Testing Technicolor with Scalars at the First Muon Collider

An interesting class of models of dynamical electroweak symmetry breaking allows only the third generation fermions to acquire dynamical masses, such that the masses of the first two generations should be given by coupling to a nonstandard ``Higgs'' doublet. The scalars in this case have large couplings to the second generation, so that they are copiously produced at a muon collider. We analyze the potential for discovery of the neutral scalars in the $s$-channel, and we show that at resonance there will be observed in excess of $10^5$ events per year.Comment: 8 pages, latex, aipproc.st

Unscrambling New Models for Higher-Energy Physics

There is strong evidence that new physical degrees of freedom and new phenomena exist and may be revealed in future collider experiments. The best hints of what this new physics might be are provided by electroweak symmetry breaking. I briefly review certain theories for physics beyond the standard model, including the top-quark seesaw model and universal extra dimensions. A common feature of these models is the presence of vector-like quarks at the TeV scale. Then I discuss the role of a linear $e^+e^-$ collider in disentangling this new physics.Comment: 10 pages, LaTeX, uses aipproc.cls and aipproc.sty. Plenary talk given at the 5th International Linear Collider Workshop, Fermilab, Oct. 24-28, 200

Negative contributions to S in an effective field theory

We show that an effective field theory that includes non-standard couplings between the electroweak gauge bosons and the top and bottom quarks may yield negative contributions to both the S and T oblique radiative electroweak parameters. We find that that such an effective field theory provides a better fit to data than the standard model (the chi-squared per degree of freedom is half as large). We examine in some detail an illustrative model where the exchange of heavy scalars produces the correct type of non-standard couplings.Comment: 12 pages, 1 fig., LaTeX, typos corrected, improved referencin

GeV-scale dark matter: production at the Main Injector

Assuming that dark matter particles interact with quarks via a GeV-scale mediator, we study dark matter production in fixed target collisions. The ensuing signal in a neutrino near detector consists of neutral-current events with an energy distribution peaked at higher values than the neutrino background. We find that for a $Z'$ boson of mass around a few GeV that decays to dark matter particles, the dark matter beam produced by the Main Injector at Fermilab allows the exploration of a range of values for the gauge coupling that currently satisfy all experimental constraints. The NO$\nu$A detector is well positioned for probing the presence of a dark matter beam, while future LBNF near-detectors would provide more sensitive probes.Comment: 25 pages, 9 figure