The Need for New Search Strategies for Fourth Generation Quarks at the LHC

Abstract

Most limits on the fourth generation heavy top quark (the t') are based on the assumed dominance of t' -> Wb, which is expected to be case in the minimal fourth generation framework with a single Higgs (the so called SM4). Here we show, within a variant of a Two Higgs Doublet Model with four generations of fermions, that, in general, a different t' detection strategy is required if the physics that underlies the new heavy fermionic degrees of freedom goes beyond the "naive" SM4. We find that the recent CMS lower bounds: m_{t'}< 450 GeV in the semi-leptonic channel pp -> t't' -> lνqqbb and m_{t'}< 557 GeV in the dilepton channel pp -> t't' ->llννbb, that were obtained using the customary (SM4-driven) detection strategies, do not apply. In particular, we demonstrate that if the decay t' -> ht dominates, then applying the "standard" CMS search tools leads to a considerably relaxed lower bound: m_{t'} >~350 GeV. We, therefore, suggest an alternative search strategy that is more sensitive to beyond SM4 dynamics of the fourth generation fermions.

12 pages, 8 figures

References in corpus (21)

• PYTHIA 6.4 Physics and Manual
• Combined search for the Standard Model Higgs boson using up to 4.9 fb-1 of pp collision data at sqrt(s) = 7 TeV with the ATLAS detector at the LHC
• Anatomy of New Physics in B-Bbar mixing
• Possible Indications of New Physics in Bd-mixing and in sin(2 beta) Determinations
• Less space for a new family of fermions
• Possible evidence for the breakdown of the CKM-paradigm of CP-violation
• The discovery of the fourth family at the LHC: what if?
• Patterns of Flavour Violation in the Presence of a Fourth Generation of Quarks and Leptons
• Four Generations, the Electroweak Phase Transition, and Supersymmetry
• LHC Signatures of Two-Higgs-Doublets with Fourth Family
• Source of CP Violation for the Baryon Asymmetry of the Universe
• Electroweak Symmetry Breaking from a Holographic Fourth Generation
• Constraints on the Four-Generation Quark Mixing Matrix from a Fit to Flavor-Physics Data
• Source of CP Violation for Baryon Asymmetry of the Universe
• Hints for the scale of new CP-violating physics from B-CP anomalies
• Pseudoscalar Higgs Bosons at the LHC: Production and Decays into Electroweak Gauge Bosons Revisited
• Constraining the mixing matrix for Standard Model with four generations: time dependent and semi-leptonic CP asymmetries in $B_d^0$, $B_s$ and $D^0$
• Four Generations, Higgs Physics, and the MSSM
• Fourth Generation Bound States
• Searches for the $t^{\prime }$ of a fourth family
• The Fourth Generation t-prime in Extensions of the Standard Model

Cited by in corpus (7)

• Implications of gauge-mediated supersymmetry breaking with vector-like quarks and a ~125 GeV Higgs boson
• Higgs data does not rule out a sequential fourth generation with an extended scalar sector
• Fourth Generation Parity
• Search for the Anomalous Interactions of Up-Type Heavy Quarks in $\gamma \gamma$ Collision at the LHC
• The 125 GeV Higgs in the context of four generations with 2 Higgs doublets
• Observation of CP violation in $D^0\to K^{-}{\pi }^{+}$ as a smoking gun for New Physics
• Hybrid dynamical electroweak symmetry breaking with heavy quarks and the 125 GeV Higgs