1,877 research outputs found
QED \otimes QCD Threshold Corrections at the LHC
We use the theory of YFS resummation to compute the size of the expected
resummed soft radiative threshold effects in precision studies of heavy
particle production at the LHC, where accuracies of 1 percent are desired in
some processes. We find that the soft QED threshold effects are at the level of
0.3 percent whereas the soft QCD threshold effects enter at the level of 20
percent and hence both must be controlled to be on the conservative side to
achieve such goals.Comment: 8 pages, no figures; improved text; improved refs. and tex
The Virtual Correction to Bremsstrahlung in High-Energy e+ e- Annihilation: Comparison of Exact Results
We have compared the virtual corrections to single hard bremsstrahlung as
calculated by S. Jadach, M. Melles, B.F.L. Ward and S.A. Yost to several other
expressions. The most recent of these comparisons is to the leptonic tensor
calculated by J.H. Kuhn and G. Rodrigo for radiative return. Agreement is found
to within a part in 10^5 or better, as a fraction of the Born cross section,
for most of the range of photon energies. The massless limits have been shown
to agree analytically to NLL order.Comment: 7 pages, 2 figures. Presented by S.A. Yost at ICHEP 2004,
International Conference on High Energy Physics, Beijing, August 16-22, 200
Extreme Nonlinear Optics in a Femtosecond Enhancement Cavity
Intrinsic to the process of high-order harmonic generation is the creation of
plasma and the resulting spatiotemporal distortions of the driving laser pulse.
Inside a high finesse cavity where the driver pulse and gas medium are reused,
this can lead to optical bistability of the cavity-plasma system, accumulated
self-phase modulation of the intracavity pulse, and coupling to higher order
cavity modes. We present an experimental and theoretical study of these effects
and discuss their implications for power scaling of intracavity high-order
harmonic generation and extreme ultraviolet frequency combs
New Results on Precision Studies of Heavy Vector Boson Physics
We present new results for two important heavy vector boson physics
processes: (1), virtual corrections to hard bremsstrahlung which are relevant
to precision predictions for the radiative return process in Z boson production
at and beyond LEP2 energies ; and, (2), electric charge screening effects in
single W production with finite p_T, multiple photon radiation in high energy
collider physics processes. In both cases we show that we improve the
respective precision tag significantly. Phenomenological implications are
discussed.Comment: 5 pages, 2 figures; to appear in Proc. DPF200
Automatic wheeze detection based on auditory modelling
Automatic wheeze detection has several potential benefits compared with reliance on human auscultation: it is experience independent, an automated historical record can easily be kept, and it allows quantification of wheeze severity. Previous attempts to detect wheezes automatically have had partial success but have not been reliable enough to become widely accepted as a useful tool. In this paper an improved algorithm for automatic wheeze detection based on auditory modelling is developed, called the frequency- and duration-dependent threshold algorithm. The mean frequency and duration of each wheeze component are obtained automatically. The detected wheezes are marked on a spectrogram. In the new algorithm, the concept of a frequency- and duration-dependent threshold for wheeze detection is introduced. Another departure from previous work is that the threshold is based not on global power but on power corresponding to a particular frequency range. The algorithm has been tested on 36 subjects, 11 of whom exhibited characteristics of wheeze. The results show a marked improvement in the accuracy of wheeze detection when compared with previous algorithms
Threshold Corrections in Precision LHC Physics: QED otimes QCD
With an eye toward LHC processes in which theoretical precisions of 1 percent
are desired, we introduce the theory of the simultaneous YFS resummation of QED
and QCD to compute the size of the expected resummed soft radiative threshold
effects in precision studies of heavy particle production at the LHC. Our
results show that both QED and QCD soft threshold effects must be controlled to
be on the conservative side to achieve such precision goals.Comment: 4 pages, no figures; presented by B.F.L. Ward in DPF200
Comparison of Exact Results for the Virtual Corrections to Bremsstrahlung in Electron-Positron Annihilation at High Energies
We have compared the virtual corrections to electron-positron annihilation to
fermion pairs with single hard bremsstrahlung as calculated by S. Jadach, M.
Melles, B.F.L. Ward and S.A. Yost to several other expressions. The most recent
of these comparisons is to the leptonic tensor calculated by J.H. Kuhn and G.
Rodrigo for radiative return. Agreement is found to within or better,
as a fraction of the Born cross section.Comment: 5 pages, 2 figures. Presented at LCWS 2004, International Conference
on Linear Colliders, Paris, April 19-23, 200
Threshold Corrections in QED otimes QCD at the LHC
In some processes at the LHC, theoretical precisions of 1 percent are
desired. With an eye toward such precisions, we introduce the theory of the
simultaneous YFS resummation of QED and QCD to compute the size of the expected
resummed soft radiative threshold effects in precision studies of heavy
particle production at the LHC. Our results, that the soft QED threshold
effects are at the level of 0.3 percent whereas the soft QCD threshold effects
enter at the level of 20 percent, show that both must be controlled to be on
the conservative side to achieve such precision goals.Comment: 4 pages, no figures; presented by B.F.L. Ward at ICHEP0
Ramond-Ramond Central Charges in the Supersymmetry Algebra of the Superstring
The free action for the massless sector of the Type II superstring was
recently constructed using closed RNS superstring field theory. The
supersymmetry transformations of this action are shown to satisfy an N=2 D=10
SUSY algebra with Ramond-Ramond central charges.Comment: 10 pages harvmac te
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