DOCSLIB.ORG

Strong Top Dynamics in Light of LHC Data

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Strong Top Dynamics in Light of LHC Data Strong Top Dynamics in Light of LHC Data Elizabeth H. Simmons Michigan State University - EWSB and Strong Top Quark Dynamics - Models - States Connected to the New Dynamics - LHC Prospects - Conclusions JLAB 4 April 2012 Looking Beyond the Standard Model technicolor topcolor susy extra dim. Fundamental scalars observed? Hierarchy/Naturalness? Triviality? Dynamics causing EWSB? EWSB and Strong Top Quark Dynamics Dynamical EWSB: Technicolor: (inspired by QCD) Introduce SU(N)TC with technigluons, inspired by QCD gluons techniquarks carrying SU(N)TC charge: • e.g. weak doublet TL = (UL, DL); weak singlet UR, DR • Lagrangian has SU(2)L x SU(2)R chiral symmetry SU(N)TC gauge coupling becomes large at Λ 1TeV TC ≈ • ! T L T R "≈ 250 GeV causes EWSB • `technipions’ Π TC become the WL, Z L Susskind, Weinberg Dynamical Fermion Masses: ETC* METC > ΛTC ETC boson technigluon E.g. the top quark mass arises from: gETC 2 and its size is ( ) !TT¯ " x (flavor-dependent factor) METC Challenge: ETC must violate custodial symmetry to make mt >> mb. But how to avoid large changes to ∆ ρ ? *Dimpoulos & Susskind; Eichten & Lane Isospin Violation (I) mt = 172 GeV References Isospin Violation (2) Conclusion: t,b feel a Text new strong force not shared by other quarks References or technifermions Top Condensation and EWSB If the top quark feels a new strong interaction, a top-quark condensate can provide some or even all of electroweak symmetry breaking v2 = f 2 + f 2 sin ! f /v TC t ⌘ t some (topcolor*, topcolor-assisted technicolor*) in these models the top quark feels an additional gauge interaction that causes top condensation all (top mode^, top seesaw^^) in top seesaw models, a heavy partner quark T forms the condensate; the top quark mass eigenstate that we observe is a seesaw mixture between T and the standard model’s top quark gauge eigenstate * Hill ^Bardeen,Hill &Lindner; Yamawaki; Miranski; Nambu ^^Chivukula, Dobrescu, Georgi & Hill Physical Realization: Topcolor One physical realization of a new interaction for top is a (spontaneously broken) extended color gauge group: topcolor M SU(3)h SU(3)` SU(3) ⇥ ! QCD where (t,b) feel SU(3)h and (u,c,d,s) feel SU(3)l Below the scale M, exchange of massive topgluons 4⇡ λa 2 t¯γ t yields four-fermion interactions among top quarks − M 2 µ 2 ✓ ◆ Note: M >> 1TeV implies fine tuning Models Hill hep-ph/9411426 Dobrescu & Hill hep-ph/9712319 Chivukula, Christensen, Coleppa, Simmons arXiv:0906.5667 Chivukula, Coleppa, Logan, Martin, Simmons arXiv:1101.6023 Topcolor-Assisted Technicolor (TC2) technicolor: provides most of EWSB topcolor: provides most of mt hypercharge: keeps mb small C.T. Hill Pure Top Condensation? The relationship between v, M, and mt when strong topcolor dynamics causes top condensation and EWSB Pagels-Stokar formula (1979) in NJL approximation 175 Top Seesaw 175 Dobrescu & Hill hep-ph/9712319; Chivukula et al. 9809470; Collins, Grant, Georgi 9908330; He, Hill, Tait 0108041 Effective Theory: “Top Triangle Moose” Gauge structure: ψL0 f-constants of SU(2) × SU(2) × U(1) 0 ⌃01, ⌃12 are g0,g2 ! g1 g vp2 cos ω 01 Top-Higgs Φ = v sin ! ~ ψL1 h i g 1 ψR1 Gauge boson spectrum: photon, Z, Z’, W, W’ g’ 12 (as in 3-site, BESS or HLS) 2 Fermion spectrum: t, T, b, B; similar for light tR2,bR2 quarks & leptons only top couples to Φ Triangle Moose and Topcolor-Assisted TC ψL0 0 g 01 ~ ψL1 Topcolor g 1 (E)TC sector ψR1 sector g’ 12 { 2 } tR2,bR2 This effective theory can interpolate between the TC2 and top seesaw models New States Connected to Top Dynamics topgluon / coloron: Ca • can be flavor (non)universal fractional shift in ✏tL to help Rb agree with data top-Higgs state: Ht 0.7 • production in gg → Ht higher 1 than in SM by factor[sin !]− 0.6 0 top-Pion states: ⇧t±, ⇧t 0.5 w one-loop Rb contributions 0 • sin 0 minimized by (tree) non-ideal 0.4 delocalization of tL as indicated in plot at right: 0.3 0.20.2 0.6 0.4 top’s seesaw partner: T 0.8 0.4 sin ! 