R. Sekhar Chivukula

Electroweak Fermion Number Violation and the Production of Stable Particles in the Early Universe

The effect of electroweak fermion number violation in the early universe is to distribute a fermion number excess over all the electroweak doublets. If baryogenesis is due to physics above the weak scale, this can result in the production of heavy stable particles in numbers comparable to the number of baryons. In particular, there may be enough stable technibaryons present today to account for the missing mass of the universe.

Top Quark Seesaw Theory of Electroweak Symmetry Breaking

We study electroweak symmetry breaking involving the seesaw mechanism of quark condensation. These models produce a composite Higgs boson involving the left-handed top quark, yet the top mass arises naturally at the observed scale. We describe a schematic model which illustrates the general dynamical ideas. We also consider a generic low-energy effective theory which includes several composite scalars, and we use the effective potential formalism to compute their spectrum. We develop a more detailed model in which certain features of the schematic model are replaced by additional dynamics.

Unitarity of compactified five-dimensional Yang-Mills theory

Abstract Compactified five-dimensional Yang–Mills theory results in an effective four-dimensional theory with a Kaluza–Klein (KK) tower of massive vector bosons. We explicitly demonstrate that the scattering of the massive vector bosons is unitary at tree-level for low energies, and analyze the relationship between the unitarity violation scale in the KK theory and the nonrenormalizability scale in the five-dimensional gauge theory. In the compactified theory, low-energy unitarity is ensured through an interlacing cancellation among contributions from the relevant KK levels. Such cancellations can be understood using a Kaluza–Klein equivalence theorem which results from the geometric “Higgs” mechanism of compactification. In these theories, the unitarity violation is delayed to energy scales higher than the customary limit through the introduction of additional vector bosons rather than Higgs scalars.

CERN LHC signatures of new gauge bosons in the minimal Higgsless model

We study the LHC signatures of new gauge bosons in the gauge-invariant minimal Higgsless model. It predicts an extra pair of W{sub 1} and Z{sub 1} bosons which can be as light as {approx}400 GeV and play a key role in the delay of unitarity violation. We analyze the W{sub 1} signals in pp{yields}W{sub 0}Z{sub 0}Z{sub 0}{yields}jj4l and pp{yields}W{sub 0}Z{sub 0}jj{yields}{nu}3ljj processes at the LHC, including the complete electroweak and QCD backgrounds. We reveal the complementarity between these two channels for discovering the W{sub 1} boson, and demonstrate the LHC discovery potential over the full range of allowed W{sub 1} mass.

Unitarity of deconstructed five-dimensional Yang–Mills theory

Abstract The low-energy properties of a compactified five-dimensional gauge theory can be reproduced in a four-dimensional theory with a replicated gauge group and an appropriate gauge symmetry breaking pattern. The lightest vector bosons in these “deconstructed” or “remodeled” theories have masses and couplings approximately equal to those of the Kaluza–Klein tower of massive vector states present in a compactified higher-dimensional gauge theory. We analyze the unitarity of low-energy scattering of the massive vector bosons in a deconstructed theory, and examine the relationship between the scale of unitarity violation and the scale of the underlying chiral symmetry breaking dynamics which breaks the replicated gauge groups. As in the case of compactified five-dimensional gauge theories, low-energy unitarity is ensured through an interlacing cancellation among contributions from the tower of massive vector bosons. We show that the behavior of these scattering amplitudes is manifest without such intricate cancellations in the scattering of the would-be Goldstone bosons of the deconstructed theory. Unlike compactified five-dimensional gauge theories, the amplitude for longitudinal vector boson scattering in deconstructed theories does grow with energy, though this effect is suppressed by 1/(N+1), with N+1 being the number of replicated gauge groups.

Polychromatic penguins don't fly

Abstract It is shown that the large-N approximation in the standard model predicts much too small a rate for ΔI = 1 2 nonleptonic K decays, even when short-distance QCD effects such as penguins are included. The effects of the penguins are discussed consistently to leading nontrivial order in chiral perturbation theory and it is found that they are completely calculable and small. It is concluded that N = 3 is not large enough to make the large-N approximation useful.

Axigluons cannot explain the observed top quark forward-backward asymmetry

We study an SU(3){sup 2} axigluon model introduced by Frampton, Shu, and Wang [Phys. Lett. B 683, 294 (2010)] to explain the recent Fermilab Tevatron observation of a significant positive enhancement in the top quark forward-backward asymmetry relative to standard model predictions. First, we demonstrate that data on neutral B{sub d}-meson mixing excludes the region of model parameter space where the top asymmetry is predicted to be the largest. Keeping the gauge couplings below the critical value that would lead to fermion condensation imposes further limits at large axigluon mass, while precision electroweak constraints on the model are relatively mild. Furthermore, by considering an extension to an SU(3){sup 3} color group, we demonstrate that embedding the model in an extra-dimensional framework can only dilute the axigluon effect on the forward-backward asymmetry. We conclude that axigluon models are unlikely to be the source of the observed top quark asymmetry.

Deconstructed Higgsless models with one-site delocalization

In this note we calculate the form of electroweak corrections in deconstructed Higgsless models for the case of a fermion whose weak properties arise from two adjacent

Universal non-oblique corrections in Higgsless models and beyond

SU(2)

Aspects of dynamical electroweak symmetry breaking

groups on the deconstructed lattice. We show that, as recently proposed in the continuum, it is possible for the value of the electroweak parameter