Detecting Fourth Generation Quarks at Hadron Colliders

Abstract

We consider the phenomenology of the fourth generation heavy quarks which would be pair produced at the LHC. We show that if such a quark with a mass in the phenomenologically interesting range of 400 GeV--600 GeV decays to a light quark and a W-boson, it will produce a signal in a number of channels which can be seen above the background from the three generation Standard Model processes. In particular, such quarks could be seen in channels where multiple jets are present with large missing momentum and either a single hard lepton, an opposite sign hard lepton pair or a same sign lepton pair. In the same sign dilepton channel there is little background and so an excess of such pairs at large invariant mass will indicate the presence of heavy down type quarks. More generally, in our study, the main tool we use to determine the mass of the heavy quark in each of the channels we consider is to use the kinematics of the decay of such quarks to resolve the momenta of the unobserved neutrinos. We show how this can be carried out, even in cases where the kinematics is under-determined by use of the approximation, which holds quite well, that the two heavy quarks are nearly at rest in the center of mass frame. Since it is very likely that at least the lightest heavy quark decays in the mode we consider, this means that it should be observed at the LHC. Indeed, it is expected that the mass splitting between the quarks is less than $m_W$ so that if the Cabbibo-Kobayshi-Maskawa (CKM) matrix element between the fourth and lower generations are not too small, both members of the fourth generation quark doublet will decay in this way. If this is so, the combined signal of these two quarks will make the signal for the fourth generation somewhat more prominent.

26 pages; 15 Figures; In version 2 we have added some references and corrected some typos; Version 3 we have made minor change to some figure captions

References in corpus (34)

• PYTHIA 6.4 Physics and Manual
• Updated predictions for the total production cross sections of top and of heavier quark pairs at the Tevatron and at the LHC
• Delta F=2 Observables and Fine-Tuning in a Warped Extra Dimension with Custodial Protection
• Anatomy of New Physics in B-Bbar mixing
• LHC Signals for Warped Electroweak Neutral Gauge Bosons
• Collider Signals of Top Quark Flavor Violation from a Warped Extra Dimension
• Rare K and B Decays in a Warped Extra Dimension with Custodial Protection
• Possible Indications of New Physics in Bd-mixing and in sin(2 beta) Determinations
• Less space for a new family of fermions
• LHC Signals for Warped Electroweak Charged Gauge Bosons
• Possible evidence for the breakdown of the CKM-paradigm of CP-violation
• Patterns of Flavour Violation in the Presence of a Fourth Generation of Quarks and Leptons
• Four Generations, the Electroweak Phase Transition, and Supersymmetry
• Experimental constraints on fourth generation quark masses
• Search for heavy bottom-like quarks decaying to an electron or muon and jets in $p\bar{p}$ collisions at $\sqrt{s}=1.96$ TeV
• Electroweak Symmetry Breaking from a Holographic Fourth Generation
• Search for down-type fourth generation quarks with the ATLAS detector in events with one lepton and hadronically decaying W bosons
• The heavy quark search at the LHC
• Source of CP Violation for Baryon Asymmetry of the Universe
• LHC Signatures of a Vector-like b'
• Prospects for top-prime quark discovery at the Tevatron
• Search for heavy vector-like quarks coupling to light quarks in proton-proton collisions at sqrt(s) = 7 TeV with the ATLAS detector
• Dynamical Electroweak Symmetry Breaking with a Heavy Fourth Generation
• Hints for the scale of new CP-violating physics from B-CP anomalies
• Search for a Heavy Bottom-like Quark in pp Collisions at sqrt(s) = 7 TeV
• New Developments in MadGraph/MadEvent
• Perturbativity and a Fourth Generation in the MSSM
• Constraining the mixing matrix for Standard Model with four generations: time dependent and semi-leptonic CP asymmetries in $B_d^0$, $B_s$ and $D^0$
• Null tests of the Standard Model at an International Super $B$ Factory
• Approaching a strong fourth family
• Searches for the $t^{\prime }$ of a fourth family
• Measuring the Magnitude of the Fourth-Generation CKM4 Matrix Element V_{t'b'}
• Threshold Effects in the Decay of Heavy b' and t' Quarks
• Bounding CKM Mixing with a Fourth Family

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• Unsolved problems in particle physics
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