Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

What is the W b anti-b, Z b anti-b or t anti-t b anti-b irreducible background to the light Higgs boson searches at LHC?

Borut Paul Kersevan, Elzbieta Richter-Was

TL;DR

The study addresses irreducible backgrounds to light Higgs searches in associated production channels at the LHC, focusing on Wbb, Zbb, and ttbb final states. It compares two Monte Carlo strategies: (a) complete massive 2→4 matrix elements via AcerMC plus PYTHIA shower, and (b) inclusive W/Z/tt production with PYTHIA parton shower, to evaluate background predictions under ATLAS-like selections. Key findings show channel-dependent discrepancies: Wbb PS yields higher rates and bb-topologies not always captured by ME; Zbb PS underestimates hard p_T tails due to multidiagram contributions; ttbb includes a non-negligible EW component that ME captures but PS does not, impacting Higgs observability in ttH. The authors emphasize that combining ME and PS approaches, along with pursuing NLO calculations, provides a more reliable background modeling framework for Higgs searches at the LHC, informing detector-level analyses and uncertainties.

Abstract

The W b anti-b, Z b anti-b and t anti-t b anti-b production at LHC are irreducible backgrounds for possible observability of the Standard Model (SM) and Minimal Supersymmetric Standard Model (MSSM) light Higgs boson respectively in the associated WH, ZH and t anti-t H production followed by the H -> b anti-b decay. We present a comparison of the background estimates as obtained with (a) complete massive matrix element implemented in AcerMC Monte Carlo generator and (b) PYTHIA implementation of the inclusive W, Z, and t anti-t production, followed by the parton showering mechanism. Both approaches lead to a production of the final state of interest, but differ in the approximations used. We concentrate on the comparison of these approaches for the background to the light Higgs boson searches at LHC.

What is the W b anti-b, Z b anti-b or t anti-t b anti-b irreducible background to the light Higgs boson searches at LHC?

TL;DR

The study addresses irreducible backgrounds to light Higgs searches in associated production channels at the LHC, focusing on Wbb, Zbb, and ttbb final states. It compares two Monte Carlo strategies: (a) complete massive 2→4 matrix elements via AcerMC plus PYTHIA shower, and (b) inclusive W/Z/tt production with PYTHIA parton shower, to evaluate background predictions under ATLAS-like selections. Key findings show channel-dependent discrepancies: Wbb PS yields higher rates and bb-topologies not always captured by ME; Zbb PS underestimates hard p_T tails due to multidiagram contributions; ttbb includes a non-negligible EW component that ME captures but PS does not, impacting Higgs observability in ttH. The authors emphasize that combining ME and PS approaches, along with pursuing NLO calculations, provides a more reliable background modeling framework for Higgs searches at the LHC, informing detector-level analyses and uncertainties.

Abstract

The W b anti-b, Z b anti-b and t anti-t b anti-b production at LHC are irreducible backgrounds for possible observability of the Standard Model (SM) and Minimal Supersymmetric Standard Model (MSSM) light Higgs boson respectively in the associated WH, ZH and t anti-t H production followed by the H -> b anti-b decay. We present a comparison of the background estimates as obtained with (a) complete massive matrix element implemented in AcerMC Monte Carlo generator and (b) PYTHIA implementation of the inclusive W, Z, and t anti-t production, followed by the parton showering mechanism. Both approaches lead to a production of the final state of interest, but differ in the approximations used. We concentrate on the comparison of these approaches for the background to the light Higgs boson searches at LHC.

Paper Structure

This paper contains 5 sections, 12 figures, 3 tables.

Table of Contents

  1. Introduction
  2. The $\mathbf{Wb \bar{b}}$ irreducible background
  3. The $\mathbf{Z b \bar{b}}$ irreducible background
  4. The $\mathbf{t \bar{t} b \bar{b}}$ irreducible background
  5. Conclusions

Figures (12)

  • Figure 1: The transverse momenta of the W-boson. Solid line denotes the PS events, dashed the ME events. Events were filtered as specified in the figure.
  • Figure 2: Top: the cone separation between b-jets, transverse momenta of the individual b-jets; Bottom: transverse momenta of the b-jet system and the invariant mass distribution of the b-jet system. Solid line denotes the PS events, the dashed one ME events.
  • Figure 3: The invariant mass distribution after gradually adding selection requirements is shown. Solid line denotes the PS events, the dashed one the ME events.
  • Figure 4: The transverse momenta of the Z-boson. Solid line denotes the PS events, dashed one the ME events. Events were filtered as specified in the figure.
  • Figure 5: Distributions of events with two tagged b-jets and a lepton pair with invariant mass around the mass of the Z-boson: The cone separation between b-jets, transverse momenta of individual b-jets, and transverse momenta of the b-jet system. Solid line denotes the ME events, the dashed one the PS events.
  • ...and 7 more figures