Elizabeth H. Simmons

Strong dynamics and electroweak symmetry breaking

The breaking of electroweak symmetry, and origin of the associated “weak scale,” vweak = 1/ q 2 √ 2GF = 175 GeV, may be due to a new strong interaction. Theoretical developments over the past decade have led to viable models and mechanisms that are consistent with current experimental data. Many of these schemes feature a privileged role for the top quark, and third generation, and are natural in the context of theories of extra space dimensions at the weak scale. We review various models and their phenomenological implications which will be subject to definitive tests in future collider runs at the Tevatron, and the LHC, and future linear e + e − colliders, as well as sensitive

Erosion and molecule formation in condensed gas films by electronic energy loss of fast ions

Abstract Fast ions erode films of molecular and rare gas solids as a result of electronic energy loss of the incident particles. The dependence of the low temperature erosion yield on electronic stopping power is nonlinear and approximately quadratic for light ions. Thermal spike and Coulomb repulsion models for erosion in this temperature regime are discussed. Measurements of ejected species from D 2 O ice eroded by MeV He + ions show a constant and dominant yield of D 2 O molecules below 135 K and a monotonically increasing yield of D 2 and O 2 molecules from 55 to 150 K. The new molecules must result from rearrangement of fragments produced in the film by ionization. The temperature dependence is believed to be due to diffusion controlled migration in the film.

Electronic sputtering of low temperature molecular solids

Electronically stimulated sputtering of insulating molecular gas solids is a remarkably efficient process at excitation densities accessible by MeV light ions and keV electrons. This paper concentrates on the cases of CO and H2O (D2O). The approximately quadratic dependence of sputtering yield on the excitation density along individual particle tracks observed earlier for incident MeV ions has also been found for incident keV electrons in the case of CO. Coupled with time-of-flight energy spectra of ejected D2O from solid D2O, this behavior leads to a picture of rapid electronic relaxation with molecular repulsion involving pairs of molecular ions. We also report a dependence of CO sputtering yield on incident angle for MeV He ions which varies as (cosθ)−1.6, in qualitative support of the multiple ion picture. In addition to ejection of the principal molecular species of a solid film, electronic excitation of molecular solids even at very low temperatures leads to formation of new molecular species by bond disruption and fragment rearrangement. In the case of D2O the dominant new molecules are D2 and O2 whose ejection from the film is strongly thermally activated.

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.

New strong interactions at the Tevatron

Abstract Recent results from CDF indicate that the inclusive cross section for jets with E r > 200 GeV is significantly higher than that predicted by QCD. We describe here a simple flavor-universal variant of the “coloron” model of Hill and Parke that can accommodate such a jet excess, and which is not in contradiction with other experimental data. As such, the model serves as a useful baseline with which to compare both the data and other models proposed to describe the jet excess. An interesting theoretical feature of the model is that if the global chiral symmetries of the quarks remain unbroken in the confining phase of the coloron interaction, it realizes the possibility that the ordinary quarks are composite particles.

Phenomenology of a technicolor model with heavy scalar doublet

Abstract Rather than having a light scalar both break SU(2) × U(1) and give mass to the fermions, as in the standard model, it is possible to use technicolor to do the first while a heavy (∼ 10 TeV) scalar does the second. The impact of such a heavy scalar on FCNC in the Kaon and B-meson systems is explored here.

A heavy top quark and the Zbb vertex in non-commuting extended technicolor

Abstract We explore corrections to electroweak parameters in the context of Extended Technicolor (ETC) models in which the ETC gauge-boson which generates the top-quark mass carries weak SU(2) charge. For mt≈150 GeV there exist potentially large corrections to the Z decay width to b-quarks. Interestingly, in contrast to the situation in ETC models where the gauge-boson which generates the top-quark mass is a weak SU(2) singlet, the corrections may increase the Z→b b branching ratio.

D-D mixing in heavy quark effective field theory; the sequel

Abstract We perform a quantitative analysis of D- D mixing in heavy quark effective field theory (HQEFT) including leading order QCD corrections. We find an enhancement of the short-distance contribution by a factor of two or three.

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.

A Heavy Top Quark From Flavor-Universal Colorons

Author(s): Popovic, Marko B; Simmons, Elizabeth H | Abstract: Ordinary technicolor and extended technicolor cannot produce the heavy top quark unaided. We demonstrate that a flavor-universal extension of the color interactions combined with an extended hypercharge sector that singles out the third generation can provide the necessary assistance. We discuss current experimental constraints and suggest how collider experiments can search for the predicted new heavy gauge bosons.