7,613 research outputs found
Time-dependent Internal DFT formalism and Kohn-Sham scheme
We generalize to the time-dependent case the stationary Internal DFT /
Kohn-Sham formalism presented in Ref. [14]. We prove that, in the
time-dependent case, the internal properties of a self-bound system (as an
atomic nuclei) are all defined by the internal one-body density and the initial
state. We set-up a time-dependent Internal Kohn-Sham scheme as a practical way
to compute the internal density. The main difference with the traditional DFT /
Kohn-Sham formalism is the inclusion of the center-of-mass correlations in the
functional.Comment: 13 pages. To be published in Phys. Rev.
Modelling the many-body dynamics of heavy ion collisions: Present status and future perspective
Basic problems of the semiclassical microscopic modelling of strongly
interactingsystems are discussed within the framework of Quantum Molecular
Dynamics (QMD). This model allows to study the influence of several types of
nucleonic interactions on a large variety of observables and phenomena
occurring in heavy ion collisions at relativistic energies.It is shown that the
same predictions can be obtained with several -- numerically completely
different and independently written -- programs as far as the same model
parameters are employed and the same basic approximations are made. Many
observables are robust against variations of the details of the model
assumptions used. Some of the physical results, however, depend also on rather
technical parameters like the preparation of the initial configuration in phase
space. This crucial problem is connected with the description of the ground
state of single nuclei,which differs among the various approaches. An outlook
to an improved molecular dynamics scheme for heavy ion collisions is given.Comment: 39 pages, 12 figure
Probing Hadronization with Strangeness
The Omega-bar/Omega ratio originating from string decays is predicted to be
larger than unity in proton-proton interaction at SPS energies. The anti-omega
dominance increases with decreasing beam energy. This surprising behavior is
caused by the combinatorics of quark-antiquark production in small and low-mass
strings. Since this behavior is not found in a statistical description of
hadron production in proton-proton collisions, it may serve as a key observable
to probe the hadronization mechanism in such collisions.Comment: 10 pages, proceedings of the 18th International Winter Workshop on
Nuclear Dynamics, Nassau, Bahamas, January 200
Analysis of reaction dynamics at RHIC in a combined parton/hadron transport approach
We introduce a transport approach which combines partonic and hadronic
degrees of freedom on an equal footing and discuss the resulting reaction
dynamics. The initial parton dynamics is modeled in the framework of the parton
cascade model, hadronization is performed via a cluster hadronization model and
configuration space coalescence, and the hadronic phase is described by a
microscopic hadronic transport approach. The resulting reaction dynamics
indicates a strong influence of hadronic rescattering on the space-time pattern
of hadronic freeze-out and on the shape of transverse mass spectra. Freeze-out
times and transverse radii increase by factors of 2 - 3 depending on the hadron
species.Comment: 10 pages, 4 eps figures include
Effects of a multi-component exercise program and calcium–vitamin-D3-fortified milk on bone mineral density in older men : a randomised controlled trial
Summary We examined the independent and combined effects of a multi-component exercise program and calcium–vitamin-D3-fortified milk on bone mineral density (BMD) in older men. Exercise resulted in a 1.8% net gain in femoral neck BMD, but additional calcium–vitamin D3 did not enhance the response in this group of older well-nourished men.Introduction This 12-month randomised controlled trial assessed whether calcium–vitamin-D3-fortified milk could enhance the effects of a multi-component exercise program on BMD in older men.Methods Men (n  = 180) aged 50–79 years were randomised into: (1) exercise + fortified milk; (2) exercise; (3) fortified milk; or (4) controls. Exercise consisted of high intensity progressive resistance training with weight-bearing impact exercise. Men assigned to fortified milk consumed 400 mL/day of low fat milk providing an additional 1,000 mg/day calcium and 800 IU/day vitamin D3. Femoral neck (FN), total hip, lumbar spine and trochanter BMD and body composition (DXA), muscle strength 25-hydroxyvitamin D and parathyroid hormone (PTH) were assessed.Results There were no exercise-by-fortified milk interactions at any skeletal site. Exercise resulted in a 1.8% net gain in FN BMD relative to no-exercise (p < 0.001); lean mass (0.6 kg, p < 0.05) and muscle strength (20–52%, p < 0.001) also increased in response to exercise. For lumbar spine BMD, there was a net 1.4–1.5% increase in all treatment groups relative to controls (all p < 0.01). There were no main effects of fortified milk at any skeletal site.Conclusion A multi-component community-based exercise program was effective for increasing FN BMD in older men, but additional calcium–vitamin D3 did not enhance the osteogenic response.<br /
Hadronization in heavy ion collisions: Recombination and fragmentation of partons
We argue that the emission of hadrons with transverse momentum up to about 5
GeV/c in central relativistic heavy ion collisions is dominated by
recombination, rather than fragmentation of partons. This mechanism provides a
natural explanation for the observed constant baryon-to-meson ratio of about
one and the apparent lack of a nuclear suppression of the baryon yield in this
momentum range. Fragmentation becomes dominant at higher transverse momentum,
but the transition point is delayed by the energy loss of fast partons in dense
matter.Comment: 4 pages, 2 figures; v2: reference [8] added; v3: Eq.(2) corrected,
two references added, version to appear in PR
Hadronic freeze-out following a first order hadronization phase transition in ultrarelativistic heavy-ion collisions
We analyze the hadronic freeze-out in ultra-relativistic heavy ion collisions
at RHIC in a transport approach which combines hydrodynamics for the early,
dense, deconfined stage of the reaction with a microscopic non-equilibrium
model for the later hadronic stage at which the hydrodynamic equilibrium
assumptions are not valid. With this ansatz we are able to self-consistently
calculate the freeze-out of the system and determine space-time hypersurfaces
for individual hadron species. The space-time domains of the freeze-out for
several hadron species are found to be actually four-dimensional, and differ
drastically for the individual hadrons species. Freeze-out radii distributions
are similar in width for most hadron species, even though the Omega-baryon is
found to be emitted rather close to the phase boundary and shows the smallest
freeze-out radii and times among all baryon species. The total lifetime of the
system does not change by more than 10% when going from SPS to RHIC energies.Comment: 11 pages, 4 eps-figures included, revised versio
Angular hadron correlations probing the early medium evolution
Hard processes are a well calibrated probe to study heavy-ion collisions.
However, the information to be gained from the nuclear suppression factor R_AA
is limited, hene one has to study more differential observables to do medium
tomography. The angular correlations of hadrons associated with a hard trigger
appear suitable as they show a rich pattern when going from low p_T to high
p_T. Of prime interest is the fate of away side partons with an in-medium
pathlength O(several fm). At high p_T the correlations become dominated by the
punchtrough of the away side parton with subsequent fragmentation. We discuss
what information about the medium density can be gained from the data.Comment: Talk given at the 19th International Conference on Ultrarelativistic
Nucleus-Nucleus Collisions: Quark Matter 2006 (QM 2006), Shanghai, China,
14-20 Nov 200
- …