0.2 1 0.6 200 400 600 800 1000 can be produced at LHC M GeV • Pt M⇧t H L LHC vs. Colorons ATLAS: CERN-PH-EP-2011-127 CMS: CERN-PH-EP/2011-119 Braam, Chivukula, DiChiara, Flossdorf, Simmons arXiv:0711.1127 Han, Lewis, Liu arXiv:1010.4309 Chivukula, Farzinnia, Foadi, Simmons arXiv:1111.7261 Limits on Topgluons / Colorons 7 conducted on random samples of events generated from our smooth background parameter- Flavor-universal colorons:ization. The use of wide jets instead of AK7 jets improves the expected upper limits on the resonance cross section by roughly 20% for gg, 10% for qg, and 5%4 for qq resonances. • LHC searches for colorons in dijet constrain MC > 2.5 TeV String Resonance q* s8 Excited Quark 3 (pb) [pb] [pb] 3 Axigluon/Coloron 10 A 10 E Diquark A 1 Observed 95% CL upper limit6 Observed 95% CL upper limit W’ × × × Expected 95% CL upper limit Expected 95% CL upper limit Z’ σ σ 2 RS Graviton 2 B 10 68% and 95% bands 10 68% and 95% bands × 10 10 -1 ATLAS 10 ATLAS -1 -1 L dt = 1.0 fb -1 L dt = 1.0 fb 1 ∫ CMS (1.0 fb ) ∫ s = 7 TeV 1 s = 7 TeV s = 7 TeV 10-1 |η| < 2.5, |Δη| < 1.3 -1 Cross Section 95% CL Upper Limit 10 10-2 Gluon-Gluon -2 10 Quark-Gluon Quark-Quark 10-2 1000 2000 3000 4000 10001000 2000 1500 2000 3000 2500 3000 4000 3500 4000 Mass [GeV] ResonanceMass [GeV] Mass (GeV) (a)Excited-quark and axigluon models. Figure 5: The 95% CL upper(b)Colour limits octet on scalars model.B A for dijet resonances of type gluon-gluon (open ⇥ ⇥ circles), quark-gluon (solid circles), and quark-quark (open boxes), compared to theoretical pre- FIG.Topgluons 2. The 95% CL upper coupled limits on σ preferentiallyas a functiondictions of particle for string massto resonances (black3rd filled generation: [3], circles). E6 diquarks The black [5], dotted excited curve quarks shows [6], axigluons [8], colorons [9], the 95% CL upper limit expected from× MonteA Carlo and the light and dark yellow shaded bands represent the 68% and 95% new gauge bosons W0 and Z0 [10], and Randall-Sundrum gravitons [11]. contoursFCNC of the expected bounds limit, respectively. from Theoretical B-mesonpredictions mixing: for σ are M shownC > in (a)6 forTeV excited quarks (blue dashed) and• axigluons (green dot-dashed), and in (b) for colour octetscalarresonances(bluedashed).Foragivennewphysicsmo× A del, the observed (expected) limit occurs at the crossing of its σ curve with the observed (expected) 95% CL upper limit curve. Fits of TC2 to precision electroweak× A data: MC ~ 18 TeV • Table 2: For each model we list the observed and expected upper values of the excluded mass derived from MC simulations. A prior probabilityrange den- at 95%of model CL. The parameters, lower value of ofPDF the set, excluded and of mass MC tune. range Pre- from this search is 1 TeV. sity constant in all positive values of signal cross section, vious ATLAS studies have already explored the impact and zero at negative values, is used. The posterior prob- of different MC tunes and PDF sets on the q∗ theoretical ability is then integrated to determine the 95% CL for a prediction [4]. Model Excluded Mass (TeV) given range of models, usually parameterised by the mass In 2011, the instantaneous luminosityObserved has risenExpected to a of the resonance. level where correctionsString Resonances must be made for multiple4.00 pp col-3.90 Limits are determined on σ for a hypothetical new lisions occurring inE theDiquarks same bunch crossing3.52 (“pileup”),3.28 ×A 6 particle decaying into dijets. The acceptance includes all whose presence aExcitedffects the Quarks measurement2.49 of calorimeter2.68 reconstruction steps and analysis cuts described above, energy depositionsAxigluons/Colorons associated with the hard-scattering2.47 2.66 and assumes that the trigger is fully efficient. (The effi- event under study.W’ All Bosons simulated samples1.51 used in this1.40 ciency is greater than 99% for all analyses.) analysis include a Poisson distributed number of MC The effects of systematic uncertainties due to the minimum bias events added to the hard interaction to knowledge of the luminosity and of the jet energyIn scale Fig. 5 weaccount compare for the “in-time” observed pileup upper caused limits by to additional the model colli- predictions as a function of reso- (JES) are included. The luminosity uncertainty fornance the mass.sions The in predictions the same bunch are from crossing. lowest-order Further calculations account must [24] of the product s B A