1,543 research outputs found
Tables of Hertzian Contact-Stress Coefficients
Coordinated Science Laboratory was formerly known as Control Systems LaboratoryJoint Services Electronics Program / DAAB-07-67-C-019
A Proposed Test of the Einstein Theory of Gravitation by Means of an Unshielded Orbiting Gyro Using Passive Telemetry
Coordinated Science Laboratory was formerly known as Control Systems LaboratoryJoint Services Electronics Program / DAAB-07-67-C-0199National Aeronautics and Space Administration / NsG-44
- and -hypernuclei
- and -hypernuclei are studied in the quark-meson
coupling (QMC) model. Comparisons are made with the results for
-hypernuclei studied in the same model previously. Although the scalar
and vector potentials felt by the , and in
the corresponding hypernuclei multiplet which has the same baryon numbers are
quite similar, the wave functions obtained, e.g., for state, are
very different. The baryon density distribution in
Pb is much more pushed away from the center than that for
the in Pb due to the Coulomb force. On the contrary,
the baryon density distributions in -hypernuclei are
much larger near the origin than those for the in the corresponding
-hypernuclei due to its heavy mass. It is also found that level
spacing for the single-particle energies is much smaller than that
for the and .Comment: Latex, 14 pages, 4 figures, text was extended, version to appear in
Phys. Rev.
Thermal analysis of production of resonances in relativistic heavy-ion collisions
Production of resonances is considered in the framework of the
single-freeze-out model of ultra-relativistic heavy ion collisions. The
formalism involves the virial expansion, where the probability to form a
resonance in a two-body channel is proportional to the derivative of the
phase-shift with respect to the invariant mass. The thermal model incorporates
longitudinal and transverse flow, as well as kinematic cuts of the STAR
experiment at RHIC. We find that the shape of the pi+ pi- spectral line
qualitatively reproduces the preliminary experimental data when the position of
the rho peak is lowered. This confirms the need to include the medium effects
in the description of the RHIC data. We also analyze the transverse-momentum
spectra of rho, K*(892), and f_0(980), and find that the slopes agree with the
observed values. Predictions are made for eta, eta', omega, phi, Lambda(1520),
and Sigma(1385).Comment: minor modifications, a reference adde
Strange particle production at RHIC in a single-freeze-out model
Strange particle ratios and pT-spectra are calculated in a thermal model with
single freeze-out, previously used successfully to describe non-strange
particle production at RHIC. The model and the recently released data for phi,
Lambda, anti-Lambda, and K*(892) are in very satisfactory agreement, showing
that the thermal approach can be used to describe the strangeness production at
RHIC.Comment: We have added the comparison of the model predictions to the newly
released Lambda and K*(892) pT-spectra from STA
Out-of-equilibrium evolution of quantum fields in the hybrid model with quantum back reaction
The hybrid model with a scalar "inflaton" field coupled to a "Higgs" field
with a broken symmetry potential is one of the promising models for inflation
and (p)reheating after inflation. We consider the nonequilibrium evolution of
the quantum fields of this model with quantum back reaction in the Hartree
approximation, in particular the transition of the Higgs field from the
metastable "false vacuum" to the broken symmetry phase. We have performed the
renormalization of the equations of motion, of the gap equations and of the
energy density, using dimensional regularization. We study the influence of the
back reaction on the evolution of the classical fields and of the quantum
fluctuations. We observe that back reaction plays an important role over a wide
range of parameters. Some implications of our investigation for the preheating
stage after cosmic inflation are presented.Comment: 35 pages, 16 eps figures, revtex4; v2: typos corrected and references
added, accepted for publication in Physical Review
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
Hydrodynamical analysis of hadronic spectra in the 130 GeV/nucleon Au+Au collisions
We study one-particle spectra and a two-particle correlation function in the
130 GeV/nucleon Au+Au collisions at RHIC by making use of a hydrodynamical
model. We calculate the one-particle hadronic spectra and present the first
analysis of Bose-Einstein correlation functions based on the numerical solution
of the hydrodynamical equations which takes both longitudinal and transverse
expansion into account appropriately. The hydrodynamical model provides
excellent agreement with the experimental data in the pseudorapidity and the
transverse momentum spectra of charged hadrons, the rapidity dependence of
anti-proton to proton ratio, and almost consistent result for the pion
Bose-Einstein correlation functions. Our numerical solution with simple
freeze-out picture suggests the formation of the quark-gluon plasma with large
volume and low net-baryon density.Comment: 7 pages, 8 figures, REVTeX4. Numerical results and figures are
correcte
Nonlinear evolution of the momentum dependent condensates in strong interaction: the ``pseudoscalar laser''
We discuss the relaxation of the scalar and pseudoscalar condensates after a
rapid quench from an initial state with fluctuations. If we include not only
the zero-mode but also higher modes of the condensates in the classical
evolution, we observe parametric amplification of those ``hard'' modes. Thus,
they couple nonlinearly to the ``soft'' modes. As a consequence, domains of
coherent pi-field emerge long after the initial spinodal decomposition. The
momentum-space distribution of pions emerging from the decay of that
momentum-dependent condensate is discussed.Comment: 6 Pages, REVTEX, 8 Figures; one reference and one figure adde
Collective flow and two-pion correlations from a relativistic hydrodynamic model with early chemical freeze out
We investigate the effect of early chemical freeze-out on radial flow,
elliptic flow and HBT radii by using a fully three dimensional hydrodynamic
model. When we take account of the early chemical freeze-out, the space-time
evolution of temperature in the hadron phase is considerably different from the
conventional model in which chemical equilibrium is always assumed. As a
result, we find that radial and elliptic flows are suppressed and that the
lifetime and the spatial size of the fluid are reduced. We analyze the p_t
spectrum, the differential elliptic flow, and the HBT radii at the RHIC energy
by using hydrodynamics with chemically non-equilibrium equation of state.Comment: One subsection and two figures adde
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