4,066 research outputs found
Hadron Blind Detector for the PHENIX Experiment at RHIC
The PHENIX collaboration has designed a conceptually new Hadron Blind
Detector (HBD) for electron identification in high density hadron environment.
The HBD will identify low momentum electron-positron pairs to reduce the
combinatorial background in the mass region below 1 GeV/c^2. The HBD shall be
installed in PHENIX during the 2007 physics run. The HBD is a windowless
proximity focusing Cherenkov detector with a radiator length of 50 cm, CsI
photocathode and three layers of Gas Electron Multipliers (GEM) for gas
amplification. Pure CF_4 serves both as a radiator and as a detector gas. The
radiation budget of the device is less than 3% of a radiation length.Comment: 4 page
Using the Balance Function to study the charge correlations of hadrons
We present the recent Balance Function (BF) results obtained by the NA49
collaboration for the pseudo-rapidity dependence of non-identified charged
particle correlations for two SPS energies. Experimental results indicate a
clear centrality dependence only in the mid-rapidity region. The results of an
energy dependence study of the BF throughout the whole SPS energy range will
also be discussed. In addition, the correlation of identified hadrons is
studied and presented for the first time. The study of hadron correlation has
also been extended in order to cope with the high multiplicity environment that
is expected to be seen at LHC. We will present the latest results from
simulations concerning the extension of these studies to the ALICE experiment.Comment: To appear in the proccedings of the "Quark Confinement and Hadron
Spectrum VII" conferenc
Multiplicity and mean transverse momentum fluctuations in Au + Au collisions at RHIC
Strong modification of event-by-event fluctuations in global observables was
proposed by several authors as an indicator of the phase transition in system
evolution. We report the results of the analysis of STAR TPC data on the
charged multiplicity and mean transverse momentum fluctuations in Au+Au
collisions at =130 GeV. We discuss the centrality dependence of
the observed fluctuations and compare the results with available data from
lower collision energies and ISR data.Comment: Talk at the International Nuclear Physics Conference INPC2001,
Berkeley, CA, July 29th - August 3rd 200
IRSF/SIRIUS JHKs near-infrared variable star survey in the Magellanic Clouds
We carried out a NIR variable star survey toward the Large and Small
Magellanic Clouds using the InfraRed Survey Facility (IRSF) at Sutherland,
South African Astronomical Observatory. This survey project was initiated in
Dember 2000, and since then, we kept monitoring a total area of 3 square
degrees along the LMC bar and also an area of 1 square degree around the center
of the SMC, sufficiently large to do statistical analysis and to make complete
catalog of variable red giants in the Magellanic Clouds. The detection limits
(S/N=10) of the survey are 17.0, 16.5 and 15.5 at J, H and Ks, respectively. In
this article, we present some results on infrared variables that are not
detected by the previous optical surveys. We show that they do not fall on the
standard period-Ks magnitude relation for Mira-type variables pulsating in the
fundamental mode.Comment: 3 pages, 2 figures. To appear in "Stellar Pulsation: Challenges for
Theory and Observation", Eds. J. Guzik and P. Bradle
Multi-wavelength Observations of LS I +61 303 with VERITAS, Swift and RXT E: 2006-2008
A long term, multi-wavelength monitoring campaign on the TeV binary LS I +61
303 has been performed utilizing >300 GeV observations with VERITAS along with
monitoring in the 0.2-10 keV band by RXTE and Swift between September 2006 and
February 2008. The source was detected by VERITAS as a variable TeV source with
flux values ranging from 5-20% of the Crab Nebula flux with the strongest flux
levels appearing around apastron. X-ray observations by RXTE and Swift show the
source as a highly variable hard X-ray source with flux values varying in the
range of 0.5-3*10^-11 ergs cm^-2 s^-1 over a single orbital cycle. The
2007-2008 RXTE data set also shows the presence of several extremely large
flaring episodes presenting a flux of up to 7.2*10^-11 ergs cm^-2 s^-1, the
largest such flare recorded from this source. Comparison of the contemporaneous
TeV and X-ray data does not show a correlation at this time, however, the
sparsity of data sets do not preclude the existence of such a correlation.Comment: Submitted to Proceedings of "4th Heidelberg International Symposium
on High Energy Gamma-Ray Astronomy 2008
Results of MAGIC on Galactic sources