be taken of “out-of-time” pileup originating from colli- ⇥ ⇥ 2011 data is 3.7% [35]. The systematic uncertaintyusing on CTEQ6L1 parton distributions [19]. New particles are excluded at the 95% CL in mass re- sions in bunches preceding or following the one of inter- the JES is taken from the 2010 data [18] analysis,gions and for which the theory curve lies above our upper limit for the appropriate pair of partons. is adapted to the 2011 analysis taking into account in est, due to the long response time of the liquid argon We also determinecalorimeters. the expected With the lower 50 ns limit bunch on spacing the mass in of the each LHC new particle by comparing the particular the new event pileup conditions (describedexpected be- cross section limits to the model predictions.
Load more

Recommended publications
  • Search for Exotics with Top at ATLAS
    Search for exotics with top at ATLAS Diedi Hu Columbia University On behalf of the ATLAS collaboration EPSHEP2013, Stockholm July 18, 2013 Motivation Motivation Due to its large mass, top quark offers a unique window to search for new physics: mt ∼ ΛEWSB (246GeV): top may play a special role in the EWSB Many extensions of the SM explain the large top mass by allowing the top to participate in new dynamics. Approaches of new physics search Measure top quark properties: check with SM prediction. Directly search for new particles coupling to top tt resonances searches Search for anomalous single top production Vector-like quarks searches (Covered in another talk "Searches for fourth generation vector-like quarks with the ATLAS detector") Search for exotics with tt and single top D.Hu, Columbia Univ. 2 / 16 tt resonance search with 14.3 fb−1 @ 8TeV tt resonance: benchmark models 2 specific models used as examples of sensitivity Leptophobic topcolor Z 0 [2] Explains the top quark mass and EWSB through top quark condensate Z 0 couples strongly only to the first and third generation of quarks Narrow resonance: Γ=m 1:2% ∼ Kaluza-Klein gluons [3] Predicted by the Bulk Randall-Sundrum models with warped extra dimension Strongly coupled to the top quark Broad resonance: Γ=m 15% ∼ Search for exotics with tt and single top D.Hu, Columbia Univ. 3 / 16 tt resonance search with 14.3 fb−1 @ 8TeV tt resonance: lepton+jets(I) [4] Backgrounds SM tt, Z+jets, single top, diboson and W+jets shape: directly from MC W+jets normalization, multijet: estimated from data Event selection One top decays hadronically and The boosted selection the other semileptonically.
    [Show full text]
  • ``Topcolor''; Invited Talk Presented At" Strongly Coupled Gauge Theories
    FERMILAB-Conf-97/032-T TOPCOLOR1 CHRISTOPHER T. HILL Fermi National Accelerator Laboratory P.O. Box 500, Batavia, Illinois, 60510, USA We review a class of dynamical models in which top condensation occurs at the weak scale, giving rise to the large top quark mass and other phenomena. This typically requires a color embedding, SU(3) SU(3)1 SU(3)2, ergo “Topcolor.” Topcolor suggests c → × a novel route to technicolor models in which sequential quarks condense under the Topcolor interaction to break electroweak symmetries. 1 Top Quark Condensation 1.1 Preliminary The top quark has arrived with a mass of 175 GeV. This is remarkably ∼ large in comparison to all other known fundamental particles, and coin- cidently equals the natural scale of electroweak interactions, 1/ 2√2GF . The top quark mass may be dynamically generated, analogousq to a con- stituent quark mass in QCD. Then the relevant question becomes: “Are arXiv:hep-ph/9702320v1 12 Feb 1997 there new strong interactions that are revealing themselves through the large top mass?” If the answer is no, then the most sensible scenario for physics beyond the standard model is something like the minimal supersymmetric standard model (MSSM). In this case the top quark mass is given by the infra–red renormalization group fixed point [1], and many of the successful predictions of unification are tied to this fact [2]. By itself, this is remarkable, because the infra–red renormalization group fixed point is really a consequence of the approximate scale invariance of the unified theory over the range of 1Invited Talk presented at Strongly Coupled Gauge Theories ‘96, Nagoya, Nov.
