David Stuart — Page 2

arXiv2009

Effective dynamics for solitons in the nonlinear Klein Gordon Maxwell system and the Lorentz force law

We consider the nonlinear Klein Gordon Maxwell system on four dimensional Minkowski space-time. For appropriate nonlinearities the system admits soliton solutions which are gauge invariant generalizations of the non-topological solitons introduced and studied by T.D. Lee and collaborators for pure complex scalar fields. We develop a rigorous dynamical perturbation theory for these solitons in the small e limit, where e is the electromagnetic coupling constant. The main theorems assert the long time stability of the solitons with respect to perturbation by an external electromagnetic field produced by the background current, and compute their effective dynamics to O(e). The effective dynamical equation is the equation of motion for a relativistic particle acted on by the Lorentz force law familiar from classical electrodynamics.

math-ph↗

arXiv2008

Background Modeling in New Physics Searches Using Forward Events at LHC

We present a method to measure dominant Standard Model backgrounds using data containing high rapidity objects in pp collisions at the Large Hadron Collider. The method is developed for analyses of early LHC data when robustness against imperfections of background modeling and detector simulation can be a key to the discovery of new physics at LHC.

hep-ex↗

arXiv2000

Low-Scale and Gauge-Mediated Supersymmetry Breaking at the Fermilab Tevatron Run II

The prospects for discovering and studying signals of low-scale supersymmetry breaking models at the Tevatron Run II and beyond are explored. These models include gauge-mediated supersymmetry breaking as the most compelling and concrete realization, but more generally are distinguished by the presence of a nearly massless Goldstino as the lightest supersymmetric particle. The next-lightest supersymmetric particle(s) (NLSP) decays to its partner and the Goldstino. Depending on the supersymmetry breaking scale, these decays can occur promptly or on a scale comparable to or larger than the size of a detector. A systematic analysis based on a classification in terms of the identity of the NLSP and its decay length is presented. The various scenarios are discussed in terms of signatures and possible event selection criteria. The Run II and beyond discovery and exclusion reaches, including the effects of background, are detailed for the most compelling cases. In addition to standard event selection criteria based on missing energy and photons, leptons, jets, taus, tagged b-jets, or reconstructed Z-bosons, more exotic signals of metastable NLSPs such as displaced photons, large negative impact parameter tracks, kink tracks, both opposite and same-sign highly ionizing tracks, time of flight measurements, charge-changing tracks, charge-exchange tracks, and same-sign di-top events are investigated. The interesting possibility of observing a Higgs boson signal in events that are efficiently "tagged" by the unique signatures of low-scale supersymmetry breaking is also considered.

hep-ph↗