345 research outputs found
Higher order anisotropies in the Buda-Lund model: Disentangling flow and density field anisotropies
The Buda-Lund hydro model describes an expanding ellipsoidal fireball, and
fits the observed elliptic flow and oscillating HBT radii successfully. Due to
fluctuations in energy depositions, the fireball shape however fluctuates on an
event-by-event basis. The transverse plane asymmetry can be translated into a
series of multipole anisotropy coefficients. These anisotropies then result in
measurable momentum-space anisotropies, to be measured with respect to their
respective symmetry planes. In this paper we detail an extension of the
Buda-Lund model to multipole anisotropies and investigate the resulting flow
coefficients and oscillations of HBT radii.Comment: 1 column format, 20 pages, 10 figure
Simulation and Validation with Radio-Controlled (RC) Autonomous Vehicles in Roundabout Situation
In the present research paper, the authors provide an extensive overview about a so far uninvestigated approach regarding the research and development (R&D) of Autonomous Vehicle Technologies, an exhaustive investigation concerning the simulation and validation of roundabout situation with radio-controlled (RC) autonomous vehicles, as well as the examination of RC vehicles' applicability in the testing processes of Connected Autonomous Vehicle (CAV) technologies. Through this research project, the authors are offering a thorough analysis concerning the most current Autonomous Driving Systems from the point of view of their operation in roundabout related environments, as well as have developed two small-scaled RC autonomous vehicle models, which are capable of being used in the testing and validation processes concerning research studies related to the field of autonomous vehicles. This paper represents the first of a two-part in-depth examination of the aforementioned subject matter, organized in six sections, each contributing significantly to the realization of the final structure of a unique and comprehensive project
HBT radii from the multipole Buda-Lund model
The Buda-Lund model describes an expanding hydrodynamical system with
ellipsoidal symmetry and fits the observed elliptic flow and oscillating HBT
radii successfully. The ellipsoidal symmetry can be characterized by the second
order harmonics of the transverse momentum distribution, and it can be also
observed in the azimuthal oscillation of the HBT radii measured versus the
second order reaction plane. The model may have to be changed to describe the
experimentally indicated higher order asymmetries. In this paper we detail an
extension of the Buda-Lund hydro model to investigate higher order flow
harmonics and the triangular dependence of the azimuthally sensitive HBT radii.Comment: 4 pages, 6 figures. Presented at the 11th Workshop on Particle
Correlations and Femtoscopy (WPCF 2015), 03-07 Nov 2015, Warsaw, Polan
Two- and three-pion LĂ©vy femtoscopy with PHENIX
The last decades of high energy physics revealed, that in ultra-relativistic
ion-ion collisions, a strongly interacting quark gluon plasma (sQGP) is
created. Varying the collision energy allows for the investigation of the phase
diagram of QCD matter. The nature of the quark-hadron transition can be studied
via femtoscopy, as the investigation of momentum correlations in heavy ion
reactions reveals the space-time structure of the hadron production of the
sQGP. Going beyond the Gaussian assumption the shape of this source may be
described by L\'evy distributions. In this paper we report on recent
femtoscopic measurements of PHENIX, utilizing L\'evy sources.Comment: 8 pages, 6 figures. Presented at the 34th Winter Workshop on Nuclear
Dynamic
LĂ©vy Femtoscopy with PHENIX at RHIC
In this paper we present the measurement of charged pion two-particle femtoscopic correlation functions in s N N = 200 GeV Au + Au collisions in 31 average transverse mass bins, separately for positive and negative pion pairs. Lévy-shaped source distributions yield a statistically acceptable description of the measured correlation functions, with three physical parameters: correlation strength parameter λ , Lévy index α and Lévy scale parameter R. The transverse mass dependence of these Lévy parameters is then investigated. Their physical interpretation is also discussed, and the appearance of a new scaling variable is observed
Exploring the QCD phase diagram via the collision energy dependence of multi-particle femtoscopy with PHENIX
Exploration of the rich structure of the QCD phase diagram is an important topic in the RHIC heavy ion program. One of the ultimate goals of this program is to search for the critical endpoint. Investigation of the space-time structure of hadron emissions at various phase transition points using Bose-Einstein correlations of identical bosons may provide insight on the location of the critical endpoint. PHENIX has performed comprehensive measurements of the Bose-Einstein correlation in Au+Au collisions at root s(NN) = 15, 19, 27, 39, 62.4, and 200 GeV, where we incorporated Levy-type source functions to describe the measured correlation functions. We put particular focus on one of the parameters of the Levy-type source functions, the index of stability alpha, which is related to one of the critical exponents (the so-called correlation exponent eta). We have measured its collision energy and centrality dependence. We have also extended our analysis from two-particle to three-particle correlations to characterize the nature of the hadron emission source. The three particle correlations confirmed the findings of the two-particle correlations, and also provide insight on the pion production mechanism beyond the core-halo model
LĂ©vy femtoscopy with PHENIX at RHIC
Charged pion two-particle correlation functions were measured in 0-30%
centrality 200 GeV Au+Au collisions with the PHENIX experiment at RHIC. The
measured correlation functions can be statistically well described based on the
assumption of Levy-shaped source distributions. In this proceedings paper we
present the Levy parameters of the measured correlation functions: correlation
strength parameter lambda, Levy index alpha and Levy scale parameter R as a
function of pair transverse mass mT, in 31 bins from 228 to 871 MeV, separately
for positive and negative pion pairs. We discuss the physical interpretation of
the mT dependence of the parameters.Comment: Write-up of a poster presented at the XXXVII International Symposium
on Physics in Collisio
Event-by-event investigation of the two-particle source function in heavy-ion collisions with EPOS
Exploring the shape of the pair-source function for particles such as pions
or kaons has been an important goal of heavy-ion physics, and substantial
effort has been made in order to understand the underlying physics behind the
experimental observations of non-Gaussian behavior. In experiments, since no
direct measurement of the source function is possible, quantum-statistical
momentum correlations are utilized to gain information about the space-time
geometry of the particle emitting source. Event generators, such as EPOS,
however, provide direct access to the freeze-out coordinates of final state
particles, and thus the source function can be constructed and investigated.
The EPOS model is a sophisticated hybrid model where the initial stage
evolution of the system is governed by Parton-Based Gribov-Regge theory, and
subsequently a hydrodynamic evolution is utilized, followed by hadronization
and hadron dynamics. EPOS has already proven to be successful in describing
several different experimental observations for systems characterized by baryon
chemical potential close to zero, but so far the source shape has not been
explored in detail. In this paper we discuss an event-by-event analysis of the
two-particle source function in = 200 GeV Au+Au collisions
generated by the EPOS model. We find that when utilizing all stages of the
model, L\'evy-shaped distributions (unlike Gaussian distributions) provide a
good description of the source shape in the individual events. Hence it is
clear that it is not the event averaging that creates the non-Gaussian features
in the pair distributions. Based on this observation, we determine
L\'evy-parameters of the source as a function of event centrality and particle
momentum.Comment: 13 pages, 6 figure
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