    [Show full text]
  • Two Composite Higgs Doublets: Is It the Low Energy Limit of A
    Two Composite Higgs Doublets: Is it the Low Energy Limit of a Natural Strong Electroweak Symmetry Breaking Sector ? Alfonso R. Zerwekh∗ Centro de Estudios Subat´omicos and Instituto de F´ısica, Facultad de Ciencias, Universidad Austral de Chile, Casilla 567, Valdivia,Chile Abstract In this paper, we propose an effective model scheme that describes the electroweak symmetry breaking sector by means of composite Higgs- like scalars, following the ideas of Minimal Walking Technicolor (MWT). We argue that, because of the general failure of Extended Technicolor (ETC) to explain the mass of the top quark, it is necessary to introduce two composite Higgs bosons: one of them originated by a MWT-ETC sector and the other one produced by a Topcolor sector. We focus on the phenomenological differences between the light composite Higgs present in our model and the fundamental Higgs boson predicted by the Standard Model and their production at the LHC. We show that in this scheme the main production channel of the lighter Higgs boson are the associated production with a gauge boson and WW fusion but not the gluon-gluon fusion channel which is substantially suppressed. 1 Introduction arXiv:0907.4690v3 [hep-ph] 25 Dec 2009 High Energy Physics is at the dawn of a new era. In the very near future the LHC will allow us to explore, for the first time, the physics responsible for the electroweak symmetry breaking. We are quite sure that something different to the minimal Higgs sector of the Standard Model will be found, but the conjectured alternatives, far from being unique, are varied and very different among them, going from Higgsless models to Supersymmetry.
    [Show full text]
  • Higgs Bosons Strongly Coupled to the Top Quark
    CERN-TH/97-331 SLAC-PUB-7703 hep-ph/9711410 November 1997 Higgs Bosons Strongly Coupled to the Top Quark Michael Spiraa and James D. Wellsb aCERN, Theory Division, CH-1211 Geneva, Switzerland bStanford Linear Accelerator Center Stanford University, Stanford, CA 94309† Abstract Several extensions of the Standard Model require the burden of electroweak sym- metry breaking to be shared by multiple states or sectors. This leads to the possibility of the top quark interacting with a scalar more strongly than it does with the Stan- dard Model Higgs boson. In top-quark condensation this possibility is natural. We also discuss how this might be realized in supersymmetric theories. The properties of a strongly coupled Higgs boson in top-quark condensation and supersymmetry are described. We comment on the difficulties of seeing such a state at the Tevatron and LEPII, and study the dramatic signatures it could produce at the LHC. The four top quark signature is especially useful in the search for a strongly coupled Higgs boson. We also calculate the rates of the more conventional Higgs boson signatures at the LHC, including the two photon and four lepton signals, and compare them to expectations in the Standard Model. CERN-TH/97-331 SLAC-PUB-7703 hep-ph/9711410 November 1997 †Work supported by the Department of Energy under contract DE-AC03-76SF00515. 1 Introduction Electroweak symmetry breaking and fermion mass generation are both not understood. The Standard Model (SM) with one Higgs scalar doublet is the simplest mechanism one can envision. The strongest arguments in support of the Standard Model Higgs mechanism is that no experiment presently refutes it, and that it allows both fermion masses and electroweak symmetry breaking.
