22 research outputs found
Search for R-Parity Violating Decays of Scalar Fermions at LEP
A search for pair-produced scalar fermions under the assumption that R-parity
is not conserved has been performed using data collected with the OPAL detector
at LEP. The data samples analysed correspond to an integrated luminosity of
about 610 pb-1 collected at centre-of-mass energies of sqrt(s) 189-209 GeV. An
important consequence of R-parity violation is that the lightest supersymmetric
particle is expected to be unstable. Searches of R-parity violating decays of
charged sleptons, sneutrinos and squarks have been performed under the
assumptions that the lightest supersymmetric particle decays promptly and that
only one of the R-parity violating couplings is dominant for each of the decay
modes considered. Such processes would yield final states consisting of
leptons, jets, or both with or without missing energy. No significant
single-like excess of events has been observed with respect to the Standard
Model expectations. Limits on the production cross- section of scalar fermions
in R-parity violating scenarios are obtained. Constraints on the supersymmetric
particle masses are also presented in an R-parity violating framework analogous
to the Constrained Minimal Supersymmetric Standard Model.Comment: 51 pages, 24 figures, Submitted to Eur. Phys. J.
Search for the Standard Model Higgs Boson with the OPAL Detector at LEP
This paper summarises the search for the Standard Model Higgs boson in e+e-
collisions at centre-of-mass energies up to 209 GeV performed by the OPAL
Collaboration at LEP. The consistency of the data with the background
hypothesis and various Higgs boson mass hypotheses is examined. No indication
of a signal is found in the data and a lower bound of 112.7GeV/C^2 is obtained
on the mass of the Standard Model Higgs boson at the 95% CL.Comment: 51 pages, 21 figure
Measurement of the Hadronic Photon Structure Function F_2^gamma at LEP2
The hadronic structure function of the photon F_2^gamma is measured as a
function of Bjorken x and of the factorisation scale Q^2 using data taken by
the OPAL detector at LEP. Previous OPAL measurements of the x dependence of
F_2^gamma are extended to an average Q^2 of 767 GeV^2. The Q^2 evolution of
F_2^gamma is studied for average Q^2 between 11.9 and 1051 GeV^2. As predicted
by QCD, the data show positive scaling violations in F_2^gamma. Several
parameterisations of F_2^gamma are in agreement with the measurements whereas
the quark-parton model prediction fails to describe the data.Comment: 4 pages, 2 figures, to appear in the proceedings of Photon 2001,
Ascona, Switzerlan
The Long-Baseline Neutrino Experiment: Exploring Fundamental Symmetries of the Universe
The preponderance of matter over antimatter in the early Universe, the
dynamics of the supernova bursts that produced the heavy elements necessary for
life and whether protons eventually decay --- these mysteries at the forefront
of particle physics and astrophysics are key to understanding the early
evolution of our Universe, its current state and its eventual fate. The
Long-Baseline Neutrino Experiment (LBNE) represents an extensively developed
plan for a world-class experiment dedicated to addressing these questions. LBNE
is conceived around three central components: (1) a new, high-intensity
neutrino source generated from a megawatt-class proton accelerator at Fermi
National Accelerator Laboratory, (2) a near neutrino detector just downstream
of the source, and (3) a massive liquid argon time-projection chamber deployed
as a far detector deep underground at the Sanford Underground Research
Facility. This facility, located at the site of the former Homestake Mine in
Lead, South Dakota, is approximately 1,300 km from the neutrino source at
Fermilab -- a distance (baseline) that delivers optimal sensitivity to neutrino
charge-parity symmetry violation and mass ordering effects. This ambitious yet
cost-effective design incorporates scalability and flexibility and can
accommodate a variety of upgrades and contributions. With its exceptional
combination of experimental configuration, technical capabilities, and
potential for transformative discoveries, LBNE promises to be a vital facility
for the field of particle physics worldwide, providing physicists from around
the globe with opportunities to collaborate in a twenty to thirty year program
of exciting science. In this document we provide a comprehensive overview of
