Buried Higgs

Abstract

We present an extension of the MSSM where the dominant decay channel of the Higgs boson is a cascade decay into a four-gluon final state. In this model the Higgs is a pseudo-Goldstone boson of a broken global symmetry SU(3)-> SU(2). Both the global symmetry breaking and electroweak symmetry breaking are radiatively induced. The global symmetry breaking pattern also implies the existence of a light (few GeV) pseudo-Goldstone boson eta which is a singlet under the standard model gauge group. The h -> eta eta branching fraction is large, and typically dominates over the standard h -> b b decay. The dominant decay of eta is into two gluons, while the decays to photons, taus or lighter standard model flavors are suppressed at the level of 10^(-4) or more. With h-> 4 jets as the dominant decay, the Higgs could be as light as 78 GeV without being detected at LEP, while detection at the LHC is extremely challenging. However many of the super- and global symmetry partners of the standard model particles should be easily observable at the LHC. Furthermore, the LHC should be able to observe a "wrong Higgs" that is a 300-400 GeV heavy Higgs-like particle with suppressed couplings to W and Z that by itself does not account for electroweak precision observables and the unitarity of WW scattering. At the same time, the true Higgs is deeply buried in the QCD background.

Figures (7)

• Figure 1: The parameter $\xi^2 {\mathrm{BR}}(h \to b \overline b)$ in this model for 3 representative values of the global symmetry breaking scale as a function of the Higgs mass. The dashed line is an approximation of the observed LEP bound transcribed from the actual LEP plot reprinted from LEP4b on the right hand side. We can see that while for $f=450$ GeV the bound is over 110 GeV for the Higgs mass, for $f=350$ GeV the Higgs could be lighter than 90 GeV.
• Figure 2: The mass of the pGB Higgs (left panel) and the radial mode (right panel) for a sample slice of the parameter space, for $f = 350$ (dahshed blue) and $f = 400$ (solid red) GeV. This plot was obtained using the full 1-loop Coleman-Weinberg potential including the mixing between the Higgs and the radial mode.
• Figure 3: A scan of the parameter space for the achievable $\eta$ and Higgs masses. In the left panel we show the Higgs mass with $\tilde{y}_{b1,b2}=0$, and see that for the interesting range of Higgs masses $m_{\eta}<3$ GeV. In the right we varied $0.001 <\tilde{y}_{b1} < 0.002$. We can see that with this non-collective Yukawa one can easily get $m_{\eta}$ in the 5--10 GeV range. We have fixed $f=350, F= \sqrt{2} \cdot 10^4, \Lambda=10^7$ GeV for both plots, and scanned the remaining parameters in the regions $0.02<y_1<0.3, 1<y_2<2.4, 0.02<y_{b1}<0.12$ and $300<M_{soft}<1000$ GeV.
• Figure 4: On the left the contours of the Higgs mass (dashed red line) and the $\eta$ mass (solid black lines) as function of the universal soft breaking mass $M_{soft}$ and the top Yukawa $y_2$. On the right, the necessary fine tunings $FT_3$ (solid black) and $FT_2$ (dashed red) in percent. The kink in the contour lines at $y_2\approx 1.64$ appears because the cut-off for larger values is determined by the Landau pole of $y_2$. These plots are based on the full numerical 1-loop Coleman-Weinberg potential, with $f=350$ GeV, $y_1= 0.29, y_{b1} = 0.1, y_{b2} = 0, \tilde{y}_{b1} = 0.001, \tan\beta = 10, F = \sqrt{2}\cdot 10^4$ and $\tilde{y}_{b2}= 0$. The region in the lower left is excluded by the LEP $\xi^2 {\mathrm{BR}}(h \to b \overline b)$ bound and in the lower right because $m_{\eta}>2 m_b$.
• Figure 5: The same as in \ref{['f.350GeV']} for $f=400$ GeV.