    [Show full text]
  • Model-Independent Constraints on Topcolor from Rb
    MADPH-97-984 TUM-HEP-267/97 hep-ph/9702265 Model-independent Constraints on Topcolor from Rb Gustavo Burdman∗ Department of Physics, University of Wisconsin, Madison, WI 53706, USA and Dimitris Kominis† Institut f¨ur Theoretische Physik, Technische Universit¨at M¨unchen, James-Franck-Straße, 85748 Garching, Germany Abstract arXiv:hep-ph/9702265v2 8 May 1997 We identify and compute the main corrections to Rb in Topcolor theories. They are due to the top-pions, the pseudo-Goldstone bosons associated with the chiral symmetry breaking responsible for the top quark mass, and amount to (1 4)%, − − independent of the details of the Topcolor model. We show that the cancellation of this effect against the contributions from Topcolor vector and scalar resonances is unlikely, given the inherently distinct character of the two scales governing the potentially cancelling terms. The resulting value of Rb leads to severe constraints on Topcolor theories. ∗e-mail address: [email protected] †e-mail address: [email protected] 1 Introduction The large value of the top-quark mass has led to speculation that the properties of the top quark may be fundamentally different from those of the other known fermions. In theories of top condensation, for example, a new strong gauge interaction (Topcolor), which couples to the t-quark and perhaps to other fermions as well, drives the formation of a tt¯ condensate and imparts a large dynamical mass to the top quark. In the process, h i the chiral symmetries associated with the strongly interacting fermions are spontaneously broken and at least three Goldstone bosons emerge.
    [Show full text]
  • The Higgs Boson in the Periodic System of Elementary Particles
    Southern Adventist University KnowledgeExchange@Southern Faculty Works Physics and Engineering Department 3-2013 The iH ggs Boson in the Periodic System of Elementary Particles Ding-Yu Chung Ray Hefferlin Follow this and additional works at: https://knowledge.e.southern.edu/facworks_physics Part of the Elementary Particles and Fields and String Theory Commons Recommended Citation Chung, Ding-Yu and Hefferlin, Ray, "The iH ggs Boson in the Periodic System of Elementary Particles" (2013). Faculty Works. 12. https://knowledge.e.southern.edu/facworks_physics/12 This Article is brought to you for free and open access by the Physics and Engineering Department at KnowledgeExchange@Southern. It has been accepted for inclusion in Faculty Works by an authorized administrator of KnowledgeExchange@Southern. For more information, please contact [email protected]. Journal of Modern Physics, 2013, 4, 21-26 doi:10.4236/jmp.2013.44A004 Published Online April 2013 (http://www.scirp.org/journal/jmp) The Higgs Boson in the Periodic System of Elementary Particles Ding-Yu Chung1, Ray Hefferlin2 1Utica, Michigan, USA 2Department of Physics, Southern Adventist University, Collegedale, USA Email: [email protected], [email protected] Received February 12, 2013; revised March 15, 2013; accepted March 27, 2013 Copyright © 2013 Ding-Yu Chung, Ray Hefferlin. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. ABSTRACT It is proposed that the observed Higgs Boson at the LHC is the Standard Model Higgs boson that adopts the existence of the hidden lepton condensate. The hidden lepton is in the forbidden lepton family, outside of the three lepton families of the Standard Model.
    [Show full text]
  • Outlook Post-Higgs
    Outlook Post-Higgs Christopher T. Hill Fermilab UCLA Higgs Workshop March 22, 2013 A dynamical “Higgs” mechanism was supposed to explain the origin of electroweak mass A dynamical “Higgs” mechanism was supposed to explain the origin of electroweak mass We now know that, evidently, a fundamental Higgs Boson exists and explains the masses of quarks, leptons, W and Z A dynamical “Higgs” mechanism was supposed to explain the origin of electroweak mass We now know that, evidently, a fundamental Higgs Boson exists and explains the masses of quarks, leptons, W and Z The Higgs Boson does NOT explain the origin of the electroweak mass-scale A dynamical “Higgs” mechanism was supposed to explain the origin of electroweak mass We now know that, evidently, a fundamental Higgs Boson exists and explains the masses of quarks, leptons, W and Z The Higgs Boson does NOT explain the origin of the electroweak mass-scale i.e., what is the origin of the Higgs Boson mass itself? A dynamical “Higgs” mechanism was supposed to explain the origin of electroweak mass We now know that, evidently, a fundamental Higgs Boson exists and explains the masses of quarks, leptons, W and Z The Higgs Boson does NOT explain the origin of the electroweak mass-scale i.e., what is the origin of the Higgs Boson mass itself? This may present opportunities for a deeper understanding QCD beautifully explains the origin of strong mass : The magnificent scale anomaly: The scale current: = 0 in a scale invariant theory The magnificent scale anomaly: The scale current: = 0 in a scale invariant
