Discovering the Higgs with Low Mass Muon Pairs

TL;DR

This work addresses non-minimal electroweak symmetry breaking models that harbor a light pseudoscalar $a^0$, which can dramatically alter Higgs decays. It proposes a collider strategy exploiting the subdominant $a^0 o oldsymbol{}oldsymbol{}$ mode in $h^0 o a^0 a^0$, yielding a $2oldsymbol{}2 au$ final state and a measurable signal despite small branching fractions, parameterized by $oldsymbol{}_{ au} = 2 ext{Br}(a^0 o oldsymbol{}oldsymbol{}) ext{Br}(a^0 o au^+ au^-)$. The analysis combines signal generation (PYTHIA), detector effects, and realistic backgrounds (Drell–Yan, WW, $tar t$, etc.) to project sensitivities at the Tevatron and LHC, showing that with existing data the Tevatron can probe Higgs masses near 102–110 GeV and the LHC can achieve discovery with early luminosity. These results provide a concrete path to test NMSSM-like scenarios and to probe the symmetry structure of the Higgs potential via nonstandard decay modes.

Abstract

Many models of electroweak symmetry breaking have an additional light pseudoscalar. If the Higgs boson can decay to a new pseudoscalar, LEP searches for the Higgs can be significantly altered and the Higgs can be as light as 86 GeV. Discovering the Higgs boson in these models is challenging when the pseudoscalar is lighter than 10 GeV because it decays dominantly into tau leptons. In this paper, we discuss discovering the Higgs in a subdominant decay mode where one of the pseudoscalars decays to a pair of muons. This search allows for potential discovery of a cascade-decaying Higgs boson with the complete Tevatron data set or early data at the LHC.

Figures (7)

• Figure 1: The branching fraction of the Higgs into pseudoscalars as a function of $\langle S\rangle/\sin 2\beta$ for $m_{h^0}=100\text{ GeV}$ when $\tilde{d}_h=0$ and $1$ (solid and dashed lines, respectively). The inset shows the minimum value of the branching rate into the Standard Model as a function of $m_{h^0}$.
• Figure 2: Values of $\langle S \rangle/\sin2\beta$ (GeV) that have been excluded through LEP2's search for a Standard Model Higgs Barate:2003sz. The region below $m_{h^0} =86$ GeV is entirely excluded by the $h^0 \rightarrow 4 \tau$ search Abbiendi:2002in.
• Figure 3: Region of $m_{a^0} - g_d$ parameter space that has been excluded by CLEO to 90% C.L :2008hs. The dashed lines indicate values of $\langle S \rangle /\sin 2\beta$ for $\tan\beta = 2$. The shaded region shows the minimum values of $g_d$ allowed by LEP for an 87-110 GeV Higgs.
• Figure 4: Schematic of Higgs decay chain. The muons and taus will be highly boosted and nearly collinear. It is likely that the taus will be reconstructed as one jet. Most of the $\hbox{$E_T\space\not\space$}$ in the event will be in the direction of this jet.
• Figure 5: Muon invariant mass for 5 fb$^{-1}$ at the LHC before (inset) and after the $p_T^{\mu\mu}$, $\hbox{$E_T\space\not\space$}$, and $\Delta R$ cuts. The signal, a 100 GeV Higgs decaying to a pair of 7 GeV pseudoscalars, is shown in black and the Drell-Yan background is shown in gray.