14,336 research outputs found
Search for the onset of baryon anomaly at RHIC-PHENIX
The baryon production mechanism at the intermediate (2 - 5 GeV/) at
RHIC is still not well understood. The beam energy scan data in Cu+Cu and Au+Au
systems at RHIC may provide us a further insight on the origin of the baryon
anomaly and its evolution as a function of . In 2005 RHIC
physics program, the PHENIX experiment accumulated the first intensive low beam
energy data in Cu+Cu collisions. We present the preliminary results of
identified charged hadron spectra in Cu+Cu at = 22.5 and 62.4
GeV using the PHENIX detector. The centrality and beam energy dependences of
(anti)proton to pion ratios and the nuclear modification factors for charged
pions and (anti)protons are presented.Comment: 5 pages, 9 figures, proceedings for Hot Quarks 2006 workshop,
Villasimius, Sardinia, Italy, May 15 - 20, 2006. Proceedings of the
conference will be published in The European Physical Journal
An Energy-Minimization Finite-Element Approach for the Frank-Oseen Model of Nematic Liquid Crystals: Continuum and Discrete Analysis
This paper outlines an energy-minimization finite-element approach to the
computational modeling of equilibrium configurations for nematic liquid
crystals under free elastic effects. The method targets minimization of the
system free energy based on the Frank-Oseen free-energy model. Solutions to the
intermediate discretized free elastic linearizations are shown to exist
generally and are unique under certain assumptions. This requires proving
continuity, coercivity, and weak coercivity for the accompanying appropriate
bilinear forms within a mixed finite-element framework. Error analysis
demonstrates that the method constitutes a convergent scheme. Numerical
experiments are performed for problems with a range of physical parameters as
well as simple and patterned boundary conditions. The resulting algorithm
accurately handles heterogeneous constant coefficients and effectively resolves
configurations resulting from complicated boundary conditions relevant in
ongoing research.Comment: 31 pages, 3 figures, 3 table
A preliminary phylogeographic study of Flavopunctelia and Punctelia inferred from rDNA ITS-sequences
A preliminary phylogeny of the genera Flavopunctelia and Punctelia is presented. Genus and species delimitations have been investigated using ITS rDNA-sequencing of populations from different continents. Current genus delimitations of Flavopunctelia, Punctelia and Parmelia are confirmed and the species status of recently resurrected Punctelia ulophylla is confirmed. The status of three cryptic species, Flavopunctelia soredica, Punctelia perreticulata and P. stictica is discussed. Flavopunctelia borrerioides and Punctelia perreticulata are reported from China for the first time.Esitatakse perekondade Flavopunctelia ja Punctelia esialgne fülogeneesi rekonstruktsioon. Perekondade ja liikide eraldamist on uuritud erinevatelt kontinentidelt pärinevate populatsioonide ITS rDNA sekventside alusel. Senine perekondade Flavopunctelia, Punctelia ja Parmelia piiritlemine on leidnud kinnitust, samuti liigi Punctelia ulophylla staatus. Arutletakse kolme krüptilise liigi, Flavopunctelia soredica, Punctelia perreticulata ja P. stictica staatuse üle. Teatatakse liikide Flavopunctelia borrerioides ja Punctelia perreticulata esmasleidudest HiinasFil: Thell, Arne. Lund University; SueciaFil: Herber, B.. Universitat Hamburg; AlemaniaFil: Aptroot, A.. Centraalbureau voor Schimmelcultures; Países BajosFil: Adler, Monica Teresa. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Micología y Botánica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Micología y Botánica; ArgentinaFil: Feuerer, T.. Universitat Hamburg; AlemaniaFil: Kärnefelt, Ingvar. Lund University; Sueci
Pseudorapidity dependence of parton energy loss in relativistic heavy ion collisions
We analyze the recent data from the BRAHMS Collaboration on the
pseudorapidity dependence of nuclear modification factors in Au+Au collisions
at = 200 GeV by using the full three dimensional hydrodynamic
simulations for the density effects on parton energy loss. We first compute the
transverse spectra at and 2.2, and next take a ratio
, where is a nuclear
modification factor. It is shown that hydrodynamic components account for
at low and that quenched pQCD components lead
at high which are consistent with the data.
Strong suppression at is compatible with the parton energy loss in
the final state.Comment: 5 pages, 4 figures; one figure adde
Buda-Lund hydro model for ellipsoidally symmetric fireballs and the elliptic flow at RHIC
The ellipsoidally symmetric extension of Buda-Lund hydrodynamic model is
shown here to yield a natural description of the pseudorapidity dependence of
the elliptic flow , as determined recently by the PHOBOS experiment
for Au+Au collisions at and 200 GeV. With the same set of
parameters, the Buda-Lund model describes also the transverse momentum
dependence of of identified particles at mid-rapidity. The results
confirm the indication for quark deconfinement in Au+Au collisions at RHIC,
obtained from a successful Buda-Lund hydro model fit to the single particle
spectra and two-particle correlation data, as measured by the BRAHMS, PHOBOS,
PHENIX and STAR collaborations.Comment: 16 pages, 2 figures, 1 table added, discussion extended and an
important misprint in the caption of Fig. 1 is correcte
Expansion for -Core Percolation
The physics of -core percolation pertains to those systems whose
constituents require a minimum number of connections to each other in order
to participate in any clustering phenomenon. Examples of such a phenomenon
range from orientational ordering in solid ortho-para mixtures to
the onset of rigidity in bar-joint networks to dynamical arrest in
glass-forming liquids. Unlike ordinary () and biconnected ()
percolation, the mean field -core percolation transition is both
continuous and discontinuous, i.e. there is a jump in the order parameter
accompanied with a diverging length scale. To determine whether or not this
hybrid transition survives in finite dimensions, we present a expansion
for -core percolation on the -dimensional hypercubic lattice. We show
that to order the singularity in the order parameter and in the
susceptibility occur at the same value of the occupation probability. This
result suggests that the unusual hybrid nature of the mean field -core
transition survives in high dimensions.Comment: 47 pages, 26 figures, revtex
Diagnosing Energy Loss: PHENIX Results on High-pT Hadron Spectra
Measurements of inclusive spectra of hadrons at large transverse momentum
over a broad range of energy in different collision systems have been performed
with the PHENIX experiment at RHIC. The data allow to study the energy and
system size dependence of the suppression observed in RAA of high-pT hadrons at
sqrt(s_NN)= 200 GeV. Due to the large energy range from sqrt(s_NN)= 22 GeV to
200 GeV, the results can be compared to results from CERN SPS at a similar
energy. The large Au+Au dataset from the 2004 run of RHIC also allows to
constrain theoretical models that describe the hot and dense matter produced in
such collisions. Investigation of particle ratios such as eta/pi0 helps
understanding the mechanisms of energy loss.Comment: 4 pages, 6 figures. To appear in the proceedings of the 19th
International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions
(Quark Matter 2006), Shanghai, China, November 14-20, 200
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