MAGIC is a single-dish Cherenkov telescope located on La Palma (Spain), hence
with an optimal view on the Northern sky. Sensitive in the 30 GeV-30 TeV energy
band, it is nowadays the only ground-based instrument being able to measure
high-energy gamma-rays below 100 GeV. We review the most recent experimental
results on Galactic sources obtained using MAGIC. These include pulsars, binary
systems, supernova remnants and unidentified sources.Comment: 4 pages, 8 figures, to appear in the proceedings of "4th Heidelberg
International Symposium on High Energy Gamma-Ray Astronomy 2008
Results of MAGIC on Galactic sources
MAGIC is a single-dish Cherenkov telescope located on La Palma (Spain), hence
with an optimal view on the Northern sky. Sensitive in the 30 GeV-30 TeV energy
band, it is nowadays the only ground-based instrument being able to measure
high-energy gamma-rays below 100 GeV. We review the most recent experimental
results on Galactic sources obtained using MAGIC. These include pulsars, binary
systems, supernova remnants and unidentified sources.Comment: 4 pages, 8 figures, to appear in the proceedings of "4th Heidelberg
International Symposium on High Energy Gamma-Ray Astronomy 2008
Scientific Highlights from Observations of Active Galactic Nuclei with the MAGIC Telescope
Since 2004, the MAGIC gamma-ray telescope has newly discovered 6 TeV blazars.
The total set of 13 MAGIC-detected active galactic nuclei includes well-studied
objects at other wavelengths like Markarian 501 and the giant radio galaxy M87,
but also the distant the flat-spectrum radio quasar 3C 279, and the newly
discovered TeV gamma-ray emitter S5 0716+71. In addition, also long-term and
multi-wavelength studies on well-known TeV blazars and systematic searches for
new TeV blazars have been carried out. Here we report selected highlights from
recent MAGIC observations of extragalactic TeV gamma-ray sources, emphasizing
the new physics insights MAGIC was able to contribute.Comment: 4 pages, 2 figures, submitted to proceedings of "4th Heidelberg
International Symposium on High Energy Gamma-Ray Astronomy 2008
Observation of Galactic Gamma-ray Sources with VERITAS
We report on VERITAS observations at energies above 200 GeV of known or
potential galactic gamma-ray sources. The observed objects comprise pulsars,
pulsar wind nebulae, high-mass X-ray binaries and gamma-ray sources with
unknown counterparts in other wavelengths. Among the highlights are the
observation of variable gamma-ray emission from the X-ray binary LS I +61 303
and the detection of MGRO J1906+06/HESS J1906+063, an extended gamma-ray source
which could not be associated with any obvious counterpart at lower energies.Comment: Fixed typos in source name
HD66051: the first eclipsing binary hosting an early-type magnetic star
Early-type magnetic stars are rarely found in close binary systems. No such
objects were known in eclipsing binaries prior to this study. Here we
investigated the eclipsing, spectroscopic double-lined binary HD66051, which
exhibits out-of-eclipse photometric variations suggestive of surface brightness
inhomogeneities typical of early-type magnetic stars. Using a new set of
high-resolution spectropolarimetric observations, we discovered a weak magnetic
field on the primary and found intrinsic, element-dependent variability in its
spectral lines. The magnetic field structure of the primary is dominated by a
nearly axisymmetric dipolar component with a polar field strength G and an inclination with respect to the rotation axis of
. A weaker quadrupolar component is also likely to be
present. We combined the radial velocity measurements derived from our spectra
with archival optical photometry to determine fundamental masses (3.16 and 1.75
) and radii (2.78 and 1.39 ) with a 1-3% precision. We also
obtained a refined estimate of the effective temperatures (13000 and 9000 K)
and studied chemical abundances for both components with the help of
disentangled spectra. We demonstrate that the primary component of HD66051 is a
typical late-B magnetic chemically peculiar star with a non-uniform surface
chemical abundance distribution. It is not an HgMn-type star as suggested by
recent studies. The secondary is a metallic-line star showing neither a strong,
global magnetic field nor intrinsic spectral variability. Fundamental
parameters provided by our work for this interesting system open unique
possibilities for probing interior structure, studying atomic diffusion, and
constraining binary star evolution.Comment: 14 pages, 15 figures; accepted for publication in MNRA
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