current limits from $H/A\to \tau \tau$ (dashed curve) and the projected reach with $5{\mathrm{fb}}^{-1}$ (shaded region).