[Paper Review] Unveiling the MSSM Neutral Higgs Bosons with Leptons and a Bottom Quark

Bariş Altunkaynak, Chung Kao+1 more|arXiv (Cornell University)|Dec 11, 2013

Particle physics theoretical and experimental studies3 citations

TL;DR

This paper investigates the discovery potential of neutral Higgs bosons in the Minimal Supersymmetric Standard Model (MSSM) via associated production with a bottom quark, followed by decay into tau leptons that further decay into electron-muon pairs ($bg \to b\phi^0 \to b\tau^+\tau^- \to be^\pm\mu^\mp + \not{E}_T$). With $\sqrt{s} = 14$ TeV and $L = 300$ fb$^{-1}$, the $5\sigma$ discovery reach extends to $M_A \approx 800$ GeV for $\tan\beta \approx 50$, and beyond 1 TeV for $\tan\beta \approx 60$, leveraging cleaner topology and reduced jet-tagging uncertainties compared to $\tau$-jet channels.

ABSTRACT

We investigate the prospects for the discovery of neutral Higgs bosons produced with a bottom quark where the Higgs decays into a pair of tau leptons and the taus decay into an electron-muon pair, i.e. $bg o bϕ^0 o bτ^+τ^- o be^\pmμ^\mp + E\!\!\!/_T$, $ϕ^0 = h^0, H^0, A^0$. Our study has been done within the framework of the Minimal Supersymmetric Standard Model. We consider the dominant physics backgrounds including the production of Drell-Yan processes ($bτ^+τ^-$ and $jτ^+τ^-, j = q, g$), top quark pair ($t\bar{t}$), $tW$ and $jWW$ with realistic acceptance cuts and efficiencies. We present $5σ$ discovery contours for the neutral Higgs bosons in the ($M_A, anβ$) plane as well as the region with a favored light Higgs mass (123 GeV $\le m_h\le$ 129 GeV). Promising results are found for the CP-odd pseudoscalar ($A^0$) and the heavier CP-even scalar ($H^0$) Higgs bosons with masses up to 800 GeV and $ anβ\simeq 50$ at the LHC with a center of mass energy ($\sqrt{s}$) of 14 TeV and an integrated luminosity ($L$) of 300 fb$^{-1}$. With $\sqrt{s} =$ 14 TeV and $L =$ 3000 fb$^{-1}$, LHC will be able to discover the Higgs pseudoscalar and the heavier Higgs scalar beyond $M_A = 1000$ GeV.

Motivation & Objective

• To explore a clean, $\tau$-jet free signature for neutral MSSM Higgs bosons using final states with opposite-sign electron-muon pairs and missing transverse energy.
• To assess the discovery potential of $h^0$, $H^0$, and $A^0$ in the $bg \to b\phi^0 \to b\tau^+\tau^- \to be^\pm\mu^\mp + \not{E}_T$ channel at the LHC.
• To evaluate the impact of realistic acceptance cuts, detector efficiencies, and dominant backgrounds (Drell-Yan, $t\bar{t}$, $tW$, $jWW$) on signal observability.
• To determine $5\sigma$ discovery contours in the ($M_A$, $\tan\beta$) plane under various luminosity and energy conditions.
• To examine the reach for the MSSM Higgs sector under a heavy SUSY spectrum, consistent with current LHC exclusion limits.

Proposed method

• The signal process is $bg \to b\phi^0 \to b\tau^+\tau^- \to be^\pm\mu^\mp + \not{E}_T$, with $\phi^0 = h^0, H^0, A^0$, studied within the MSSM framework.
• Full spin correlations are included in the calculation of dominant backgrounds: Drell-Yan ($b\tau^+\tau^-$, $j\tau^+\tau^-$), $t\bar{t}$, $tW$, and $jWW$.
• Acceptance cuts and detector efficiencies are applied to simulate realistic LHC conditions, including $\hat{s}_{\text{min}}^{1/2}$ variable to enhance signal-to-background ratio.
• Signal and background cross sections are computed at parton level with $\sqrt{s} = 14$ TeV, and $5\sigma$ discovery contours are derived for integrated luminosities of 30, 300, and 3000 fb$^{-1}$.
• The analysis assumes a heavy SUSY spectrum ($M_{\text{SUSY}} = 1$ TeV) to reduce SUSY contributions to the signal, focusing on Higgs production and decay.

Experimental results

Research questions

• RQ1 What is the $5\sigma$ discovery reach for MSSM neutral Higgs bosons in the $be^\pm\mu^\mp + \not{E}_T$ final state at the LHC with $\sqrt{s} = 14$ TeV and $L = 300$ fb$^{-1}$?
• RQ2 How does the signal cross section and background suppression vary with $M_A$ and $\tan\beta$ in the $bg \to b\phi^0 \to b\tau^+\tau^- \to be^\pm\mu^\mp + \not{E}_T$ channel?
• RQ3 To what extent does the $\hat{s}_{\text{min}}^{1/2}$ cut improve the signal significance in high-mass regions?
• RQ4 How does the discovery potential compare across different Higgs states ($A^0$, $H^0$, $h^0$) and for varying luminosities?
• RQ5 What is the sensitivity of the $be^\pm\mu^\mp + \not{E}_T$ channel relative to $\tau$-jet-based channels, especially in terms of background suppression and reduced tagging uncertainties?

Key findings

• For $\sqrt{s} = 14$ TeV and $L = 300$ fb$^{-1}$, the $5\sigma$ discovery reach extends to $M_A \approx 800$ GeV for $\tan\beta \approx 50$, and to nearly $M_A = 1$ TeV for $\tan\beta \approx 60$.
• The signal cross section is approximately 1.5 fb for $M_A = 800$ GeV and $\tan\beta = 50$ at $\sqrt{s} = 14$ TeV.
• The Drell-Yan process is the dominant background at low $M_A$, while $t\bar{t}$ and $tW$ dominate at high $M_A$.
• The $\hat{s}_{\text{min}}^{1/2}$ cut significantly improves signal significance, especially in high-mass regions.
• The $be^\pm\mu^\mp + \not{E}_T$ channel offers a cleaner alternative to $\tau$-jet-based channels by eliminating uncertainties from $\tau$-jet tagging.
• With $L = 3000$ fb$^{-1}$, the LHC can probe $A^0$ and $H^0$ Higgs bosons beyond $M_A = 1000$ GeV for large $\tan\beta$.