9,135 research outputs found
Anomalous Multiplicity Fluctuations from Phase Transitions in Heavy Ion Collisions
Event-by-event fluctuations and correlations between particles produced in
relativistic nuclear collisions are studied. The fluctuations in positive,
negative, total and net charge are closely related through correlations. In the
event of a phase transitions to a quark-gluon plasma, fluctuations in total and
net charge can be enhanced and reduced respectively which, however, is very
sensitive to the acceptance and centrality. If the colliding system experiences
strong density fluctuations due, e.g., to droplet formation in a first-order
phase transition, all fluctuations can be enhanced substantially. The
importance of fluctuations and correlations is exemplified by event-by-event
measurement of the multiplicities of 's and charged particles since
these observables should anti-correlate in the presence of co-mover or
anomalous absorption.Comment: revised version to appear in Phys. Rev. C, 5 page
Resonances and fluctuations of strange particle in 200 GeV Au-Au collisions
We perform an analysis of preliminary data on strange particles yields and
fluctuations within the Statistical hadronization model. We begin by describing
the theoretical disagreements between different statistical models currently on
the market. We then show how the simultaneous analysis of yields and
fluctuations can be used to differentiate between the different models, and
determine if one of them can be connected to underlying physics. We perform a
study on a RHIC 200 GeV data sample that includes stable particles, resonances,
and the event-by-event fluctuation of the ratio. We show that the
equilibrium statistical model can not describe the fluctuation, unless an
unrealistically small volume is assumed. Such small volume then makes it
impossible to describe the total particle multiplicity. The non-equilibrium
model,on the other hand, describes both the fluctuation and yields
acceptably due to the extra boost to the fluctuation provided by the high
pion chemical potential. and abundance is described
within error bars, but the is under-predicted to 1.5 standard
deviations. We suggest further measurements that have the potential to test the
non-equilibrium model, as well as gauge the effect of re-interactions between
hadronization and freeze-out.Comment: References added, equations corrected. As accepted for publication by
Journal of Physics
X-ray magnetic circular dichroism characterization of GaN/Ga1-xMnxN digital ferromagnetic heterostructure
We have investigated the magnetic properties of a GaN/Ga1-xMnxN (x = 0.1)
digital ferromagnetic heterostructure (DFH) showing ferromagnetic behavior
using soft x-ray absorption spectroscopy (XAS) and x-ray magnetic circular
dichroism (XMCD). The Mn L2,3-edge XAS spectra were similar to those of
Ga1-xMnxN random alloy thin films, indicating a substitutional doping of high
concentration Mn into GaN. From the XMCD measurements, it was revealed that
paramagnetic and ferromagnetic Mn atoms coexisted in the Ga1-xMnxN digital
layers. The ferromagnetic moment per Mn atom estimated from XMCD agreed well
with that estimated from SQUID measurements. From these results, we conclude
that the ferromagnetic behavior of the GaN/Ga1-xMnxN DFH sample arises only
from substitutional Mn2+ ions in the Ga1-xMnxN digital layers and not from
ferromagnetic precipitates. Subtle differences were also found from the XMCD
spectra between the electronic states of the ferromagnetic and paramagnetic
Mn2+ ions.Comment: 12 pages, 8 figure
{BOAO Photometric Survey of Galactic Open Clusters. II. Physical Parameters of 12 Open Clusters
We have initiated a long-term project, the BOAO photometric survey of open
clusters, to enlarge our understanding of galactic structure using UBVI CCD
photometry of open clusters which have been little studied before. This is the
second paper of the project in which we present the photometry of 12 open
clusters. We have determined the cluster parameters by fitting the Padova
isochrones to the color-magnitude diagrams of the clusters. All the clusters
except for Be 0 and NGC 1348 are found to be intermediate-age to old (0.2 - 4.0
Gyrs) open clusters with a mean metallicity of [Fe/H] = 0.0.Comment: 11 page
Effective theories for real-time correlations in hot plasmas
We discuss the sequence of effective theories needed to understand the
qualitative, and quantitative, behavior of real-time correlators
in ultra-relativistic plasmas. We analyze in detail the case where A is a
gauge-invariant conserved current. This case is of interest because it includes
a correlation recently measured in lattice simulations of classical, hot,
SU(2)-Higgs gauge theory. We find that simple perturbation theory, free kinetic
theory, linearized kinetic theory, and hydrodynamics are all needed to
understand the correlation for different ranges of time. We emphasize how
correlations generically have power-law decays at very large times due to
non-linear couplings to long-lived hydrodynamic modes.Comment: 28 pages, Latex, uses revtex, epsf macro packages [Revised version: t
-> sqrt{t} in a few typos on p. 10.
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