Searches for new quarks and leptons produced in Z-boson decay

Abrams, G. S.; Ce, Adolphsen; Averill, D.; Ballam, J.; Bc, Barish; Barklow, T.; Barnett, B. A.; Bartelt, J.; Bethke, S.; Blockus, D.; Bonvicini, G.; Boyarski, A. M.; Brabson, B.; Breakstone, A.; Bulos, F.; Burchat, P. R.; Dl, Burke; Rj, Cence; Chapman, J. D.; Chmeissani, M.; Cords, D.; Dp, Coupal; Dauncey, P.; Hc, DeStaebler; De, Dorfan; Jm, Dorfan; Dc, Drewer; Elia, R.; Gj, Feldman; Fernandes, D.; Rc, Field; Wt, Ford; Fordham, C.; Frey, R.; Fujino, D.; Gan, K. K.; Gero, E.; Gidal, G.; Glanzman, T.; Goldhaber, G.; Gómez-Cadenas, J. J.; Gratta, G.; Grindhammer, G.; Grosse‐Wiesmann, P.; Hanson, G.; Harr, R.; Harral, B.; Fa, Harris; Hawkes, C. M.; Hayes, K.; Hearty, C.; Heusch, C.A.; Hildreth,; Himel, T.; Da, Hinshaw; Sj, Hong; Hutchinson, D. P.; Hylen, J.; Innes, W. R.; Rg, Jacobsen; Jaros, J. A.; Ck, Jung; Ja, Kadyk; Kent, J.

doi:10.1103/physrevlett.63.2447

Cited by 41 publications

(6 citation statements)

References 11 publications

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“…In 1989 the Large Electron Position collider (LEP) at CERN and the Stanford Linear Collider (SLC) started e + e − collisions at the Z 0 pole, √ s ≈ 90 GeV. The experiments at these accelerators -ALEPH, DELPHI, OPAL and L3 at LEP, and SLD at SLC -searched for Z 0 → tt events of various topologies [190,191,192,193]. The best lower limit on the top quark mass obtained from these direct searches was 45.8 GeV/c 2 .…”

Section: Early Searchesmentioning

confidence: 99%

Top quark physics in hadron collisions

Wagner¹

2005

Rep. Prog. Phys.

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The top quark is the heaviest elementary particle observed to date. Its large mass makes the top quark an ideal laboratory to test predictions of perturbation theory concerning heavy quark production at hadron colliders. The top quark is also a powerful probe for new phenomena beyond the Standard Model of particle physics. In addition, the top quark mass is a crucial parameter for scrutinizing the Standard Model in electroweak precision tests and for predicting the mass of the yet unobserved Higgs boson. Ten years after the discovery of the top quark at the Fermilab Tevatron top quark physics has entered an era where detailed measurements of top quark properties are undertaken. In this review article an introduction to the phenomenology of top quark production in hadron collisions is given, the lessons learned in Tevatron Run I are summarized, and first Run II results are discussed. A brief outlook to the possibilities of top quark research a the Large Hadron Collider, currently under construction at CERN, is included.PACS numbers: 14.65.Ha Summary and outlook 79Top quark physics in hadron collisions 4 IntroductionThe top quark is the by far heaviest of the six fundamental fermions in the Standard Model (SM) of particle physics. Its large mass made the search for the top quark a long and tedious process, since accelerators with high centre-of-mass energies are needed. In 1977 the discovery of the bottom quark indicated the existence of a third quark generation, and shortly thereafter the quest for the top quark began. Searches were conducted in electron-positron (e + e − ) and protonantiproton (pp) collisions during the 1980s and early 1990s. Finally, in 1995 the top quark was discovered at the Fermilab Tevatron pp collider. Subsequently, its mass was precisely measured to be M top = (178.0 ± 4.3) GeV/c 2 [1]. The relative precision of this measurement (2.4%) is better than our knowledge of any other quark mass. The top quark is about 40 times heavier than the second-heaviest quark, the bottom quark. Its huge mass makes the top quark an ideal probe for new physics beyond the SM.It remains an open question to particle physics research whether the observed mass hierarchy is a result of unknown fundamental particle dynamics. It has been argued that the top quark could be the key to understand the dynamical origin of how particle masses are generated by the mechanism of electroweak symmetry breaking, since its mass is close to the energy scale at which the break down occurs (vacuum expectation value of the Higgs field = 246 GeV) [2]. The most favoured framework to describe electroweak symmetry breaking is the Higgs mechanism. The masses of the Higgs boson, the W boson and the top quark are closely related through higher order corrections to various physics processes. A precise knowledge of the top quark mass together with other electroweak precision measurements can therefore be used to predict the Higgs boson mass. At present, top quarks can only be directly produced at the Tevatron. The physics results of the Tevat...

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Section: Early Searchesmentioning

confidence: 99%

Top quark physics in hadron collisions

Wagner¹

2005

Rep. Prog. Phys.

