4,006 research outputs found
Jet-fluid string formation and decay in high-energy heavy-ion collisions
We propose a new hadronization mechanism, jet-fluid string (JFS) formation
and decay, to understand observables in intermediate to high- regions
comprehensively. In the JFS model, hard partons produced in jet lose their
energy in traversing the QGP fluid, which is described by fully
three-dimensional hydrodynamic simulations. When a jet parton escapes from the
QGP fluid, it picks up a partner parton from a fluid and forms a color singlet
string, then it decays to hadrons. We find that high- values in JFS
are about two times larger than in the independent fragmentation model.Comment: 6 pages, 2 figures; Proceeding for poster sessions at Quark Matter
2006, Shanghai, China, 14-20 November 2006; to appear in Int. J. of Mod.
Phys.
Indication of intrinsic spin Hall effect in 4d and 5d transition metals
We have investigated spin Hall effects in 4 and 5 transition metals,
Nb, Ta, Mo, Pd and Pt, by incorporating the spin absorption method in the
lateral spin valve structure; where large spin current preferably relaxes into
the transition metals, exhibiting strong spin-orbit interactions. Thereby
nonlocal spin valve measurements enable us to evaluate their spin Hall
conductivities. The sign of the spin Hall conductivity changes systematically
depending on the number of electrons. This tendency is in good agreement
with the recent theoretical calculation based on the intrinsic spin Hall
effect.Comment: 5 pages, 4 figure
Search for a Ridge Structure Origin with Shower Broadening and Jet Quenching
We investigate the role of jet and shower parton broadening by the strong
colour field in the - correlation of high
particles. When anisotropic momentum broadening () is
given to jet and shower partons in the initial stage, a ridge-like structure is
found to appear in the two hadron correlation. The ratio of the peak to the
pedestal yield is overestimated.Comment: Talk given at 20th Int. Conf. on Ultra-Relativistic Nucleus-Nucleus
Collisions, Jaipur, India, Feb.4-10, 200
Explosions inside Ejecta and Most Luminous Supernovae
The extremely luminous supernova SN2006gy is explained in the same way as
other SNIIn events: light is produced by a radiative shock propagating in a
dense circumstellar envelope formed by a previous weak explosion. The problems
in the theory and observations of multiple-explosion SNe IIn are briefly
reviewed.Comment: 9 pages, 6 figures, LateX aipproc.cls. A bit more details and color
added to Fig.3. The 10th International Symposium on Origin of Matter and
Evolution of Galaxies (OMEG07), Sapporo, Japan, December 200
Recent Efforts in Data Compilations for Nuclear Astrophysics
Some recent efforts in compiling data for astrophysical purposes are
introduced, which were discussed during a JINA-CARINA Collaboration meeting on
"Nuclear Physics Data Compilation for Nucleosynthesis Modeling" held at the
ECT* in Trento/ Italy from May 29th- June 3rd, 2007. The main goal of this
collaboration is to develop an updated and unified nuclear reaction database
for modeling a wide variety of stellar nucleosynthesis scenarios. Presently a
large number of different reaction libraries (REACLIB) are used by the
astrophysics community. The "JINA Reaclib Database" on
http://www.nscl.msu.edu/\~nero/db/ aims to merge and fit the latest
experimental stellar cross sections and reaction rate data of various
compilations, e.g. NACRE and its extension for Big Bang nucleosynthesis,
Caughlan and Fowler, Iliadis et al., and KADoNiS. The KADoNiS (Karlsruhe
Astrophysical Database of Nucleosynthesis in Stars,
http://nuclear-astrophysics.fzk.de/kadonis) project is an online database for
neutron capture cross sections relevant to the s process. The present version
v0.2 is already included in a REACLIB file from Basel university
(http://download.nucastro.org/astro/reaclib). The present status of
experimental stellar cross sections in KADoNiS is shown. A "high
priority list" for measurements and evaluations for light charged-particle
reactions set up by the JINA-CARINA collaboration is presented. The central web
access point to submit and evaluate new data is provided by the Oak Ridge group
via the http://www.nucastrodata.org homepage. "Workflow tools" aim to make the
evaluation process transparent and allow users to follow the progress.Comment: Proceedings 10th Int. Symp. on Origin of Matter and Evolution of
Galaxies OMEG07, Sapporo/ Japan, December 4-7 200
The Dichotomy of the Halo of the Milky Way
We summarize evidence that the halo of the Milky Way comprises two different,
and broadly overlapping, stellar components. The two structures exhibit
different chemical compositions, spatial distributions, and kinematics. These
results were obtained through an analysis of more than 20,000 calibration stars
from the Sloan Digital Sky Survey (SDSS). The duality of the stellar halo
directly impacts galaxy formation models, for the Milky Way and other large
spirals.Comment: 6 pages, 4 figures, to appear in Proceedings of the OMEG07
Conference, held in December 200
The r-Process in Supersonic Neutrino-Driven Winds: The Roll of Wind Termination Shock
Recent hydrodynamic studies of core-collapse supernovae imply that the
neutrino-heated ejecta from a nascent neutron star develops to supersonic
outflows. These supersonic winds are influenced by the reverse shock from the
preceding supernova ejecta, forming the wind termination shock. We investigate
the effects of the termination shock in neutrino-driven winds and its roll on
the r-process. Supersonic outflows are calculated with a semi-analytic
neutrino-driven wind model. Subsequent termination-shocked, subsonic outflows
are obtained by applying the Rankine-Hugoniot relations. We find a couple of
effects that can be relevant for the r-process. First is the sudden slowdown of
the temperature decrease by the wind termination. Second is the entropy jump by
termination-shock heating, up to several 100NAk. Nucleosynthesis calculations
in the obtained winds are performed to examine these effects on the r-process.
We find that 1) the slowdown of the temperature decrease plays a decisive roll
to determine the r-process abundance curves. This is due to the strong
dependences of the nucleosynthetic path on the temperature during the r-process
freezeout phase. Our results suggest that only the termination-shocked winds
with relatively small shock radii (~500km) are relevant for the bulk of the
solar r-process abundances (A~100-180). The heaviest part in the solar
r-process curve (A~180-200), however, can be reproduced both in shocked and
unshocked winds. These results may help to constrain the mass range of
supernova progenitors relevant for the r-process. We find, on the other hand,
2) negligible roles of the entropy jump on the r-process. This is a consequence
that the sizable entropy increase takes place only at a large shock radius
(~10,000km) where the r-process has already ceased.Comment: 11 pages, 7 figures, submitted to ApJ, revised following referee's
comments,Accepted for publication in Ap
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