2,667 research outputs found
Strange particle production in a single-freeze-out model
The transverse-momentum spectra and elliptic flow of strange particles are
calculated in the framework of the single-freeze-out model and compared with
the recent RHIC data. An overall very good agreement between the model
predictions and the data is obtained.Comment: talk presented by WF during the VIIIth Int. Conf. on Strangeness in
Quark Matter, Cape Town, Sept. 15-20, 200
Collective inertia and fission barriers within the Skyrme-Hartree-Fock theory
Spontaneous fission barriers, quadrupole inertia, and zero-point
quadrupole-energy corrections are calculated for 252,256,258Fm in the framework
of the self-consistent Skyrme-Hartree-Fock+BCS theory. Two ways of computing
dynamical inertia are employed: the Gaussian Overlap Approximation to the
Generator Coordinate Method and cranking ansatz. The Skyrme results are
compared with those of the Gogny-Hartree-Fock-Bogolyubov model.Comment: 9 pages, 6 figures, missing factor of 2 found, figures corrected, to
be published in International Journal of Modern Physics
Title: Quadrupole collective inertia in nuclear fission: cranking approximation
Collective mass tensor derived from the cranking approximation to the
adiabatic time-dependent Hartree-Fock-Bogoliubov (ATDHFB) approach is compared
with that obtained in the Gaussian Overlap Approximation (GOA) to the generator
coordinate method. Illustrative calculations are carried out for
one-dimensional quadrupole fission pathways in 256Fm. It is shown that the
collective mass exhibits strong variations with the quadrupole collective
coordinate. These variations are related to the changes in the intrinsic shell
structure. The differences between collective inertia obtained in cranking and
perturbative cranking approximations to ATDHFB, and within GOA, are discussed.Comment: 9 pages, RevTeX, 4 figure
Multicolour photometry of Balloon 090100001: linking the two classes of pulsating hot subdwarfs
We present results of the multicolour UBVR photometry of the high-amplitude
EC14026-type star, Balloon 090100001. The data span over a month and consist of
more than a hundred hours of observations. Fourier analysis of these data led
us to the detection of at least 30 modes of pulsation of which 22 are
independent. The frequencies of 13 detected modes group in three narrow ranges,
around 2.8, 3.8 and 4.7 mHz, where the radial fundamental mode, the first and
second overtones are likely to occur. Surprisingly, we also detect 9
independent modes in the low-frequency domain, between 0.15 and 0.4 mHz. These
modes are typical for pulsations found in PG1716+426-type stars, discovered
recently among cool B-type subdwarfs. The modes found in these stars are
attributed to the high-order g modes. As both kinds of pulsations are observed
in Balloon 090100001, it represents a link between the two classes of pulsating
hot subdwarfs. At present, it is probably the most suitable target for testing
evolutionary scenarios and internal constitution models of these stars by means
of asteroseismology.
Three of the modes we discovered form an equidistant frequency triplet which
can be explained by invoking rotational splitting of an = 1 mode. The
splitting amounts to about 1.58 Hz, leading to a rotation period of 7.1
0.1 days.Comment: 12 pages, 14 figures, accepted for publication in MNRAS. For
full-resolution postscript file, visit
http://www.as.wsp.krakow.pl/~andy/balloon.ps.g
Centrality dependence of global variables in relativistic heavy ion collisions: Final data analysis in the framework of a statistical model
The global variables like the transverse energy at midrapidity, the charged
particle multiplicity at midrapidity and the total multiplicity of charged
particles are evaluated in the single-freeze-out statistical model for
different centrality bins at RHIC at and 200 GeV. Full
description of decays of hadron resonances is applied in these estimations. The
geometric parameters of the model are obtained from the fit to the final data
on the spectra. The predicted values of the global variables agree
qualitatively well with the experimental data. The centrality independence of
the total number of charged particles per participant pair has been also
reproduced.Comment: Revtex, 12 figures (included), 16 pages. This is the revised final
version accepted for publication in Physical Review C. The main difference
with the first version is that the geometric parameters of the model have
been fitted again with the use of the newer estimates of the statistical
parameters reported in Refs. [20,21] for the case of GeV.
Also because of the editorial reasons the title has been slightly change
Development of a miniature solid propellant rocket motor for use in plume simulation studies
A miniature solid propellant rocket motor has been developed to be used in a program to determine those parameters which must be duplicated in a cold gas flow to produce aerodynamic effects on an experimental model similar to those produced by hot, particle-laden exhaust plumes. Phenomena encountered during the testing of the miniature solid propellant motors included erosive propellant burning caused by high flow velocities parallel to the propellant surface, regressive propellant burning as a result of exposed propellant edges, the deposition of aluminum oxide on the nozzle surfaces sufficient to cause aerodynamic nozzle throat geometry changes, and thermal erosion of the nozzle throat at high chamber pressures. A series of tests was conducted to establish the stability of the rocket chamber pressure and the repeatibility of test conditions. Data are presented which define the tests selected to represent the final test matrix. Qualitative observations are also presented concerning the phenomena experienced based on the results of a large number or rocket tests not directly applicable to the final test matrix
- …