152 research outputs found
Modified Boltzmann Transport Equation and Freeze Out
We study Freeze Out process in high energy heavy ion reaction. The
description of the process is based on the Boltzmann Transport Equation (BTE).
We point out the basic limitations of the BTE approach and introduce Modified
BTE. The Freeze Out dynamics is presented in the 4-dimensional space-time in a
layer of finite thickness, and we employ Modified BTE for the realistic Freeze
Out description.Comment: 9 pages, 2 figure
The 3rd Flow Component as a QGP Signal
Earlier fluid dynamical calculations with QGP show a softening of the
directed flow while with hadronic matter this effect is absent. On the other
hand, we indicated that a third flow component shows up in the reaction plane
as an enhanced emission, which is orthogonal to the directed flow. This is not
shadowed by the deflected projectile and target, and shows up at measurable
rapidities, . To study the formation of this effect initial stages
of relativistic heavy ion collisions are studied. An effective string rope
model is presented for heavy ion collisions at RHIC energies. Our model takes
into account baryon recoil for both target and projectile, arising from the
acceleration of partons in an effective field. The typical field strength
(string tension) for RHIC energies is about 5-12 GeV/fm, what allows us to talk
about "string ropes". The results show that QGP forms a tilted disk, such that
the direction of the largest pressure gradient stays in the reaction plane, but
deviates from both the beam and the usual transverse flow directions. The
produced initial state can be used as an initial condition for further
hydrodynamical calculations. Such initial conditions lead to the creation of
third flow component. Recent measurements are promising that this effect
can be used as a diagnostic tool of the QGP
Covariant description of kinetic freeze out through a finite time-like layer
The Freeze Out (FO) problem is addressed for a covariant FO probability and a
finite FO layer with a time-like normal vector continuing the line of studies
introduced in Ref. [1]. The resulting post FO momentum distribution functions
are presented and discussed. We show that in general the post FO distributions
are non-thermal and asymmetric distributions even for time-like FO situations.Comment: 10 pages, 12 figures, major rewrite with changed content, corrected
typos and new references adde
Covariant description of kinetic freeze out through a finite space-like layer
The problem of Freeze Out (FO) in relativistic heavy ion reactions is
addressed. We develop and analyze an idealized one-dimensional model of FO in a
finite layer, based on the covariant FO probability. The resulting post FO
phase-space distributions are discussed for different FO probabilities and
layer thicknesses.Comment: 16 pages, 19 figures, changed content, references adde
Relative risks for Stroke by Age, Sex, and Population Based on Follow-up of 18 European Populations in the MORGAM Project
Particlization in hybrid models
In hybrid models, which combine hydrodynamical and transport approaches to
describe different stages of heavy-ion collisions, conversion of fluid to
individual particles, particlization, is a non-trivial technical problem. We
describe in detail how to find the particlization hypersurface in a 3+1
dimensional model, and how to sample the particle distributions evaluated using
the Cooper-Frye procedure to create an ensemble of particles as an initial
state for the transport stage. We also discuss the role and magnitude of the
negative contributions in the Cooper-Frye procedure.Comment: 18 pages, 28 figures, EPJA: Topical issue on "Relativistic Hydro- and
Thermodynamics"; version accepted for publication, typos and error in Eq.(1)
corrected, the purpose of sampling and change from UrQMD to fluid clarified,
added discussion why attempts to cancel negative contributions of Cooper-Frye
are not applicable her
Longitudinal Scaling of Elliptic Flow in Landau Hydrodynamics
This study presents generalization of the Landau hydrodynamic solution for
multiparticle production applied to non-central relativistic heavy ion
collisions. Obtained results shows longitudinal scaling of elliptic flow
as a function of rapidity shifted by beam rapidity () for different
energies ( GeV and 200 GeV) and for different systems
(Au-Au and Cu-Cu). It is argued, that the elliptic flow and its longitudinal
scaling is due to the initial transverse energy density distribution and
initial longitudinal thickness effect.Comment: 7 pages 1 figur
Trends in suicide in a Lithuanian urban population over the period 1984â2003
BACKGROUND: Throughout the last decade of the twentieth century, Lithuania had the highest suicide rates in Europe among both men and women aged 25â64 years. The rates increased from 1986 until 1995, but later there was a slight decrease. This paper describes the trends in suicide deaths in urban population in Lithuania by gender, dates and suicide method over the period 1984â2003. METHODS: Data from the regional mortality register were used to analyze suicide deaths among all men and women aged 25â64 years in Kaunas city, Lithuania over the period 1984â2003. Age-standardized death rates per 100,000 persons (using European standard population) were calculated by gender, suicide method and dates. A joinpoint regression method was used to estimate annual percentage changes (EPACs) and to detect points where the trends changed significantly. RESULTS: The frequency of death by suicide among males was 48% higher in 1994â2003 than in 1984â1993. The corresponding increase among females was 28%. The most common methods of suicide among men were hanging, strangulation and suffocation (87.4% among all suicide deaths). The proportions of hanging, strangulation and suffocation in males increased by 6.9% â from 83.9% to 89.7% â compared to a 24.2% increase in deaths from handgun, rifle and shotgun firearm discharges and a 216.7% increase in deaths from poisoning with solvents, gases, pesticides and vapors. Among females, the most common methods of suicide were hanging, strangulation and suffocation (68.3% of all suicide deaths). The proportion of hanging deaths among females increased during the time period examined, whereas the proportion of poisonings with solid or liquid substances decreased. CONCLUSION: Suicide rates increased significantly among urban men aged 25â64 years in Lithuania throughout the period 1984â2003, whereas among women an increasing but statistically insignificant trend was observed. There were changes in the suicide methods used by both men and women. Changes in the choice of method may have contributed to the changes in suicide rates
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