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Higgs Boson Discovery and Properties

J. F. Gunion, L. Poggioli, R. Van Kooten

TL;DR

The report analyzes how to discover a Standard Model-like Higgs and measure its fundamental properties using a suite of future colliders, presenting a framework that partitions Higgs masses into five regions and prescribes rate- and recoil-based methods to determine couplings, total width, partial widths, and CP characteristics. It demonstrates that precise, model-independent determinations of $m_{h}$, $(ZZh)^2$, $(WWh)^2$, $(ggh)^2$, BRs to $b\overline b$, $c\overline c$, and $WW^*$, as well as $\Gamma_{h}^{\rm tot}$, are feasible with planned data from LEP2, TeV33, LHC, NLC, and FMC, though accuracies depend strongly on detector performance and channel separations. The work also addresses non-minimal Higgs sectors (MSSM, NMSSM, 2HDM), showing potential no-lose regions and the need for complementary measurements to distinguish models; it highlights the role of unusual states like $A^0$, $H^0$, $H^{\pm}$ and $\Delta^{--}$, including their production and decay channels. Overall, the study argues for a comprehensive, multi-machine program (notably NLC and FMC in addition to LHC) to fully map Higgs properties, discriminate between SM-like and extended Higgs sectors, and guide high-scale model-building decisions.

Abstract

We outline issues examined and progress made by the Light Higgs Snowmass 1996 working group regarding discovering Higgs bosons and measuring their detailed properties. We focused primarily on what could be learned at LEP2, the Tevatron (after upgrade), the LHC, a next linear $\epem$ collider and a $\mupmum$ collider.

Higgs Boson Discovery and Properties

TL;DR

The report analyzes how to discover a Standard Model-like Higgs and measure its fundamental properties using a suite of future colliders, presenting a framework that partitions Higgs masses into five regions and prescribes rate- and recoil-based methods to determine couplings, total width, partial widths, and CP characteristics. It demonstrates that precise, model-independent determinations of , , , , BRs to , , and , as well as , are feasible with planned data from LEP2, TeV33, LHC, NLC, and FMC, though accuracies depend strongly on detector performance and channel separations. The work also addresses non-minimal Higgs sectors (MSSM, NMSSM, 2HDM), showing potential no-lose regions and the need for complementary measurements to distinguish models; it highlights the role of unusual states like , , and , including their production and decay channels. Overall, the study argues for a comprehensive, multi-machine program (notably NLC and FMC in addition to LHC) to fully map Higgs properties, discriminate between SM-like and extended Higgs sectors, and guide high-scale model-building decisions.

Abstract

We outline issues examined and progress made by the Light Higgs Snowmass 1996 working group regarding discovering Higgs bosons and measuring their detailed properties. We focused primarily on what could be learned at LEP2, the Tevatron (after upgrade), the LHC, a next linear collider and a collider.

Paper Structure

This paper contains 31 sections, 19 equations, 19 figures, 15 tables.

Table of Contents

  1. Introduction
  2. The SM or a SM-like Higgs boson
  3. Discovery of $h_{\rm SM}$ in the $Wh_{\rm SM}$ and $Zh_{\rm SM}$ modes at TeV33
  4. Strategies for verifying the properties of the $h_{\rm SM}$ using LEP2, TeV33 and LHC data only gp
  5. Enumeration of mass regions and reactions
  6. Using Observed Rates to Extract Higgs Couplings
  7. Measuring $\sigma BR(h_{\rm SM}\to c\overline c, b\overline b,WW^\star)$ using NLC and $s$-channel FMC data
  8. Measurements at $\sqrt s=500\,{\rm GeV}$
  9. Measuring $\sigma(\mu^+\mu^-\to h_{\rm SM})BR(h_{\rm SM}\to b\overline b,WW^\star,ZZ^\star)$ in $s$-channel FMC production
  10. Measuring $\sigma BR(h_{\rm SM}\to\gamma\gamma)$ at the NLC gm
  11. Determining the $ZZh_{\rm SM}$ coupling at the NLC
  12. Determining $h_{\rm SM}$ branching ratios and the $WWh_{\rm SM}$ coupling at the NLC
  13. $BR(h_{\rm SM}\to b\overline b)$ and $BR(h_{\rm SM}\to c\overline c)$
  14. $BR(h_{\rm SM}\to WW^\star)$
  15. $WWh_{\rm SM}$ coupling and testing custodial SU(2)
  16. ...and 16 more sections

Figures (19)

  • Figure 1: Total width versus mass of the SM and MSSM Higgs bosons for $m_t=175\,{\rm GeV}$. In the case of the MSSM, we have plotted results for $\tan\beta =2$ and 20, taking $m_{\widetilde{t}}=1\,{\rm TeV}$ and including two-loop/RGE-improved Higgs mass corrections and neglecting squark mixing; SUSY decay channels are assumed to be absent.
  • Figure 2: Constant value contours in $(m_{A^0},\tan\beta)$ parameter space for the ratios $[WW^\star/b\overline b]_{h^0}/[WW^\star/b\overline b]_{h_{\rm SM}}$ and $[c\overline c/b\overline b]_{h^0}/[c\overline c/b\overline b]_{h_{\rm SM}}$. We assume "maximal-mixing" in the squark sector and present results for the case of fixed $m_{h^0}=110\,{\rm GeV}$. The band extending out to large $m_{A^0}$ at $\tan\beta\sim 2$ is where $m_{h^0}=110\,{\rm GeV}$ is theoretically disallowed in the case of maximal mixing. For no mixing, see Ref. dpfreport, the vertical contours are essentially identical --- only the size of the disallowed band changes.
  • Figure 3: Purity vs. efficiency for $b$ and $c$ single jet tagging using the topological tagging techniques of Ref. rvdj.
  • Figure 4: Signal and background rates for $L=50~{\rm fb}^{-1}$ at $\sqrt s=500\,{\rm GeV}$ for $e^+e^-\to \nu\overline \nu WW^\star$ as a function of $WW^\star$ mass, taking $m_{h_{\rm SM}}=150\,{\rm GeV}$.
  • Figure 5: The fractional error in the measurement of $\sigma(\nu_e \bar{\nu}_e h_{\rm SM})BR(h_{\rm SM}\to\gamma\gamma)$ [$\sigma(Zh_{\rm SM})BR(h_{\rm SM}\to\gamma\gamma)$] as a function of $m_{h_{\rm SM}}$ assuming $L=200~{\rm fb}^{-1}$ is accumulated at $\sqrt s=500\,{\rm GeV}$ [$\sqrt s=\sqrt s_{\rm opt}$]. Also shown is the fractional $\sigma BR(h_{\rm SM}\to\gamma\gamma)$ error obtained by combining $Zh_{\rm SM}$ and $\nu_e\overline\nu_eh_{\rm SM}$ channels for $L=200~{\rm fb}^{-1}$ at $\sqrt s=500\,{\rm GeV}$. Results for the four electromagnetic calorimeter resolutions described in the text are given.
  • ...and 14 more figures