2,487 research outputs found
Prospects of a Search for Neutral, Long-Lived Particles using Photon Timing at CDF
We present the prospects of searches for neutral, long-lived particles which
decay to photons using their time of arrival measured with a newly installed
EMTiming system at CDF. Using GMSB
models we estimate the expected 95% confidence level exclusion regions as a
function of the neutralino mass and lifetime. We find that a combination of
single photon and diphoton analyses should allow the Tevatron in run II to
easily extend the exclusion regions from ALEPH at LEP II, and cover parts of
the theoretically favored < few keV/c^2 GMSB parameter space.Comment: 3 pages, 3 figures; Proceedings for the DPF2004 Conferenc
On the Forward-Backward Asymmetry of Leptonic Decays of at the Fermilab Tevatron
We report on a study of the measurement techniques used to determine the
leptonic forward-backward asymmetry of top anti-top quark pairs in Tevatron
experiments with a proton anti-proton initial state. Recently it was shown that
a fit of the differential asymmetry as a function of (where
is the charge of the lepton from the cascade decay of the top quarks
and is the final pseudorapidity of the lepton in the detector frame)
to a hyperbolic tangent function can be used to extrapolate to the full
leptonic asymmetry. We find this empirical method to well reproduce the results
from current experiments, and present arguments as to why this is the case. We
also introduce two more models, based on Gaussian functions, that better model
the distribution. With our better understanding, we find that
the asymmetry is mainly determined by the shift of the mean of the
distribution, the main contribution to the inclusive asymmetry
comes from the region around , and the extrapolation from
the detector-covered region to the inclusive asymmetry is stable via a
multiplicative scale factor, giving us confidence in the previously reported
experimental results.Comment: 26 pages, 12 figure
Role of Calcium Oxalate Monohydrate Crystal Interactions with Renal Epithelial Cells in the Pathogenesis of Nephrolithiasis: A Review
Renal tubular fluid in the distal nephron is supersaturated with calcium and oxalate ions that nucleate to form crystals of calcium oxalate monohydrate (COM), the most common crystal in renal stones. How these nascent crystals are retained in the nephron to form calculi in certain individuals is not known. Recent studies from this laboratory have demonstrated that COM crystals can bind within seconds to the apical surface of renal epithelial cells, suggesting one mechanism whereby crystals could be retained in the tubule. Adherence of crystals to cells along the nephron may be opposed by specific urinary anions such as glycosaminoglycans, uropontin, nephrocalcin, and citrate. In culture, adherent crystals are quickly internalized by renal cells, and reorganization of the cytoskeleton, alterations in gene expression, and initiation of proliferation can ensue. Each of these cellular events appears to be regulated by extra-cellular factors. Identification of molecules in tubular fluid and on the cell surface that determine whether a crystal-cell interaction results in retention of the crystal or its passage out of the nephron appears critical for understanding the pathogenesis of nephrolithiasis
Long-Lived Neutralino NLSPs
We investigate the collider signatures of heavy, long-lived, neutral
particles that decay to charged particles plus missing energy. Specifically, we
focus on the case of a neutralino NLSP decaying to Z and gravitino within the
context of General Gauge Mediation. We show that a combination of searches
using the inner detector and the muon spectrometer yields a wide range of
potential early LHC discoveries for NLSP lifetimes ranging from 10^(-1)-10^5
mm. We further show that events from Z(l+l-) can be used for detailed kinematic
reconstruction, leading to accurate determinations of the neutralino mass and
lifetime. In particular, we examine the prospects for detailed event study at
ATLAS using the ECAL (making use of its timing and pointing capabilities)
together with the TRT, or using the muon spectrometer alone. Finally, we also
demonstrate that there is a region in parameter space where the Tevatron could
potentially discover new physics in the delayed Z(l+l-)+MET channel. While our
discussion centers on gauge mediation, many of the results apply to any
scenario with a long-lived neutral particle decaying to charged particles.Comment: 31 pages, 12 figure
Prospects for Searching for Excited Leptons during RunII of the Fermilab Tevatron
This letter presents a study of prospects of searching for excited leptons
during RunII of the Fermilab Tevatron. We concentrate on single and pair
production of excited electrons in the photonic decay channel in one CDF/DO
detector equivalent for 2 fb^{-1}. By the end of RunIIa, the limits should be
easily extended beyond those set by LEP and HERA for excited leptons with mass
above about 190 GeV.Comment: 4 pages, 8 figure
The CDF Calorimetry Upgrade for Run IIb
The physics program at the Fermilab Tevatron Collider will continue to
explore the high energy frontier of particle physics until the commissioning of
the LHC at CERN. The luminosity increase provided by the Main Injector will
require upgrades beyond those implemented for the first stage (Run IIa) of the
Tevatron's Run II physics program. The upgrade of the CDF calorimetry includes:
1) the replacement of the slow gas detectors on the front face of the Central
Calorimeter with a faster scintillator version which has a better segmentation,
and 2) the addition of timing information to both the Central and EndPlug
Electromagnetic Calorimeters to filter out cosmic ray and beam related
backgrounds.Comment: Presented at `Frontier Detectors for Frontier Physics; 9th Pisa
Meeting on Advanced Detectors', Biodola, Italy, 25-31 May 2003. 2 page
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