548 research outputs found
Systematization of tensor mesons and the determination of the glueball
It is shown that new data on the -resonances in the mass
range MeV support the linearity of the -trajectories,
where is the radial quantum number of quark--antiquark state. In this way
all vacancies for the isoscalar tensor -mesons in the range up to 2450
MeV are filled in. This allows one to fix the broad -state with
MeV and MeV as the lowest tensor glueball. PACS
numbers: 14.40.-n, 12.38.-t, 12.39.-MkComment: 10 pages, 1 figur
ATHENA -- First Production of Cold Antihydrogen and Beyond
Atomic systems of antiparticles are the laboratories of choice for tests of
CPT symmetry with antimatter. The ATHENA experiment was the first to report the
production of copious amounts of cold antihydrogen in 2002. This article
reviews some of the insights that have since been gained concerning the
antihydrogen production process as well as the external and internal properties
of the produced anti-atoms. Furthermore, the implications of those results on
future prospects of symmetry tests with antimatter are discussed.Comment: Proc. of the Third Meeting on CPT and Lorentz Symmetry, Bloomington
(Indiana), USA, August 2004, edited by V. A. Kostelecky (World Scientific,
Singapore). 10 pages, 5 figures, 1 table. Author affiliations cor
Cold-Antimatter Physics
The CPT theorem and the Weak Equivalence Principle are foundational
principles on which the standard description of the fundamental interactions is
based. The validity of such basic principles should be tested using the largest
possible sample of physical systems. Cold neutral antimatter (low-energy
antihydrogen atoms) could be a tool for testing the CPT symmetry with high
precision and for a direct measurement of the gravitational acceleration of
antimatter. After several years of experimental efforts, the production of
low-energy antihydrogen through the recombination of antiprotons and positrons
is a well-established experimental reality. An overview of the ATHENA
experiment at CERN will be given and the main experimental results on
antihydrogen formation will be reviewed.Comment: Proceedings of the XLIII International Meeting on Nuclear Physics,
Bormio (Italy), March 13-20 (2005). 10 pages, 4 figures, 1 tabl
Detection of antihydrogen annihilations with a Si-micro-strip and pure CsI detector
In 2002, the ATHENA collaboration reported the creation and detection of cold
(~15 K) antihydrogen atoms [1]. The observation was based on the complete
reconstruction of antihydrogen annihilations, simultaneous and spatially
correlated annihilations of an antiproton and a positron. Annihilation
byproducts are measured with a cylindrically symmetric detector system
consisting of two layers of double sided Si-micro-strip modules that are
surrounded by 16 rows of 12 pure CsI crystals (13 x 17.5 x 17 mm^3). This paper
gives a brief overview of the experiment, the detector system, and event
reconstruction.
Reference 1. M. Amoretti et al., Nature 419, 456 (2002).Comment: 7 pages, 5 figures; Proceedings for the 8th ICATPP Conference on
Astroparticle, Particle, Space Physics, Detectors and Medical Physics
Applications (Como, Italy October 2003) to be published by World Scientific
(style file included
Antihyperlipidemic effects of Pleurotus ostreatus (oyster mushrooms) in HIV-infected individuals taking antiretroviral therapy
<p>Abstract</p> <p>Background</p> <p>Antiretroviral treatment (ART) regimens in HIV patients commonly cause significant lipid elevations, including increases in both triglycerides and cholesterol. Standard treatments for hypercholesterolemia include the HMG CoA reductase inhibitors, or "statins." Because many ART agents and statins share a common metabolic pathway that uses the cytochrome P450 enzyme system, coadministration of ART with statins could increase statin plasma levels significantly. The oyster mushroom, <it>Pleurotus ostreatus</it>, has been shown in animal models to decrease lipid levels - a finding that has been supported by preliminary data in a small human trial.</p> <p>Methods</p> <p>To assess the safety and efficacy of <it>P. ostreatus </it>in patients with HIV and ART-induced hyperlipidemia, a single-arm, open-label, proof-of-concept study of 8 weeks' duration with a target enrollment of 20 subjects was conducted. Study patients with ART-induced elevated non-HDL cholesterol levels (> 160 mg/dL) were enrolled. Participants received packets of freeze-dried <it>P. ostreatus </it>(15 gm/day) to be administered orally for the 8 week trial period. Lipid levels were drawn every two weeks to assess efficacy. Safety assessments included self-reported incidence of muscle aches and measurement of liver and muscle enzymes. Mean within-person change in lipid levels were estimated using generalized estimating equations to account for repeated observations on individuals. A 30 mg/dL decrease in non-HDL cholesterol was deemed clinically significant.