1,317 research outputs found
Interference and Partial Width Asymmetry in Top and Antitop Decays
We re-examine the question of a possible difference in the partial decay
widths of and , induced by an intermediate scalar boson
with -violating couplings. The interference of and exchanges is
analysed by constructing the propagator matrix of the
system, and determining its absorptive part in terms of fermion loops. Results
are obtained for the partial rate difference in the channels
and , which fulfil explicitly the constraints of
invariance. These results are contrasted with those in previous work.Comment: 14 pages, report PITHA 94/1
Energy Spectra and Energy Correlations in the Decay
It is shown that in the sequential decay , the energy distribution of the final state particles provides
a simple and powerful test of the vertex. For a standard Higgs boson, the
energy spectrum of any final fermion, in the rest frame of , is predicted to
be , with
and . By contrast, the spectrum for a
pseudoscalar Higgs is . There are
characteristic energy correlations between and and between
and . These considerations are applied to the ``gold--plated''
reaction , including possible effects of
CP--violation in the coupling. Our formalism also yields the energy
spectra and correlations of leptons in the decay .Comment: 14 pages + 4 figure
Master of Science
thesisThe Wasatch Mountains are a unique place to study deposition of ions in snow because of proximity to Salt Lake City, UT, home to 1.1 million people, and Great Salt Lake, the world' fourth largest closed-basin saline lake. Prior study at low elevations of the Wasatch Mountains and in Salt Lake City indicates very high deposition (>1 mmol L-1) of chloride nitrate, sulfate, sodium and calcium ions in snow and rime during winter temperature inversions. At peak snowpack, concentrations (?eq L-1) and ecosystem loading (meq m-2) of major ion species (Cl-, NO3-, SO42-, H+, NH4+, Na+, Mg2+, K+, and Ca2+) were measured at five sites in 2008 and 16 sites in 2009 in the Wasatch Mountains. Concentrations and loading of these ion species in snow were up to an order of magnitude higher than previously observed and were likely derived from salts that precipitated from Great Salt Lake as its elevation decreased. Great Salt Lake has very high salinity dominated by concentrations of chloride, sulfate, sodium and magnesium. Moderately strong correlations existed between concentrations of these ions in snow and distance from Great Salt Lake, suggesting it as a major source of ion deposition in the Wasatch Mountains. Concentrations and ecosystem loading of nitrate in snow were lower than expected, but total winter inorganic nitrogen deposition (NO3- and NH4+) was similar to observations at Niwot Ridge in the Rocky Mountains of Colorado. In general, concentrations of ions in snow decreased with elevation while ecosystem loading of ions increased with elevation due to greater snow accumulation
Large Extra Dimension Effects on the Spin Configuration of the Top Quark Pair at e^+ e^- Colliders
Large extra dimension effects on the spin configuration of the top quark pair
at the process are studied. It is shown that the TeV
scale quantum gravity effects cause significant deviations from the Standard
Model predictions for the spin configuration in the off-diagonal basis: they
lead to substantial cross sections of the like-spin states of the top quark
pair, which vanish in the SM; they weaken the pure dominance of the processes,
the Up-Down (Down-Up) spin states for the left-handed (right-handed) beam. In
addition it is shown that the angular cut is very effective
to determine the sign of the quantum gravity corrections.Comment: A discussion on the angular distribution is added with a tabl
Energy correlation and asymmetry of secondary leptons in and
We study the energy correlation of charged leptons produced in the decay of a
heavy Higgs particle and The possible influence of --violation in
the and vertices on the energy spectrum of the secondary
leptons is analyzed. The energy distribution of the charged leptons in the
decay is sensitive to the --parity
of the Higgs particle and yields a simple criterion for distinguishing scalar
Higgs from pseudoscalar Higgs.Comment: 12 pages, + 4 uuencoded figures. report PITHA 94/2
Detaching from the negative by reappraisal: the role of right superior frontal gyrus (BA9/32)
The ability to reappraise the emotional impact of events is related to long-term mental health. Self-focused reappraisal (REAPPself), i.e., reducing the personal relevance of the negative events, has been previously associated with neural activity in regions near right medial prefrontal cortex, but rarely investigated among brain-damaged individuals. Thus, we aimed to examine the REAPPself ability of brain-damaged patients and healthy controls considering structural atrophies and gray matter intensities, respectively. Twenty patients with well-defined cortex lesions due to an acquired circumscribed tumor or cyst and 23 healthy controls performed a REAPPself task, in which they had to either observe negative stimuli or decrease emotional responding by REAPPself. Next, they rated the impact of negative arousal and valence. REAPPself ability scores were calculated by subtracting the negative picture ratings after applying REAPPself from the ratings of the observing condition. The scores of the patients were included in a voxel-based lesion-symptom mapping (VLSM) analysis to identify deficit related areas (ROI). Then, a ROI group-wise comparison was performed. Additionally, a whole-brain voxel-based-morphometry (VBM) analysis was run, in which healthy participant's REAPPself ability scores were correlated with gray matter intensities. Results showed that (1) regions in the right superior frontal gyrus (SFG), comprising the right dorsolateral prefrontal cortex (BA9) and the right dorsal anterior cingulate cortex (BA32), were associated with patient's impaired down-regulation of arousal, (2) a lesion in the depicted ROI occasioned significant REAPPself impairments, (3) REAPPself ability of controls was linked with increased gray matter intensities in the ROI regions. Our findings show for the first time that the neural integrity and the structural volume of right SFG regions (BA9/32) might be indispensable for REAPPself. Implications for neurofeedback research are discussed.Fil: Falquez, Rosalux. University of Heidelberg; AlemaniaFil: Couto, Juan Blas Marcos. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Neurociencia Cognitiva. Fundación Favaloro. Instituto de Neurociencia Cognitiva; ArgentinaFil: Ibáñez Barassi, Agustín Mariano. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Neurociencia Cognitiva. Fundación Favaloro. Instituto de Neurociencia Cognitiva; ArgentinaFil: Freitag, Martin T.. German Cancer Research Center; AlemaniaFil: Berger, Moritz. German Cancer Research Center; AlemaniaFil: Arens, Elisabeth A.. University of Heidelberg; AlemaniaFil: Lang, Simone. University of Heidelberg; AlemaniaFil: Barnow, Sven. University of Heidelberg; Alemani
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A Nyström method for a class of integral equations on the real line with applications to scattering by diffraction gratings and rough surfaces
We propose a Nystr¨om/product integration method for a class of second kind integral equations on the real line which arise in problems of two-dimensional scalar and elastic wave scattering by unbounded surfaces. Stability and convergence of the method is established with convergence rates dependent on the smoothness of components of the kernel. The method is applied to the problem of acoustic scattering by a sound soft one-dimensional surface which is the graph of a function f, and superalgebraic convergence is established in the case when f is infinitely smooth. Numerical results are presented illustrating this behavior for the case when f is periodic (the diffraction grating case). The Nystr¨om method for this problem is stable and convergent uniformly with respect to the period of the grating, in contrast to standard integral equation methods for diffraction gratings
which fail at a countable set of grating periods
Spin Asymmetries In Diffractive Leptoproduction
In this report we calculate the cross section and asymmetry for the
diffractive leptoproduction. We study dependences of the asymmetry on
the structure of the Pomeron-proton couplingComment: 4 pages, latex, two PS figures, presented at the International
Workshop "Symmetry and Spin" PRAHA'9
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