The meaning of “Higgs”: ${\tau }^{+}{\tau }^{-}$ and $\gamma \gamma$ at the Fermilab Tevatron and the CERN LHC

In this paper we discuss how to extract information about physics beyond the standard model (SM) from searches for a light SM Higgs boson at Tevatron Run II and CERN LHC. We demonstrate that new (pseudo)scalar states predicted in both supersymmetric and dynamical models can have enhanced visibility in standard Higgs search channels, making them potentially discoverable at Tevatron Run II and CERN LHC. We discuss the likely sizes of the enhancements in the various search channels for each model and identify the model features having the largest influence on the degree of enhancement. We compare the key signals for the nonstandard scalars across models and also with expectations in the SM, to show how one could start to identify which state has actually been found. In particular, we suggest the likely mass reach of the Higgs search in $p\overline{p}/pp\to \mathcal{H}\to {\tau }^{+}{\tau }^{-}$ for each kind of nonstandard scalar state and we demonstrate that $p\overline{p}/pp\to \mathcal{H}\to \gamma \gamma$ may cleanly distinguish the scalars of supersymmetric models from those of dynamical models.

Figure 1

Left frame: Higgs spectrum in the MSSM. Lower curves indicate $M_h$ vs $M_A$ for indicated values of $\tan \beta$. Upper curves do likewise for $M_H$ vs $M_A$. Note the potential for degenerate Higgs masses near 120 GeV. Right frame: Branching ratios of the dominant decay modes of the SM Higgs boson. Results have been obtained with the program HDECAY [15] for ${\alpha }_s(M_Z^2)=0.120$, ${\overline{m}}_b(m_b)=4.22\mathrm{GeV}$, $m_t=178\mathrm{GeV}$.

Figure 2

Branching ratios of the dominant decay modes of the MSSM $CP$-odd Higgs boson. Results have been obtained with the program HDECAY [15] for ${\alpha }_s(M_Z^2)=0.120$, ${\overline{m}}_b(m_b)=4.22\mathrm{GeV}$, $m_t=178\mathrm{GeV}$. Frames (a), (b), (c), and (d) correspond to $\tan \beta =5$, 10, 30, and 50, respectively.

Figure 3

Branching ratios of the dominant decay modes of the MSSM light Higgs boson. Results have been obtained with the program HDECAY [15] for ${\alpha }_s(M_Z^2)=0.120$, ${\overline{m}}_b(m_b)=4.22\mathrm{GeV}$, $m_t=178\mathrm{GeV}$. Frames (a), (b), (c), and (d) correspond to $\tan \beta =5$, 10, 30, and 50, respectively.

Figure 4

Branching ratios of the dominant decay modes of the MSSM heavy Higgs boson. Results have been obtained with the program HDECAY [15] for ${\alpha }_s(M_Z^2)=0.120$, ${\overline{m}}_b(m_b)=4.22\mathrm{GeV}$, $m_t=178\mathrm{GeV}$. Frames (a), (b), (c), and (d) correspond to $\tan \beta =5$, 10, 30, and 50, respectively.

Figure 5

NLO cross sections for Higgs production via the $b\overline{b}\to \mathcal{H}$ and $gg\to \mathcal{H}$ processes (as well as their sum) for (a) the SM Higgs, and (b)–(d) the supersymmetric axial Higgs boson with $\tan \beta =10$, 30, and 50, respectively, at the Tevatron.

Figure 6

NLO cross sections for Higgs production via the $b\overline{b}\to \mathcal{H}$ and $gg\to \mathcal{H}$ processes (as well as their sum) for (a) the SM Higgs, and (b)–(d) the supersymmetric axial Higgs boson with $\tan \beta =10$, 30, and 50, respectively, at the LHC.

Figure 7

Enhancement factor ${\kappa }_{\mathrm{tot}/xx}^{\mathcal{H}}$ for final states $xx=b\overline{b},{\tau }^{+}{\tau }^{-},WW,ZZ,\gamma \gamma$ when both $gg\to \mathcal{H}$ and $b\overline{b}\to \mathcal{H}$ are included and the signals of all three MSSM Higgs states are combined. Frames (a), (b), (c), and (d) correspond to $\tan \beta =5$, 10, 30, and 50, respectively, at the Tevatron (solid lines) and at the LHC (dashed lines).

Figure 8

Enhancement factor ${\kappa }_{bb/\tau \tau }^{\mathcal{H}}$ (for $b\overline{b}\to H+h+A\to {\tau }^{+}{\tau }^{-}$) for the minimal (left) and maximal (right) mixing scenarios. In both scenarios ${\kappa }_{bb/\tau \tau }^{\mathcal{H}}$ is the same (within at most a few percent) for fixed $M_A$, $\mu$ and $M_{\mathrm{SUSY}}$ parameters: ${\kappa }_{bb/\tau \tau }^{\mathcal{H}}$ is independent of the collider energy and essentially independent of the $X_t$ variable which describes top squark mixing.

Figure 9

Results for $gg+b\overline{b}\to h+H+A\to {\tau }^{+}{\tau }^{-}$ at Tevatron Run II. Left frame: Selected contours of given enhancement factor values ${\kappa }_{\mathrm{total}/\tau \tau }^{\mathcal{H}}$ in the MSSM. Right frame: Predicted Tevatron reach, based on the $h_{SM}\to {\tau }^{+}{\tau }^{-}$ studies of [9], in the MSSM parameter space. Lower contour is a $2\sigma$ exclusion contour; upper contour is a $5\sigma$ discovery contour.

Figure 10

Results for $gg+b\overline{b}\to h+H+A\to {\tau }^{+}{\tau }^{-}$ at LHC. Left frame: Selected contours of given enhancement factor values ${\kappa }_{\mathrm{total}/\tau \tau }^{\mathcal{H}}$ in the MSSM. Right frame: Predicted LHC reach, based on the $h_{SM}\to {\tau }^{+}{\tau }^{-}$ studies of 10, in the MSSM parameter space.

Figure 11

Total enhancement factor for each technicolor model as a function of technipion mass and assuming the final state is a tau pair (left frame) or photon pair (right frame). The $5\sigma$ discovery and $2\sigma$ exclusion curves indicate the required enhancement factor for a Higgs-like particle at Tevatron Run II when the final state is ${\tau }^{+}{\tau }^{-}$ [9] (left frame) or $\gamma \gamma$ [11] (right frame).

Figure 12

$\sigma \times Br$ for each technicolor model plotted as a function of technipion mass and assuming the final state is a tau ($\gamma$) pair—left (right) at LHC. The lowest curve is the $\sigma \times Br$ required to make a Higgs-like particle visible ($5\sigma$ discovery) in ${\tau }^{+}{\tau }^{-}$ [10] or in $\gamma \gamma$ [12] at LHC.