[Paper Review] Scope of Higgs production in association with a bottom quark pair in probing the Higgs sector of the NMSSM at the LHC

M. M. Almarashi, Stefano Moretti|arXiv (Cornell University)|May 8, 2012

Particle physics theoretical and experimental studies7 citations

TL;DR

This paper investigates the LHC's potential to detect a very light CP-odd Higgs boson $a_1$ in the NMSSM via associated production with a bottom quark pair at large $\tan\beta$. It identifies the $\tau^+\tau^-$ and $\mu^+\mu^-$ decay modes as optimal discovery channels, demonstrating that such light $a_1$ states—unavailable in the MSSM—are detectable and provide strong evidence for a non-minimal Higgs sector beyond the MSSM.

ABSTRACT

We review the potential of the LHC to detect a very light CP-odd Higgs boson of the NMSSM, $a_1$, through its direct production in association with a bottom-quark pair at large tan$β$. We also review the LHC discovery potential of the two lightest CP-even Higgs states, decaying into two lighter Higgs states or into the lightest CP-odd Higgs state and the $Z$ gauge boson.

Motivation & Objective

• To assess the LHC's discovery potential for a very light CP-odd Higgs boson $a_1$ in the NMSSM.
• To explore whether associated production with a bottom quark pair enables detection of $a_1$ at large $\tan\beta$, overcoming limitations of the MSSM.
• To evaluate the viability of $a_1$ discovery through $\tau^+\tau^-$, $\mu^+\mu^-$, and $\gamma\gamma$ decay modes despite large QCD backgrounds.
• To investigate the role of Higgs-to-Higgs decays in enhancing signal rates and enabling simultaneous detection of multiple Higgs states.
• To test the 'No-lose' and 'More-to-gain' theorems in the context of NMSSM Higgs phenomenology at the LHC.

Proposed method

• Analyzes the NMSSM Higgs sector with three CP-even, two CP-odd, and charged Higgs states arising from two doublets and a singlet superfield.
• Uses the NMSSM superpotential with $\lambda$ and $\kappa$ couplings to generate an effective $\mu$-term and break $U(1)_{PQ}$ symmetry, avoiding axion and domain wall problems.
• Constructs the scalar potential including F-terms, D-terms, and soft-breaking terms, with vacuum expectation values for $H_u$, $H_d$, and $S$.
• Performs a phenomenological analysis of Higgs production in association with $b\bar{b}$ pairs at the LHC, focusing on large $\tan\beta$ regime.
• Evaluates signal-to-background ratios for $a_1$ decays into $\tau^+\tau^-$, $\mu^+\mu^-$, $b\bar{b}$, and $\gamma\gamma$, using dominant backgrounds and kinematic cuts.
• Considers Higgs-to-Higgs decays such as $h_1 \to a_1 a_1$, $h_2 \to a_1 a_1$, and $h_2 \to h_1 h_1$, which are kinematically allowed in the NMSSM but not in the MSSM.

Experimental results

Research questions

• RQ1 Can the LHC detect a very light CP-odd Higgs boson $a_1$ with $m_{a_1} \lesssim M_Z$ via associated production with a bottom quark pair at large $\tan\beta$?
• RQ2 Which decay modes of $a_1$ offer the highest signal-to-background ratio for discovery at the LHC?
• RQ3 To what extent do Higgs-to-Higgs decays in the NMSSM enhance the discovery potential of multiple Higgs states simultaneously?
• RQ4 Is the $\gamma\gamma$ decay mode of $a_1$ viable for discovery despite large QCD backgrounds?
• RQ5 Can the LHC simultaneously detect $h_1$, $h_2$, and $a_1$ through associated production and cascade decays?

Key findings

• The $b\bar{b}$ associated production mode dominates at large $\tan\beta$ and provides the most favorable production channel for detecting a very light $a_1$.
• The $\tau^+\tau^-$ decay mode allows discovery of $a_1$ with mass up to $M_Z$, offering a clean signature with manageable backgrounds.
• The $\mu^+\mu^-$ decay mode enables detection of $a_1$ in the mass range $10 \lesssim m_{a_1} \lesssim 60$ GeV, where signal-to-background ratios are favorable.
• The $b\bar{b}$ decay mode, though dominant in branching fraction, is unviable for discovery due to overwhelming QCD backgrounds and poor signal-to-background ratios.
• The $\gamma\gamma$ decay mode, despite being dominant in some parameter regions, fails as a discovery channel due to insufficient signal significance.
• Higgs-to-Higgs decays such as $h_1 \to a_1 a_1$ and $h_2 \to a_1 a_1$ are dominant in sizable regions of the NMSSM parameter space, enabling the simultaneous detection of multiple Higgs states and supporting the 'More-to-gain' theorem.