4,896 research outputs found

### Existence of compatible contact structures on Gâ -manifolds

In this paper, we show the existence of (co-oriented) contact structures on certain classes of G(2)-manifolds, and that these two structures are compatible in certain ways. Moreover, we prove that any seven-manifold with a spin structure (and so any manifold with G(2)-structure) admits an almost contact structure. We also construct explicit almost contact metric structures on manifolds with G(2)-structures

### Baryonic Resonance Studies with STAR

Yields and spectra of $\Sigma(1385)$ are measured in $p+p$, d+Au and Au+Au
collisions at $\sqrt{s_{NN}}=200$ GeV . The nuclear modification factors in
d+Au collisions are presented. The $p_{T}$ dependent medium effects are
investigated via the nuclear modification factors. The implications of these
results on various models are discussed.Comment: Strange Quark Matter 2006 Conference Talk Proceeding

### Reconstructed Jets at RHIC

To precisely measure jets over a large background such as pile up in high
luminosity p+p collisions at LHC, a new generation of jet reconstruction
algorithms is developed. These algorithms are also applicable to reconstruct
jets in the heavy ion environment where large event multiplicities are
produced. Energy loss in the medium created in heavy ion collisions are already
observed indirectly via inclusive hadron distributions and di-hadron
correlations. Jets can be used to study this energy loss in detail with reduced
biases. We review the latest results on jet-medium interactions as seen in A+A
collisions at RHIC, focusing on the recent progress on jet reconstruction in
heavy ion collisions.Comment: Proceedings for the 26th Winter Workshop on Nuclear Dynamic

### Hadronization Approach for a Quark-Gluon Plasma Formed in Relativistic Heavy Ion Collisions

A transport model is developed to describe hadron emission from a strongly
coupled quark-gluon plasma formed in relativistic heavy ion collisions. The
quark-gluon plasma is controlled by ideal hydrodynamics, and the hadron motion
is characterized by a transport equation with loss and gain terms. The two sets
of equations are coupled to each other, and the hadronization hypersurface is
determined by both the hydrodynamic evolution and the hadron emission. The
model is applied to calculate the transverse momentum distributions of mesons
and baryons, and most of the results agree well with the experimental data at
RHIC.Comment: 16 pages, 24 figures. Version accepted by PR

### Strange hadrons as dense matter probes

The spectra of strange hadrons have been measured in detail as a function of
centrality for a variety of collision systems and energies at RHIC. Recent
results are presented and compared to those measured at the SPS. The effects of
the system size on strange particle production and kinematics are examined. I
place specific emphasis on comparing A-A to pp production and discuss how
strangeness can be used to probe the dense matter produced in heavy-ion
collisions.Comment: Proceedings of the Strange Quark Matter Conference 200

### Resonance production in heavy ion collisions

Recent results of resonance production from RHIC at $\sqrt{s_{\rm NN}} =$
200 GeV and SPS at $\sqrt{s_{\rm NN}} =$ 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 $\Lambda$(1520)/$\Lambda$ ratios suggest a
time between two freeze-outs surfaces of $\Delta \tau>$ 4 fm/c. The difference
in momentum distributions and yields for the $\phi$(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

### Jet Reconstruction in Heavy Ion Collisions

We examine the problem of jet reconstruction at heavy-ion colliders using
jet-area-based background subtraction tools as provided by FastJet. We use
Monte Carlo simulations with and without quenching to study the performance of
several jet algorithms, including the option of filtering, under conditions
corresponding to RHIC and LHC collisions. We find that most standard algorithms
perform well, though the anti-kt and filtered Cambridge/Aachen algorithms have
clear advantages in terms of the reconstructed transverse-momentum offset and
dispersion.Comment: 31 pages, 17 figure

### M-theory moduli spaces and torsion-free structures

Motivated by the description of $\mathcal{N}=1$ M-theory compactifications to
four-dimensions given by Exceptional Generalized Geometry, we propose a way to
geometrize the M-theory fluxes by appropriately relating the compactification
space to a higher-dimensional manifold equipped with a torsion-free structure.
As a non-trivial example of this proposal, we construct a bijection from the
set of $Spin(7)$-structures on an eight-dimensional $S^{1}$-bundle to the set
of $G_{2}$-structures on the base space, fully characterizing the
$G_{2}$-torsion clases when the total space is equipped with a torsion-free
$Spin(7)$-structure. Finally, we elaborate on how the higher-dimensional
manifold and its moduli space of torsion-free structures can be used to obtain
information about the moduli space of M-theory compactifications.Comment: 24 pages. Typos fixed. Minor clarifications adde

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