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“…Starting in September 1989, the experiments at LEP* started collecting Z decay data. Months after the publication of most of the results of this thesis [5], the LEP experiments also published similar results using a much larger sample of Z decays. Chapter 6 also includes comparisons of the Mark II limits with LEP limits.…”

Section: Outline Of Thesismentioning

confidence: 66%

Searches for new quarks and leptons in Z boson decays

Kooten¹,

J²

1990

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Price: Printed Copy A08, Microfiche AOl. fAsia * Ph.D. theiif g : "---'-'-r,ow ry r T(1iS ooeu^r ,V.UM P* Abstract Searches for the decay of Z bosons into pairs of new quarks and leptons in a data sample including 455 hadronic Z decays are presented. The Z bosons were produced in electon-positron annihilations at the SLA.C Linear Collider (SLC) operating in the centerof-mass energy range from 89.2 to 93.0 GeV, and the data collected using the Mark II detector. The Standard Model provides no prediction for fermion masses and does not exclude new generations of fennions. The existence and masses of these new particles may provide valuable information to help understand the pattern of fermion masses, the presence of generations, and physics beyond the Standard Model. Specific searches for top quarks and sequential fourth generation charge -1/3 (!/) quarks are made considering a variety of possible standard and non-standard decay modes. In ad dition, searches for sequential fourth generation massive neutrinos v,i (Dirac and Majorana)and their charged lepton partners L~ are pursued. The i/ 4 may be stable or decay through mixing to the lighter generations. The data sample Is examined for new particle topolo gies of events with high-momentum isolated tracks, high-energy isolated photons, spherical event shapes, and detached vertices. Measurements of the Z boson resonance parameters that provide crucial indicators of new particle production are also considered.No evidence is observed for the production of new quarks and leptons. 95% confidence lower mass limits of 40.7 GeV/c 2 for the top quark and 42.0 GeV/c 2 for the t'-quark mass are obtained regardless of the branching fractions to the considered decay modes. A significant range of mixing matrix elements of v.\ to other generation neutrinos for a v A mass from 1 GeV/c 2 to 43 GeV/c 2 is excluded at 95% confidence level. Measurements of the upper limit of the invisible width of the Z exclude additional values of the u 4 mass and mixing matrix elements, and also permit the exclusion of a region in the L~ mass versus v.\ mass plane.ii These results substantially extend previous limits, and exclude a large fraction of the *.mass range available for Z decays into top quarks and fourth generation quarks and leptons. #"This thesis analysis benefited greatly from illuminating and helpful discussions with several people. The enthusiasm and energy of Tim Barklow, the knowledge of Sachio Komamiya, and the wisdom of a close friend, Chang-Kee Jung have been a source of inspiration for me.I would like to thank the Mark II collaborators for their contributions during the some times frustrating operation of the Mark II detector at the SLC. I am just as grateful for the camaraderie and friendship of my colleagues. My office mates Carrie Fordham and graduate student (now post-doc) extraordinaire, Jordan Nash, provided many interesting conversations and company. , and others too numerous to name have all made for a great experience. I extend my thanks to Anna Pacheco for the countless...

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“…By 1990 experiments at TRISTAN excluded the top quark with mass less than 30.2 GeV [25]. Later, the two e + e − Z boson factories SLC at SLAC and LEP at CERN started operation, and by about 1990 set a lower limit on m t at half of the Z boson mass, m t ≥ 45.8 GeV [26,27,28,29]. In the early 1980s, the SppS collider came into operation at CERN with counter-rotating beams of protons and antiprotons colliding with an energy of 540 GeV (later upgraded to 630 GeV).…”

Section: History Of Searches For the Top Quarkmentioning

confidence: 99%

“…Summary of increasing mass limits of the mass of the top quark m t through 1980s and early 1990s. half of the Z boson mass, m t ≥ 45.8 GeV[26,27,28,29].…”

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confidence: 99%

The top quark (20 years after its discovery)

et al. 2015

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This paper, written to mark the twentieth anniversary of the discovery of the top quark, offers some insight into how the understanding of this heaviest known particle has developed from prediction through search to discovery to the current knowledge of its production mechanisms and properties. The central role of the top quark in the Standard Model is considered, and the window of opportunity it opens for seeking new physics beyond the Standard Model is discussed. Contents 8.1 Standard Model self-consistency: chiral anomalies; 8.2 Flavor changing neutral currents and the GIM mechanism; 8.3 Top-quark Yukawa coupling and consistency of the Standard Model at high energy scales; 8.4 Quantum corrections to electroweak observables 9. Top quark as a window to new physics 1151 9.1 Searches for associated t " t production; 9.2 Searches for non-Standard Model Higgs bosons; 9.3 Searches for supersymmetric partners of the top quark; 9.4 Searches for vector-like quarks; 9.5 Searches for new gauge bosons 10. Conclusions 1154 References 1155

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Searches for new quarks and leptons produced in Z-boson decay

Cited by 41 publications

References 11 publications

Top quark physics in hadron collisions

Top quark physics in hadron collisions

Searches for new quarks and leptons in Z boson decays

The top quark (20 years after its discovery)

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