    [Show full text]
  • Single Top Production Associated with a Neutral Scalar at LHC in Topcolor-Assisted Technicolor
    Chinese Physics C (HEP & NP) Vol. 32, No. 9, Sep., 2008 Single top production associated with a neutral scalar at LHC in topcolor-assisted technicolor LIU Guo-Li(7Iw)1 ZHANG Huan-Jun(Ü)2;1) 1 (Department of Physics, Zhengzhou University, Henan 450052, China) 2 (Department of Physics, Henan Normal University, Xinxiang 453007, China) Abstract The topcolor-assisted technicolor (TC2) model predicts a number of neutral scalars like the top-pion 0 0 (πt ) and the top-Higgs (ht ). These scalars have flavor-changing neutral-current (FCNC) top quark couplings, among which the top-charm transition couplings may be sizable. Such FCNC couplings induce single top productions associated with a neutral scalar at the CERN Large Hadron Collider (LHC) through the parton ! 0 ! 0 processes cg tπt and cg tht . In this paper we examine these productions and find their production rates can exceed the 3σ sensitivity of the LHC in a large part of parameter space. Since in the Standard Model and the minimal supersymmetric model such rare productions have unobservably small production rates at the LHC, these rare processes will serve as a good probe for the TC2 model. Key words top quark, technicolor, LHC PACS 14.65.Ha, 12.60.Fr, 12.60.Jv As the heaviest fermion in the Standard Model ated with a neutral scalar at the LHC through the 0 0 (SM), the top quark may be a sensitive probe of new parton processes cg tπt and cg tht . In this pa- [1] ! ! physics . So far there remain plenty of room for new per we examine these productions and figure out if physics in top quark sector due to the small statis- their rates can exceed the 3σ sensitivity of the LHC.
    [Show full text]
  • Symmetry Breaking and Generational Mixing in Topcolor--Assisted
    BUHEP–96–2 hep-ph/9602221 Symmetry Breaking and Generational Mixing in Topcolor–Assisted Technicolor Kenneth Lane† Department of Physics, Boston University 590 Commonwealth Avenue, Boston, MA 02215 Abstract Topcolor–assisted technicolor provides a dynamical explanation for electroweak and flavor symmetry breaking and for the large mass of the top quark without unnatural fine tuning. A major challenge is to generate the observed mixing between heavy and light generations while breaking the strong topcolor interactions near 1 TeV. I argue that these phenomena, as well as electroweak symmetry breaking, are intimately connected and I arXiv:hep-ph/9602221v1 4 Feb 1996 present a scenario for them based on nontrivial patterns of technifermion condensation. I also exhibit a class of models realizing this scenario. This picture leads to a rich phe- nomenology, especially in hadron and lepton collider experiments in the few hundred GeV to few TeV region and in precision electroweak tests at the Z0, atomic parity violation, and polarized Møller scattering. 2/96 † [email protected] 1. Introduction Topcolor–assisted technicolor (TC2) was proposed by Hill [1] to overcome major shortcomings of top–condensate models of electroweak symmetry breaking [2], [3] and of technicolor models of dynamical electroweak and flavor symmetry breaking [4], [5]. Technicolor and extended technicolor (ETC) have been unable to provide a natural and plausible understanding of why the top quark mass is so large [6]. On the other hand, models in which strong topcolor interactions drive top–quark condensation and elec- troweak symmetry breaking are unnatural. To reproduce the one–Higgs–doublet standard model consistent with precision electroweak measurements (especially of the parameter 2 2 2 ρ = M /M cos θW 1), the topcolor energy scale must be much greater than the W Z ≃ electroweak scale of (1 TeV).