</p> <p>Results</p> <p>126 patients were screened to enroll 25, of which 20 completed the 8-week study. The mean age was 46.4 years (36-60). Patients had a mean 13.7 yrs of HIV infection. Mean non-HDL cholesterol was 204.5 mg/dL at day 0 and 200.2 mg/dL at day 56 (mean within-person change = -1.70; 95% confidence interval (CI) = -17.4, 14.0). HDL cholesterol levels increased from 37.8 mg/dL at day 0 to 40.4 mg/dL on day 56 (mean within-person change = 2.6; 95% CI = -0.1, 5.2). Triglycerides dropped from 336.4 mg/dL on day 0 to 273.4 mg/dL on day 56 (mean within-person change = -63.0; 95% CI = -120.9, -5.1). Only 3 individuals achieved a sustained clinically significant (30 mg/dL) decline in non-HDL cholesterol after 8 weeks of therapy. There were no adverse experiences reported other than patients' distaste for the preparation. Liver function tests and muscle enzymes were not affected by the 8 weeks of treatment.</p> <p>Conclusions</p> <p><it>Pleurotus ostreatus </it>as administered in this experiment did not lower non-HDL cholesterol in HIV patients with ART-induced hypercholesterolemia. Small changes in HDL and triglycerides were not of a clinical magnitude to warrant further study.</p> <p>Trial Registration</p> <p>clinicaltrials.gov Identifier: <a href="http://www.clinicaltrials.gov/ct2/show/NCT00069524">NCT00069524</a></p
Measurement of the branching ratios of the Z0 into heavy quarks
We measure the hadronic branching ratios of the Z0 boson into heavy quarks:
Rb=Gamma(Z0->bb)/Gamma(Z0->hadrons) and Rc=Gamma(Z0->cc/Gamma(Z0->hadrons)
using a multi-tag technique. The measurement was performed using about 400,000
hadronic Z0 events recorded in the SLD experiment at SLAC between 1996 and
1998. The small and stable SLC beam spot and the CCD-based vertex detector were
used to reconstruct bottom and charm hadron decay vertices with high efficiency
and purity, which enables us to measure most efficiencies from data. We obtain,
Rb=0.21604 +- 0.00098(stat.) +- 0.00073(syst.) -+ 0.00012(Rc) and, Rc= 0.1744
+- 0.0031(stat.) +- 0.0020(syst.) -+ 0.0006(Rb)Comment: 37 pages, 8 figures, to be submitted to Phys. Rev. D version 2:
changed title to ratios, used common D production fractions for Rb and Rc and
corrected Zgamma interference. Identical to PRD submissio
Search for time-dependent B0s - B0s-bar oscillations using a vertex charge dipole technique
We report a search for B0s - B0s-bar oscillations using a sample of 400,000
hadronic Z0 decays collected by the SLD experiment. The analysis takes
advantage of the electron beam polarization as well as information from the
hemisphere opposite that of the reconstructed B decay to tag the B production
flavor. The excellent resolution provided by the pixel CCD vertex detector is
exploited to cleanly reconstruct both B and cascade D decay vertices, and tag
the B decay flavor from the charge difference between them. We exclude the
following values of the B0s - B0s-bar oscillation frequency: Delta m_s < 4.9
ps-1 and 7.9 < Delta m_s < 10.3 ps-1 at the 95% confidence level.Comment: 18 pages, 3 figures, replaced by version accepted for publication in
Phys.Rev.D; results differ slightly from first versio
Direct Measurements of A_b and A_c using Vertex/Kaon Charge Tags at SLD
Exploiting the manipulation of the SLC electron-beam polarization, we present
precise direct measurements of the parity violation parameters A_c and A_b in
the Z boson - c quark and Z boson - b quark coupling. Quark/antiquark
discrimination is accomplished via a unique algorithm that takes advantage of
the precise SLD CCD vertex detector, employing the net charge of displaced
vertices as well as the charge of kaons that emanate from those vertices. From
the 1996-98 sample of 400,000 Z decays, produced with an average beam
polarization of 73.4%, we find A_c = 0.673 +/- 0.029 (stat.) +/- 0.023 (syst.)
and A_b = 0.919 +/- 0.018 (stat.) +/- 0.017 (syst.).Comment: 11 pages, 2 figures, 2 tables, to be submitted to Physical Review
Letters; version 2 reflects changes suggested by the refere
Development of a detector for inertial sensing of positronium at AEgIS (CERN)
The primary goal of the AEgIS collaboration at CERN is to measure the gravitational acceleration on neutral antimatter. Positronium (Ps), the bound state of an electron and a positron, is a suitable candidate for a force-sensitive inertial measurement by means of deflectometry/interferometry. In order to conduct such an experiment, the impact position and time of arrival of Ps atoms at the detector must be detected simultaneously. The detection of a low-velocity Ps beam with a spatial resolution of (88 ± 5) μm was previously demonstrated [1]. Based on the methodology employed in [1] and [2], a hybrid imaging/timing detector with increased spatial resolution of about 10 μm was developed. The performance of a prototype was tested with a positron beam. The concept of the detector and first results are presented
- …