LBNE's scientific objectives, its place in the landscape of neutrino physics
worldwide, the technologies it will incorporate and the capabilities it will
possess.Comment: Major update of previous version. This is the reference document for
LBNE science program and current status. Chapters 1, 3, and 9 provide a
comprehensive overview of LBNE's scientific objectives, its place in the
landscape of neutrino physics worldwide, the technologies it will incorporate
and the capabilities it will possess. 288 pages, 116 figure
Chaotic behaviour in the newton iterative function associated with Kepler's equation
The chaotic behaviour observed when Newton's method is used to solve Kepler's equation is analysed using methods borrowed from chaos theory. The result of the analysis is compared with previous results. A sufficient condition for convergence of a given iterative function is presented and yields ranges of eccentricity and mean anomaly such that Newton's method applied to Kepler's equation will converge from an initial guess of pi
The Vancouver Island fireballs of spring 1998
Three fireballs bright enough to attract the attention of numerous witnesses over Vancouver Island and adjacent areas appeared within an interval of 5 weeks. Each was investigated by in situ interviews of eyewitnesses and instrumental measurement of angles. Although recovery of meteorites is unlikely from any of them, and only two of the investigations yielded credible atmospheric trajectories or ground tracks, it is felt to be useful to place the original measurements on permanent record. In addition, in this paper we advocate the use of a consistent and self-explanatory nomenclature for the geometrical description of the track of a fireball. One of the fireballs was remarkable for the number of independent reports of simultaneous sound described by eyewitnesses, and we feel it is important to place on record the circumstances of events described to us. Although the reality of this often-reported phenomenon is not universally accepted, the body of accumulated anecdotal evidence is by now formidable. However, unambiguous instrumental detection of simultaneous sound has yet to be convincingly achieved
Application of Structure-Based Design and Parallel Chemistry to Identify a Potent, Selective, and Brain Penetrant Phosphodiesterase 2A Inhibitor
Phosphodiesterase 2A (PDE2A) inhibitors
have been reported to demonstrate
in vivo activity in preclinical models of cognition. To more fully
explore the biology of PDE2A inhibition, we sought to identify potent
PDE2A inhibitors with improved brain penetration as compared to current
literature compounds. Applying estimated human dose calculations while
simultaneously leveraging synthetically enabled chemistry and structure-based
drug design has resulted in a highly potent, selective, brain penetrant
compound <b>71</b> (PF-05085727) that effects in vivo biochemical
changes commensurate with PDE2A inhibition along with behavioral and
electrophysiological reversal of the effects of NMDA antagonists in
rodents. This data supports the ability of PDE2A inhibitors to potentiate
NMDA signaling and their further development for clinical cognition
indications
Identification of a Potent, Highly Selective, and Brain Penetrant Phosphodiesterase 2A Inhibitor Clinical Candidate
Computational
modeling was used to direct the synthesis of analogs
of previously reported phosphodiesterase 2A (PDE2A) inhibitor <b>1</b> with an imidazotriazine core to yield compounds of significantly
enhanced potency. The analog PF-05180999 (<b>30</b>) was subsequently
identified as a preclinical candidate targeting cognitive impairment
associated with schizophrenia. Compound <b>30</b> demonstrated
potent binding to PDE2A in brain tissue, dose responsive mouse brain
cGMP increases, and reversal of <i>N</i>-methyl-d-aspartate (NMDA) antagonist-induced (MK-801, ketamine) effects in
electrophysiology and working memory models in rats. Preclinical pharmacokinetics
revealed unbound brain/unbound plasma levels approaching unity and
good oral bioavailability resulting in an average concentration at
steady state (<i>C</i><sub>av,ss</sub>) predicted human
dose of 30 mg once daily (q.d.). Modeling of a modified release formulation
suggested that 25 mg twice daily (b.i.d.) could maintain plasma levels
of <b>30</b> at or above targeted efficacious plasma levels
for 24 h, which became part of the human clinical plan