    [Show full text]
  • Anatomy of Top-Mode Extended Technicolor Model
    December 9, 2018 Anatomy of Top-Mode Extended Technicolor Model ∗ Hidenori Fukano† and Koichi Yamawaki‡ Department of Physics, Nagoya University Nagoya 464-8602, Japan Abstract We analyze two versions of the extended technicolor (ETC) incorporating the top quark condensate via the flavor-universal coloron type topcolor SU(3) 1 × SU(3)2: A straightforward top-mode ETC having quarks and techniquarks as- signed to a single (strong) SU(3)1, and a “twisted model” with techniquarks carrying the weak SU(3)2 while quarks the strong SU(3)1. The straightforward model has the same ETC structure as that of Appelquist et al. without top- color which we first analyze to find that it yields only too small ETC-induced mass for the third generation. In contrast, our model having topcolor takes the form of a version of the topcolor-assisted technicolor (TC2) after ETC breakings, which triggers the top quark condensate giving rise to a realistic top mass. How- ever, techniquarks have the strong topcolor SU(3)1 in addition to the already strong walking/conformal technicolor, which triggers the techniquark condensate arXiv:0801.3716v2 [hep-ph] 19 Feb 2008 at scale much higher than the weak scale, a disaster. We then consider a “twisted model” of TC2, though not an explicit ETC. We find a new feature that “ETC”- induced quark mass is enhanced to the realistic value by the large anomalous dimension γ 2 of Nambu-Jona-Lasinio-type topcolor interactions. The result m ≃ roughly reproduces the realistic quark masses. We further find a novel effect of the above large anomalous dimension γ 2: The top-pion mass has a universal m ≃ upper bound, mπt < 70 GeV, in the generic TC2 model.
    [Show full text]
  • Search for Top Quark Pair Resonances with the CMS Detector at the LHC
    Search for Top Quark Pair Resonances with the CMS Detector at the LHC Von der Fakult¨atf¨urMathematik, Informatik und Naturwissenschaften der RWTH Aachen University zur Erlangung des akademischen Grades eines Doktors der Naturwissenschaften genehmigte Dissertation vorgelegt von Wael Haj Ahmad aus Edlib/Syrien Berichter: Univ.-Prof. Dr.rer.nat. Achim Stahl Univ.-Prof. Dr.rer.nat. Thomas Hebbeker Tag der m¨undlichen Pr¨ufung:29.05.2013 Diese Dissertation ist auf den Internetseiten der Hochschulbibliothek online verf¨ugbar. Contents Contents vi Abstract vii Zusammenfassung ix 1 Overview 1 1.1 Introduction . .1 1.2 The Standard Model of Particle Physics (SM) . .2 1.3 The Top Quark . .4 1.3.1 Top Quark Pair Production . .4 1.3.2 Top Quark Decay Channels . .7 1.4 Top Quark Pair Resonances . .8 1.4.1 Topcolor Assisted Technicolor Z0 ............9 2 The CMS Detector at the LHC 13 2.1 The Large Hadron Collider . 13 2.2 The CMS Detector . 17 2.2.1 The CMS Requirements . 18 2.2.2 The CMS Coordinates . 20 2.2.3 The CMS Inner Tracking System . 21 2.2.4 The Electromagnetic Calorimeter . 22 iv CONTENTS 2.2.5 The Hadronic Calorimeter . 24 2.2.6 The Superconducting Magnet . 26 2.2.7 The Muon System . 26 2.2.8 The Trigger System . 28 3 Object Identification and Reconstruction 31 3.1 Reconstruction of Tracks . 32 3.2 Reconstruction of Primary Vertices . 35 3.3 Reconstruction and Identification of Muons . 37 3.3.1 Reconstruction of Muons . 37 3.4 Reconstruction of Electrons .
    [Show full text]
  • Search for Pair-Produced Vectorlike B Quarks in Proton-Proton
    EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH (CERN) CERN-PH-EP/2015-170 2018/09/21 CMS-B2G-13-006 Search for pair-produced vectorlikep B quarks in proton-proton collisions at s = 8 TeV The CMS Collaboration∗ Abstract A search for the production of a heavy B quark, having electric charge −1/3 and vec- tor couplings to W, Z, and H bosons, is carried out using proton-proton collision data recorded at the CERN LHC by the CMS experiment, corresponding to an integrated luminosity of 19.7 fb−1. The B quark is assumed to be pair produced and to decay in one of three ways: to tW, bZ, or bH. The search is carried out in final states with one, two, and more than two charged leptons, as well as in fully hadronic final states. Each of the channels in the exclusive final-state topologies is designed to be sensitive to specific combinations of the B quark-antiquark pair decays. The observed event yields are found to be consistent with the standard model expectations in all the fi- nal states studied. A statistical combination of these results is performed, and upper limits are set on the cross section of the strongly produced B quark-antiquark pairs as a function of the B quark mass. Lower limits on the B quark mass between 740 and 900 GeV are set at a 95% confidence level, depending on the values of the branching fractions of the B quark to tW, bZ, and bH. Overall, these limits are the most stringent to date.
    [Show full text]