The realization of tunable, ultrashort pulse x-ray sources promises to open new venues of science and to shed new light on long-standing problems in condensed matter physics and chemistry. Fundamentally new information can now be accessed. Used in a pump-probe spectroscopy, ultrashort x-ray pulses provide a means to monitor atomic rearrangement and changes in electronic structure in condensed-matter and chemical systems on the physically-limiting time-scales of atomic motion. This opens the way for the study of fast structural dynamics and the role they play in phase transitions, chemical reactions and the emergence of exotic properties in materials with strongly interacting degrees of freedom. The ultrashort pulse x-ray source developed at the Advanced Light Source at the Lawrence Berkeley Laboratory is based on electron slicing in storage rings, and generates {approx}100 femtosecond pulses of synchrotron radiation spanning wavelengths from the far-infrared to the hard x-ray region of the electromagnetic spectrum. The tunability of the source allows for the adaptation of a broad range of static x-ray spectroscopies to useful pump-probe measurements. Initial experiments are attempted on transition metal complexes that exhibit relatively large structural changes upon photo-excitation and which have excited-state evolution determined by strongly interacting structural, electronic and magnetic degrees …

In this thesis the first measurement of {sigma}(p{bar p}) {yields} Z{sup 0} {yields} {tau}{bar {tau}} with the D0 detector at the Tevatron is presented. The tau pair candidates are recorded by the D0 detector using p{bar p} interactions at a center-of-mass energy of 1.96 TeV. Events in which one tau decays into a muon and the other tau final state is hadronic with one charged particle are selected for this analysis. The selection criteria for the hadronic tau decay are based on the tau final state, hence for two channels of one-prong taus: single charged pion ({tau}{sub {pi}}) and rho decays ({tau}{sub {rho}}). The selection is based on simple cuts on a number of discriminating variables and the cut values have been optimized for the best cross section measurement. Of hadronic tau candidates that have been reconstructed as {tau}{sub {pi}} candidates, 0.801 {+-} 0.017 {+-} 0.066 pass the selection cut; in the case of {tau}{sub {rho}} taus, the selection efficiency is 0.676 {+-} 0.009 {+-} 0.009. Of all QCD jets that are reconstructed as hadronic tau candidates, 0.0093 {+-} 0.0002 pass the {tau}{sub {pi}} selection cuts and 0.0122 {+-} 0.0002 the {tau}{sub {rho}} cuts. The cross section has been measured …

In core-collapse supernovae, strong blast waves drive interfaces susceptible to Rayleigh-Taylor (RT), Richtmyer-Meshkov (RM), and Kelvin-Helmholtz (KH) instabilities. In addition, perturbation growth can result from material expansion in large-scale velocity gradients behind the shock front. Laser-driven experiments are designed to produce a strongly shocked interface whose evolution is a scaled version of the unstable hydrogen-helium interface in core-collapse supernovae such as SN 1987A. The ultimate goal of this research is to develop an understanding of the effect of hydrodynamic instabilities and the resulting transition to turbulence on supernovae observables that remain as yet unexplained. In this dissertation, we present a computational study of unstable systems driven by high Mach number shock and blast waves. Using multi-physics radiation hydrodynamics codes and theoretical models, we consider the late nonlinear instability evolution of single mode, few mode, and multimode interfaces. We rely primarily on 2D calculations but present recent 3D results as well. For planar multimode systems, we show that compressibility effects preclude the emergence of a regime of self-similar instability growth independent of the initial conditions (IC's) by allowing for memory of the initial conditions to be retained in the mix-width at all times. The loss of transverse spectral information is demonstrated, …

The theory that describes the fundamental particle interactions is called the Standard Model, which is a gauge field theory that comprises the Glashow-Weinberg-Salam model [1, 2, 3] of the weak and electromagnetic interactions and quantum chromodynamics (QCD) [4, 5, 6], the theory of the strong interactions. The discovery of the W [7, 8] and Z [9, 10] bosons in 1983 by the UA1 and UA2 collaborations at the CERN p{bar p} collider provided a direct confirmation of the unification of the weak and electromagnetic interactions. Since then, many experiments have refined our understanding of the characteristics of the W and Z bosons.