679 research outputs found
Production of spectator hypermatter in relativistic heavy-ion collisions
We study the formation of large hyper-fragments in relativistic heavy-ion
collisions within two transport models, DCM and UrQMD. Our goal is to explore a
new mechanism for the formation of strange nuclear systems via capture of
hyperons by relatively cold spectator matter produced in semi-peripheral
collisions. We investigate basic characteristics of the produced
hyper-spectators and evaluate the production probabilities of multi-strange
systems. Advantages of the proposed mechanisms over an alternative coalescence
mechanism are analysed. We also discuss how such systems can be detected taking
into account the background of free hyperons. This investigation is important
for the development of new experimental methods for producing hyper-nuclei in
peripheral relativistic nucleus-nucleus collisions, which are now underway at
GSI and are planned for the future FAIR and NICA facilities.Comment: 28 pages, including 10 figures. Submitted to Phys. Rev.
Elliptic Flow Analysis at RHIC with the Lee-Yang Zeroes Method in a Relativistic Transport Approach
The Lee-Yang zeroes method is applied to study elliptic flow () in Au+Au
collisions at ~GeV, with the UrQMD model. In this transport
approach, the true event plane is known and both the nonflow effects and
event-by-event fluctuations exist. Although the low resolutions prohibit
the application of the method for most central and peripheral collisions, the
integral and differential elliptic flow from the Lee-Yang zeroes method agrees
with the exact values very well for semi-central collisions.Comment: 4 pages, 4 figure
Enhanced Event-by-Event Fluctuations in Pion Multiplicity as a Signal of Disoriented Chiral Condensates at RHIC
The factorial moments of the pion multiplicity distributions are calculated
with HIJING and UrQMD and found to be independent of the pT range included, in
contrast to recent simulations with the linear sigma model which leads to large
enhancements for pions with transverse kinetic energies below 200 MeV. This
supports the use of the ratio of the factorial moments of low and high pT pions
as a signal of ``new'' physics at low momentum scales, such as the formation of
disoriented chiral condensates.Comment: 4 pages total, incl 4 eps figures ([email protected]
Nucleosynthesis of light nuclei and hypernuclei in central Au+Au collisions at =3 GeV
We analyze the experimental data on nuclei and hypernuclei yields recently
obtained by the STAR collaboration. The hybrid dynamical and statistical
approaches which have been developed previously are able to describe the
experimental data reasonably. We discuss the intriguing difference between the
yields of normal nuclei and hypernuclei which may be related to the properties
of hypermatter at subnuclear densities. Most importantly new (hyper-)nuclei
could be detected via particle correlations, and such measurements are relevant
to pin down the production mechanism.Comment: 7 pages, 6 figure
Establishment of a model of murine odontoblasts underexpressing Pkd1 using shRNA
We have previously shown that PKD1, the gene encoding Polycystin-1 (or TRPP1) is expressed in human odontoblasts and that this protein is localized at the primary cilium of the cell. Nevertheless, its function remain unclear in this cell even if studies on osteoblasts, osteocytes and chondrocytes give TRPP1 as a promising candidate for mechanotransduction in response to mechanical stress. Consequently, to evaluate the role of TRPP1 in this transduction process, we needed first to generate an in vitro murine model down expressing Pkd1. Using lentivirus-mediated shRNA technology, we obtained a 60% suppression of Pkd1 mRNA expression in transfected MO6-G3 cells associated with a decrease of cell proliferation. Thus, establishment of this murine odontoblast model underexpressing Pkd1 associated with applied mechanical forces (compression or shear stress) will allow us to go further in the determination of TRPP1 involvement in odontoblasts mechanotransduction. Nous avons montré précédemment que PKD1, le gène codant pour la polycystine 1 ou TRPP1, est exprimé dans les cultures d’odontoblastes humains avec une localisation préférentielle de la protéine au niveau des cils primaires. Cependant, la fonction de TRPP1 reste à ce jour inconnue malgré un rôle potentiel de mécanotransducteur mis en évidence dans les ostéoblastes, ostéocytes et chondrocytes. Pour évaluer le rôle de cette protéine dans les odontoblastes nous avons choisi de mettre au point un modèle cellulaire sous-exprimant Pkd1. Ainsi, à l’aide de shRNA, nous avons obtenu une lignée cellulaire de souris (MO6-G3) sous-exprimant de façon stable Pkd1 (60% de sous-expression), et présentant une diminution de la prolifération cellulaire. Ce nouveau modèle cellulaire associé à l’application de forces mécaniques (compression ou étirement) devrait nous permettre d’évaluer l’implication de TRPP1 dans les processus de mécanotransduction des odontoblastes
Equation of state at FAIR energies and the role of resonances
Two microscopic models, UrQMD and QGSM, are used to extract the effective
equation of state (EOS) of locally equilibrated nuclear matter produced in
heavy-ion collisions at energies from 11.6 AGeV to 160 AGeV. Analysis is
performed for the fixed central cubic cell of volume V = 125 fm**3 and for the
expanding cell that followed the growth of the central area with uniformly
distributed energy. For all reactions the state of local equilibrium is nearly
approached in both models after a certain relaxation period. The EOS has a
simple linear dependence P/e = c_s**2 with 0.12 < c_s**2 < 0.145. Heavy
resonances are shown to be responsible for deviations of the c_s**2(T) and
c_s**2(mu_B) from linear behavior. In the T-mu_B and T-mu_S planes the EOS has
also almost linear dependence and demonstrates kinks related not to the
deconfinement phase transition but to inelastic freeze-out in the system.Comment: SQM2008 proceedings, 6 page
Hadron yields in Au+Au/Pb+Pb at RHIC and LHC from thermalized minijets
We calculate the yields of a variety of hadrons for RHIC and LHC energies
assuming thermodynamical equilibration of the produced minijets, and using as
input results from pQCD for the energy densities at midrapidity. In the
calculation of the production of partons and of transverse energy one has to
account for nuclear shadowing. By using two parametrizations for the gluon
shadowing one derives energy densities differing strongly in magnitude. In this
publication we link those perturbatively calculated energy densities of partons
via entropy conservation in an ideal fluid to the hadron multiplicities at
chemical freeze-out.Comment: 11 pages, 2 .eps figure
- …