244 research outputs found
Exact Three Dimensional Casimir Force Amplitude, -function and Binder's Cumulant Ratio: Spherical Model Results
The three dimensional mean spherical model on a hypercubic lattice with a
film geometry under periodic boundary conditions is
considered in the presence of an external magnetic field . The universal
Casimir amplitude and the Binder's cumulant ratio are calculated
exactly and found to be and
A discussion on the relations
between the finite temperature -function, usually defined for quantum
systems, and the excess free energy (due to the finite-size contributions to
the free energy of the system) scaling function is presented. It is
demonstrated that the -function of the model equals 4/5 at the bulk critical
temperature . It is analytically shown that the excess free energy is a
monotonically increasing function of the temperature and of the magnetic
field in the vicinity of This property is supposed to hold for any
classical -dimensional model with a film geometry under periodic
boundary conditions when . An analytical evidence is also presented to
confirm that the Casimir force in the system is negative both below and in the
vicinity of the bulk critical temperature Comment: 12 pages revtex, one eps figure, submitted to Phys. Rev E A set of
references added with the text needed to incorporate them. Small changes in
the title and in the abstrac
Lifetime measurement of candidate chiral doublet bands in the 103,104Rh isotopes with the recoil-distance Doppler-shift method in inverse kinematics
Casimir forces in binary liquid mixtures
If two ore more bodies are immersed in a critical fluid critical fluctuations
of the order parameter generate long ranged forces between these bodies. Due to
the underlying mechanism these forces are close analogues of the well known
Casimir forces in electromagnetism. For the special case of a binary liquid
mixture near its critical demixing transition confined to a simple parallel
plate geometry it is shown that the corresponding critical Casimir forces can
be of the same order of magnitude as the dispersion (van der Waals) forces
between the plates. In wetting experiments or by direct measurements with an
atomic force microscope the resulting modification of the usual dispersion
forces in the critical regime should therefore be easily detectable. Analytical
estimates for the Casimir amplitudes Delta in d=4-epsilon are compared with
corresponding Monte-Carlo results in d=3 and their quantitative effect on the
thickness of critical wetting layers and on force measurements is discussed.Comment: 34 pages LaTeX with revtex and epsf style, to appear in Phys. Rev.
meson production in Au collisions at GeV
The PHENIX experiment has measured meson production in Au
collisions at GeV using the dimuon and dielectron decay
channels. The meson is measured in the forward (backward) -going
(Au-going) direction, () in the transverse-momentum
() range from 1--7 GeV/, and at midrapidity in the
range below 7 GeV/. The meson invariant yields and
nuclear-modification factors as a function of , rapidity, and centrality
are reported. An enhancement of meson production is observed in the
Au-going direction, while suppression is seen in the -going direction, and
no modification is observed at midrapidity relative to the yield in
collisions scaled by the number of binary collisions. Similar behavior was
previously observed for inclusive charged hadrons and open heavy flavor
indicating similar cold-nuclear-matter effects.Comment: 484 authors, 16 pages, 12 figures, 6 tables. v1 is the version
accepted for publication in Phys. Rev. C. Data tables for the points plotted
in the figures are given in the paper itsel
Cross Section and Transverse Single-Spin Asymmetry of Mesons in Collisions at GeV at Forward Rapidity
We present a measurement of the cross section and transverse single-spin
asymmetry () for mesons at large pseudorapidity from
~GeV collisions. The measured cross section for
~GeV/ and is well described by a
next-to-leading-order perturbative-quantum-chromodynamics calculation. The
asymmetries have been measured as a function of Feynman- () from
, as well as transverse momentum () from
~GeV/. The asymmetry averaged over positive is
. The results are consistent with prior
transverse single-spin measurements of forward and mesons at
various energies in overlapping ranges. Comparison of different particle
species can help to determine the origin of the large observed asymmetries in
collisions.Comment: 484 authors, 13 pages, 11 figures, 4 tables, 2008 data. v2 is version
accepted by Phys. Rev. D. Plain text data tables for the points plotted in
figures for this and previous PHENIX publications are (or will be)publicly
available at http://www.phenix.bnl.gov/papers.htm
Systematic study of charged-pion and kaon femtoscopy in AuAu collisions at =200 GeV
We present a systematic study of charged pion and kaon interferometry in
AuAu collisions at =200 GeV. The kaon mean source radii
are found to be larger than pion radii in the outward and longitudinal
directions for the same transverse mass; this difference increases for more
central collisions. The azimuthal-angle dependence of the radii was measured
with respect to the second-order event plane and similar oscillations of the
source radii were found for pions and kaons. Hydrodynamic models qualitatively
describe the similar oscillations of the mean source radii for pions and kaons,
but they do not fully describe the transverse-mass dependence of the
oscillations.Comment: 499 authors, 27 pages, 13 figures, and 11 tables. v2 is the version
accepted for publication in Phys. Rev. C. Plain text data tables for the
points plotted in figures for this and previous PHENIX publications are (or
will be) publicly available at http://www.phenix.bnl.gov/papers.htm
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