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The photon polarization in b -> X gamma in the standard model

Description: The standard model prediction for the {bar B}{sup 0} {yields} X{sub s,d}{gamma} decay amplitude with a right-handed photon is believed to be tiny, suppressed by m{sub s,d}/m{sub b}, compared to the amplitude with a left-handed photon. We show that this suppression is fictitious: in inclusive decays, the ratio of these two amplitudes is only suppressed by g{sub s}/(4{pi}), and in exclusive decays by {Lambda}{sub QCD}/m{sub b}. The suppression is not stronger in {bar B}{sup 0} {yields} X{sub d}{gamma} decays than it is in {bar B}{sup 0} {yields} X{sub s}{gamma}. We estimate that the time dependent CP asymmetries in B {yields} K*{gamma}, {rho}{gamma}, K{sub S}{pi}{sup 0}{gamma}, and {pi}{sup +}{pi}{sup -} {gamma} are of order 0.1 and that they have significant uncertainties.
Date: December 8, 2004
Creator: Grinstein, Benjamin; Grossman, Yuval; Ligeti, Zoltan & Pirjol, Dan
Partner: UNT Libraries Government Documents Department

Observation of Secondary Plasma Waves in Laser-Plasma Interaction Experiments

Description: An experiment is described where the two products of the Langmuir Decay Instability (LDI) of a primary electron plasma wave have been observed and identified without any ambiguity. Primary Langmuir waves are driven by Stimulated Raman Scattering (SRS) of an incident laser which provides well-defined electron plasma waves. Thomson scattering of a short wavelength probe beam yields measurements of the amplitude of the waves resolved in time, space, wavelength and wavevector, that allow identification of the probed waves.
Date: December 8, 1999
Creator: Depierreux, S.; Labaune, C.; Baldis, H.A.; Fuchs, J. & Michard, A.
Partner: UNT Libraries Government Documents Department

Twistor String Theory and QCD

Description: The author reviews recent progress in using twistor-inspired methods to compute perturbative scattering amplitudes in gauge theory, for application to collider physics.
Date: December 8, 2005
Creator: Dixon, Lance J.
Partner: UNT Libraries Government Documents Department

Scaling of radial propagating structures in the scrape-off layer of the National Spherical Torus Experiment (NSTX)

Description: The radial propagation of spatiotemporal turbulent structures in the scrape-off layer of the National Spherical Torus Experiment [M. Ono, M.G. Bell, R.E. Bell, et al. Plasma Phys. Control. Fusion 45, A335 (2003)] is investigated. Two-dimensional spatiotemporal imaging of the Dα emission intensity is used to observe the fluctuation structures in the poloidal plane perpendicular to the ambient magnetic field. Turbulent structures are extracted and the individual properties such as velocity, spatial scale and amplitude are determined. The typical poloidal scale of the structures is kϑ = 0.5 cm−1. The poloidal and radial structure velocities are < 5 km/s and 1 km/s, respectively. The radial velocities do not vary significantly with their spatial size within this set of data.
Date: December 8, 2008
Creator: Windisch, T., Grulke, O., Zweben, S.J., and Maqueda, J.R.
Partner: UNT Libraries Government Documents Department

The Velocity Field of the Local Universe From Measurements of Type Ia Supernovae

Description: We present a measurement of the velocity flow of the local universe relative to the CMB rest frame, based on the Jha, Riess & Kirshner (2007) sample of 133 low redshift type Ia supernovae. At a depth of 4500 km s{sup -1} we find a dipole amplitude of 279 {+-} 68 km s{sup -1} in the direction l = 285{sup o} {+-} 18{sup o}, b = -10{sup o} {+-} 15{sup o}, consistent with earlier measurements and with the assumption that the local velocity field is dominated by the Great Attractor region. At a larger depth of 5900 km s{sup -1} we find a shift in the dipole direction towards the Shapley concentration. We also present the first measurement of the quadrupole term in the local velocity flow at these depths. Finally, we have performed detailed studies based on N-body simulations of the expected precision with which the lowest multipoles in the velocity field can be measured out to redshifts of order 0.1. Our mock catalogues are in good agreement with current observations, and demonstrate that our results are robust with respect to assumptions about the influence of local environment on the type Ia supernova rate.
Date: December 8, 2006
Creator: Haugbolle, T.; Hannestad, S.; Thomsen, B.; U., /Aarhus; Fynbo, J.; Inst., /Bohr et al.
Partner: UNT Libraries Government Documents Department