DYNAMICAL ELECTROWEAK SYMMETRY BREAKING

In this talk I discuss theories of dynamical electroweak symmetry breaking, with emphasis on the implications of a heavy top-quark on the weak-interaction $\rho$ parameter

Technicolor and Lattice Gauge Theory

Technicolor and other theories of dynamical electroweak symmetry breaking invoke chiral symmetry breaking triggered by strong gauge-dynamics, analogous to that found in QCD, to explain the observed W, Z, and fermion masses. In this talk we describe why a realistic theory of dynamical electroweak symmetry breaking must, relative to QCD, produce an enhanced fermion condensate. We quantify the degree to which the technicolor condensate must be enhanced in order to yield the observed quark masses, and still be consistent with phenomenological constraints on flavor-changing neutral-currents. Lattice studies of technicolor and related theories provide the only way to demonstrate that such enhancements are possible and, hopefully, to discover viable candidate models. We comment briefly on the current status of non-perturbative investigations of dynamical electroweak symmetry breaking, and provide a "wish-list" of phenomenologically-relevant properties that are important to calculate in these theoriesComment: Talk given by RSC at the XXVIII International Symposium on Lattice Field Theory, Lattice2010, June 14-19, 2010, Villasimius, Italy. References adde

Condensate Enhancement and D-Meson Mixing in Technicolor Theories

Since the pioneering work of Eichten and Lane it has been known that the scale of the interactions responsible for the generation of the strange-quark mass in extended technicolor theories must, absent any "GIM-like" mechanism for suppressing flavor-changing neutral currents, be greater than of order 1000 TeV. In this note we point out that the constraint from the neutral D-meson system is now equally strong, implying that the charm quark mass must also arise from flavor dynamics at a scale this high. We then quantify the degree to which the technicolor condensate must be enhanced in order to yield the observed quark masses, if the extended technicolor scale is of order 1000 TeV. Our results are intended to provide a framework in which to interpret and apply the results of lattice studies of conformal strongly interacting gauge theories, and the corresponding numerical measurements of the anomalous dimension of the mass operator in candidate theories of "walking" technicolor.Comment: 6 pages, references added and re-ordere

Colorphilic Spin-2 Resonances in the LHC Dijet Channel

Experiments at the LHC may yet discover a dijet resonance indicative of Beyond the Standard Model (BSM) physics. In this case, the question becomes: what BSM theories are consistent with the unexpected resonance? One possibility would be a spin-2 object called the colorphilic graviton--a spin-2 color-singlet particle which couples exclusively to the quark and gluon stress-energy tensors. We assess the possibility of this state's discovery in the dijet channel as an s-channel resonance, and report the regions of parameter space where colorphilic gravitons have not yet been excluded by LHC-13 data but still may be discovered in the dijet channel at LHC-14 for integrated luminosities of 0.3, 1, and 3 ab$^{-1}$. We then delineate which of those regions remain accessible to future collider searches, once one accounts for applicability of the narrow-width approximation, detector mass resolution, and self-consistency according to tree-level partial-wave unitarity. We discover that--despite the strong constraints unitarity imposes on collider searches--the colorphilic graviton remains potentially discoverable in the LHC dijet channel. A means of investigation would be to apply the color discriminant variable (CDV), a dimensionless combination of quantities (cross-section, decay width, and invariant mass) that can be quickly measured after the discovery of a dijet resonance. Previous publications have demonstrated the CDV's utility when applied to theories containing Z', colorons, excited quarks, and diquarks. We extend this analysis to the colorphilic graviton by applying the CDV to the appropriate region of parameter space. We conclude that resolvable, discoverable dijet resonances consistent with colorphilic gravitons span a narrower range of masses than those consistent with leptophobic Z' models, and can be distinguished from those originating from coloron, excited quark, and diquark models.Comment: 23 pages, 4 figures, updated notation and figure

Vacuum Stability and Triviality Analyses of the Renormalizable Coloron Model

The renormalizable coloron model is built around a minimally extended color gauge group, which is spontaneously broken to QCD. The formalism introduces massive color-octet vector bosons (colorons), as well as several new scalars and fermions associated with the symmetry breaking sector. In this paper, we examine vacuum stability and triviality conditions within the context of the renormalizable coloron model up to a cutoff energy scale of 100~TeV, by computing the beta-functions of all relevant couplings and determining their running behavior as a function of the renormalization scale. We constrain the parameter space of the theory for four separate scenarios based on differing fermionic content, and demonstrate that the vectorial scenarios are less constrained by vacuum stability and triviality bounds than the chiral scenarios. Our results are summarized in exclusion plots for the separate scenarios, with previous bounds on the model overlaid for comparison. We find that a 100 TeV hadron collider could explore the entire allowed parameter space of the chiral models very effectively.Comment: 17 pages, embedded color pdf figures. Typos corrected and appendix on fermion charges and mass generation adde

A Flavorful Top-Coloron Model

In this paper we introduce a simple renormalizable model of an extended color gauge sector in which the third-generation quarks couple differently than the lighter quarks. In addition to a set of heavy color-octet vector bosons (colorons), the model also contains a set of heavy weak vector quarks. Mixing between the third-generation of quarks and the first two is naturally small, and occurs only through the (suppressed) mixing of all three generations with the heavy vector quarks. We discuss the constraints on this model arising from limits on flavor-changing neutral currents and from collider searches for the colorons and vector quarks, and discuss the prospects for discovery at the LHC.Comment: 18 pages, 13 pdf included figures. Typos fixed, corresponds to published versio

Same-Sign Dileptons from Colored Scalars in the Flavorful Top-Coloron Model

In this paper we study the phenomenology of color-octet and color-singlet scalars in the flavorful Top-Coloron model. We discuss the relevant production mechanisms at hadron colliders and the dominant decay modes, highlighting the most promising signatures for discovery, and derive bounds on the masses of the new scalars from LHC and Tevatron data. Of particular interest is the case in which color-octet scalars are pair produced and each decay to t cbar or tbar c, leading to a same-sign-dilepton final state. LHC data places a lower limit of 440 GeV on the octet mass in this scenario. The case of an octet lighter than the top, where the octet only decays into jets, has been tested by the Tevatron, which excludes the mass region from 50 to 125 GeV. The 8 TeV LHC is not yet sensitive to the observation of the color-singlet states, which are produced at rates much smaller than the octets. Nevertheless, the color-singlet pseudoscalar can be discovered at the 14 TeV LHC by analyzing the channel where it is produced from the decay of a color-octet vector boson.Comment: 21 pages. Included scalar decay to off-shell t and c, and added results from ATLAS four-jet resonance searc

Technicolor in the LHC Era

LHC searches for the standard model Higgs Boson in \gamma\gamma\ or \tau\tau\ decay modes place strong constraints on the light technipion state predicted in technicolor models that include colored technifermions. Compared with the standard Higgs Boson, the technipions have an enhanced production rate (largely because the technipion decay constant is smaller than the weak scale) and also enhanced branching ratios into di-photon and di-tau final states (largely due to the suppression of WW decays of the technipions). Recent ATLAS and CMS searches for Higgs bosons exclude the presence of technipions with masses from 110 GeV to nearly 2m_t in technicolor models that (a) include colored technifermions (b) feature topcolor dynamics and (c) have technicolor groups with three or more technicolors (N_{TC} > 3).Comment: 15 pages, pdf figures embedded. Contribution to KMI Inauguration Conference "Quest for the Origin of Particles and the Universe" (KMIIN), 24-26 Nov. 2011, KMI, Nagoya Universit