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 Lévy 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

Lévy 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

Lévy 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 $\sqrt{s_{NN}}$ = 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