1,316,158 research outputs found
Luminosity Spectrum Reconstruction at Linear Colliders
A good knowledge of the luminosity spectrum is mandatory for many
measurements at future e+e- colliders. As the beam-parameters determining the
luminosity spectrum cannot be measured precisely, the luminosity spectrum has
to be measured through a gauge process with the detector. The measured
distributions, used to reconstruct the spectrum, depend on Initial State
Radiation, cross-section, and Final State Radiation. To extract the basic
luminosity spectrum, a parametric model of the luminosity spectrum is created,
in this case the spectrum at the 3 TeV Compact Linear Collider (CLIC). The
model is used within a reweighting technique to extract the luminosity spectrum
from measured Bhabha event observables, taking all relevant effects into
account. The centre-of-mass energy spectrum is reconstructed within 5% over the
full validity range of the model. The reconstructed spectrum does not result in
a significant bias or systematic uncertainty in the exemplary physics benchmark
process of smuon pair production.Comment: Version accepted by EPJC. Minor change
The use of the experimentally deduced Brunt-Vaisala frequency and turbulent velocity fluctuations to estimate the eddy diffusion coefficient
The determination of the turbulent energy dissipation rate or the eddy diffusion coefficient from radar observations can be done through the turbulence refractive index structure constant, deduced from calibrated echo power measurements, or through the turbulent velocity fluctuations, deduced from the echo spectrum width. Besides the radar parameters, power and spectrum width, the first approach needs knowledge of profiles of temperature and electron density in the mesosphere and the fraction of the radar volume filled with turbulence. The latter approach needs knowledge of the temperature profile, namely, the Brunt-Vaisala frequency. The use of this latter approach is demonstrated
Quasiclassical Random Matrix Theory
We directly combine ideas of the quasiclassical approximation with random
matrix theory and apply them to the study of the spectrum, in particular to the
two-level correlator. Bogomolny's transfer operator T, quasiclassically an NxN
unitary matrix, is considered to be a random matrix. Rather than rejecting all
knowledge of the system, except for its symmetry, [as with Dyson's circular
unitary ensemble], we choose an ensemble which incorporates the knowledge of
the shortest periodic orbits, the prime quasiclassical information bearing on
the spectrum. The results largely agree with expectations but contain novel
features differing from other recent theories.Comment: 4 pages, RevTex, submitted to Phys. Rev. Lett., permanent e-mail
[email protected]
The photon energy spectrum in B-> X_s + \gamma in perturbative QCD through O(\alpha_s^2)
We derive the dominant part of the O(\alpha_s^2) correction to the photon
energy spectrum in the inclusive decay B-> X_s+gamma. The detailed knowledge of
the spectrum is important for relating the theoretical calculations of the B->
X_s + \gamma decay rate and the experimental measurements where a cut on the
photon energy is applied. In addition, moments of the photon energy spectrum
are used for the determination of the b-quark mass and other fundamental
parameters of heavy quark physics. Our calculation reduces the theoretical
uncertainty associated with uncalculated higher orders effects and shows that,
for B-> X_s+\gamma, QCD radiative corrections to the photon energy spectrum are
under theoretical control.Comment: 8 pages, 6 figures; references adde
Reconstructing the Inflaton Potential---in Principle and in Practice
Generalizing the original work by Hodges and Blumenthal, we outline a
formalism which allows one, in principle, to reconstruct the potential of the
inflaton field from knowledge of the tensor gravitational wave spectrum or the
scalar density fluctuation spectrum, with special emphasis on the importance of
the tensor spectrum. We provide some illustrative examples of such
reconstruction. We then discuss in some detail the question of whether one can
use real observations to carry out this procedure. We conclude that in
practice, a full reconstruction of the functional form of the potential will
not be possible within the foreseeable future. However, with a knowledge of the
dark matter components, it should soon be possible to combine
intermediate-scale data with measurements of large-scale cosmic microwave
background anisotropies to yield useful information regarding the potential.Comment: 39 pages plus 2 figures (upon request:[email protected]), LaTeX,
FNAL--PUB--93/029-A; SUSSEX-AST 93/3-
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