1,675 research outputs found
Dark energy and dark matter from cosmological observations
The present status of our knowledge about the dark matter and dark energy is
reviewed. Bounds on the content of cold and hot dark matter from cosmological
observations are discussed in some detail. I also review current bounds on the
physical properties of dark energy, mainly its equation of state and effective
speed of sound.Comment: 12 pages, 4 figures, to appear in Lepton-Photon 2005 proceedings,
added figure and typos correcte
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QCD and jets at CDF
A summary of QCD results from the Collider Detector at Fermilab is presented. Comparisons are made to leading order, O({alpha}{sub s}{sup 2}), and next-to-leading order, O({alpha}{sub s}{sup 3}), parton level calculations and to leading logarithm shower Monte Carlo results
Direct Search for Low Mass Dark Matter Particles with CCDs
A direct dark matter search is performed using fully-depleted
high-resistivity CCD detectors . Due to their low electronic readout noise (RMS
~ 7 eV) these devices operate with a very low detection threshold of 40 eV,
making the search for dark matter particles with low masses (~ 5 GeV) possible.
The results of an engineering run performed in a shallow underground site are
presented, demonstrating the potential of this technology in the low mass
region
Snowmass 2001: Jet Energy Flow Project
Conventional cone jet algorithms arose from heuristic considerations of LO
hard scattering coupled to independent showering. These algorithms implicitly
assume that the final states of individual events can be mapped onto a unique
set of jets that are in turn associated with a unique set of underlying hard
scattering partons. Thus each final state hadron is assigned to a unique
underlying parton. The Jet Energy Flow (JEF) analysis described here does not
make such assumptions. The final states of individual events are instead
described in terms of flow distributions of hadronic energy. Quantities of
physical interest are constructed from the energy flow distribution summed over
all events. The resulting analysis is less sensitive to higher order
perturbative corrections and the impact of showering and hadronization than the
standard cone algorithms.Comment: REVTeX4, 13 pages, 6 figures; Contribution to the P5 Working Group on
QCD and Strong Interactions at Snowmass 200
Anomalous Chromomagnetic Moments of Quarks and Large Transverse Energy Jets
We consider the jet cross sections for gluons coupling to quarks with an
anomalous chromomagnetic moment. We then apply this to the deviation and bounds
from QCD found in the CDF and D0 Fermilab data, respectively, to find a range
of possible values for the anomalous moments. The quadratic and quartic terms
in the anomalous moments can fit to the rise of a deviation with transverse
energy. Since previous analyses have been done on the top quark total cross
section, here we assume the same moment on all quarks except the top and find
the range TeV for the
CDF data. Assuming the anomalous moment is present only on a charm or bottom
quark which is pair produced results in a range TeV. The magnitudes here are compared with anomalous magnetic moments
that could account for and found to be in the same general range, as well
as not inconsistent with LEP and SLD bounds on .Comment: REVTeX, 11 pages, 2 postscript figure
Summary: Working Group on QCD and Strong Interactions
In this summary of the considerations of the QCD working group at Snowmass
2001, the roles of quantum chromodynamics in the Standard Model and in the
search for new physics are reviewed, with empahsis on frontier areas in the
field. We discuss the importance of, and prospects for, precision QCD in
perturbative and lattice calculations. We describe new ideas in the analysis of
parton distribution functions and jet structure, and review progress in
small- and in polarization.Comment: Snowmass 2001. Revtex4, 34 pages, 4 figures, revised to include
additional references on jets and lattice QC
Snowmass 2001: Jet Energy Flow Project
Conventional cone jet algorithms arose from heuristic considerations of LO hard scattering coupled to independent showering. These algorithms implicitly assume that the final states of individual events can be mapped onto a unique set of jets that are in turn associated with a unique set of underlying hard scattering partons. Thus each final state hadron is assigned to a unique underlying parton. The Jet Energy Flow (JEF) analysis described here does not make such assumptions. The final states of individual events are instead described in terms of flow distributions of hadronic energy. Quantities of physical interest are constructed from the energy flow distribution summed over all events. The resulting analysis is less sensitive to higher order perturbative corrections and the impact of showering and hadronization than the standard cone algorithms
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Measurements of charge diffusion in deep-depletion CCDs by optical diffraction
The charge diffusion is measured in back illuminated, fully depleted, 250 {micro}m thick CCDs by imaging the diffraction pattern of a double slit. The CCDs studied are the focal plane detectors for the Dark Energy Camera (DECam) instrument currently under construction for the Dark Energy Survey (DES). The results presented here indicate that the dispersion of charge due to diffusion can be kept below the DES specification ({sigma}{sub d} < 7.0 {micro}m)
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