3,500 research outputs found
Demonstration of Self-Updating Landslide Hazard Maps with Dynamic Crowd-Sourced Data in Rwanda
No abstract availabl
Resonance production in heavy ion collisions
Recent results of resonance production from RHIC at
200 GeV and SPS at 17 GeV are presented and discussed in
terms of the evolution and freeze-out conditions of a hot and dense fireball
medium. Yields and spectra are compared with thermal model predictions at
chemical freeze-out. Deviations in the low transverse momentum region of the
resonance spectrum of the hadronic decay channel, suggest a strongly
interaction hadronic phase between chemical and kinetic freeze-out. Microscopic
models including resonance rescattering and regeneration are able to describe
the trend of the data. The magnitude of the regeneration cross sections for
different inverse decay channels are discussed. Model calculations which
include elastic hadronic interactions between chemical freeze-out and thermal
freeze-out based on the K(892)/K and (1520)/ ratios suggest a
time between two freeze-outs surfaces of 4 fm/c. The difference
in momentum distributions and yields for the (1020) resonance
reconstructed from the leptonic and hadronic decay channels at SPS energy are
discussed taking into account the impact of a hadronic phase and possible
medium modifications.Comment: 8 pages, 4 figures, conference proceedings (SQM2004
What do we learn from Resonance Production in Heavy Ion Collisions?
Resonances with their short life time and strong coupling to the dense and
hot medium are suggested as a signature of the early stage of the fireball
created in a heavy ion collision \cite{rap00,lut01,lut02}. The comparison of
resonances with different lifetimes and quark contents may give information
about time evolution and density and temperature of during the expanding of
fireball medium. Resonances in elementary reactions have been measured since
1960. Resonance production in elementary collisions compared with heavy ion
collisions where we expect to create a hot and dense medium may show the direct
of influence of the medium on the resonances. This paper shows a selection of
the recent resonance measurements from SPS and RHIC heavy ion colliders.Comment: 10 pages, 8 figures, HotQuarks 2004 conference proceeding
What's Interesting About Strangeness Production? - An Overview of Recent Results
In this paper I highlight a few selected topics on strange particle
production in heavy-ion collisions. By studying the yield and spectra of
strange particles we hope to gain understanding of the conditions reached in,
and the ensuing dynamics of, the systems produced when ultra-relativistic
heavy-ions are collided.Comment: 17 Pages, 18 figures, Hot Quarks 2004 Proceeding
The eclipsing X-ray pulsar X-7 in M33
Using our extensive ROSAT X-ray observations of M33, we confirm a 3.45 day
eclipse period for the Einstein source X-7 (Larson & Schulman, 1997) and
discover evidence for a 0.31-s pulse period. The orbital period, pulse period
and observed X-ray luminosity are remarkably similar to SMC X-1. We therefore
suggest M33 X-7 is a neutron star high mass X-ray binary with a 15-40 Msol O/B
companion and a binary separation of 25-33 Rsol if the companion is almost
filling its Roche lobe.Comment: accepted for publication in MNRA
The Off State of GX 339-4
We report BeppoSAX and optical observations of the black hole candidate GX
339-4 during its X-ray `off' state in 1999. The broad-band (0.8-50 keV) X-ray
emission can be fitted by a single power law with spectral index, \alpha ~1.6.
The observed luminosity is 6.6e33 erg s^{-1} in the 0.5-10 keV band, which is
at the higher end of the flux distribution of black hole soft X-ray transients
in quiescence, comparable to that seen in GS 2023+338 and 4U 1630-47. An
optical observation just before the BeppoSAX observation shows the source to be
very faint at these wavelengths as well (B=20.1, V=19.2). By comparing with
previously reported `off' and low states (LS), we conclude that the `off' state
is actually an extension of the LS, i.e. a LS at lower intensities. We propose
that accretion models such as the advection-dominated accretion flows are able
to explain the observed properties in such a state.Comment: Accepted for publication in MNRA
VHMPID: a new detector for the ALICE experiment at LHC
This article presents the basic idea of VHMPID, an upgrade detector for the
ALICE experiment at LHC, CERN. The main goal of this detector is to extend the
particle identification capabilities of ALICE to give more insight into the
evolution of the hot and dense matter created in Pb-Pb collisions. Starting
from the physics motivations and working principles the challenges and current
status of development is detailed.Comment: 4 pages, 6 figures. To be published in EPJ Web of Conference
The HADES Tracking System
The tracking system of the dielectron spectrometer HADES at GSI Darmstadt is
formed out of 24 low-mass, trapezoidal multi-layer drift chambers providing in
total about 30 square meter of active area. Low multiple scattering in the in
total four planes of drift chambers before and after the magnetic field is
ensured by using helium-based gas mixtures and aluminum cathode and field
wires. First in-beam performance results are contrasted with expectations from
simulations. Emphasis is placed on the energy loss information, exploring its
relevance regarding track recognition.Comment: 6 pages, 4 figures, presented at the 10th Vienna Conference on
Instrumentation, Vienna, February 2004, to be published in NIM A (special
issue
A comparison of statistical hadronization models
We investigate the sensitivity of fits of hadron spectra produced in heavy
ion collisions to the choice of statistical hadronization model. We start by
giving an overview of statistical model ambiguities, and what they tell us
about freeze-out dynamics. We then use Montecarlo generated data to determine
sensitivity to model choice. We fit the statistical hadronization models under
consideration to RHIC data, and find that a comparison fits can shed
light on some presently contentious questions.Comment: Proceedings for SQM2003 [7th Int. Conf. on Strangeness in Quark
Matter (Atlantic Beach, NC, USA, Mar 12-17, 2003)], to be published in
Journal of Physics G (Typos corrected, reference added
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