Implications of a Running Dark Photon Coupling

For an "invisible" dark photon $Z_d$ that dominantly decays into dark states, the running of its fine structure constant $\alpha_d$ with momentum transfer $q > m_{Z_d}$ could be significant. A similar running in the kinetic mixing parameter $\varepsilon^2$ can be induced through its dependence on $\alpha_d(q)$. The running of couplings could potentially be detected in "dark matter beam" experiments, for which theoretical considerations imply $\alpha_d (m_{Z_d}) \lesssim 0.5$.Comment: 4 pages, 4 figures. Contributed to the 11th Patras Workshop on Axions, WIMPs and WISPs, Zaragoza, Spain, June 22-26, 201

Signals of Warped Top-Condensation in B-Decays

A recently proposed warped top-condensation model generally predicts a light radion \phi, with a mass of a few GeV or less, whose interactions are suppressed by a scale of order 100 TeV. In this talk, we present existing constraints and potential signals from the process b \to s \phi, in the context of such a model. Astrophysical bounds, applicable to very light radions, are also briefly discussed.Comment: Talk given at the SUSY 2009 conference, held at Northeastern University, Boston, MA, USA, June 5-10, 2009. 4 page

Compton Scattering at the NLC and Large Extra Dimensions

We study Compton scattering, gamma e -> gamma e, in the context of the recent proposal for Weak Scale Quantum Gravity (WSQG) with large extra dimensions. It is shown that, with an ultraviolet cutoff $M_S \sim 1$ TeV for the effective gravity theory, the cross section for this process at the Next Linear Collider (NLC) deviates from the prediction of the Standard Model significantly. Our results suggest that, for typical proposed NLC energies and luminosities, WSQG can be tested in the range 4 TeV\lsim M_S \lsim 16 TeV, making gamma e -> gamma e an important test channel.Comment: Latex, 15 pages, 7 figures. New results, figures, and references adde