Papers by Jan Steinheimer
Journal of Physics G: Nuclear and Particle Physics, 2022
We present results of a phase space coalescence approach within the UrQMD transport and -hybrid m... more We present results of a phase space coalescence approach within the UrQMD transport and -hybrid model for a very wide range of beam energies from SIS to LHC. The coalescence model is able to qualitatively describe the whole range of experimental data with a fixed set of parameters. Some systematic deviations are observed for very low beam energies where the role of feed down from heavier nuclei and multi-fragmentation becomes relevant. The coalescence results are mostly very close to the thermal model fits. However, both the coalescence approach as well as thermal fits are struggling to simultaneously describe the triton multiplicities measured with the STAR and ALICE experiment. The double ratio of $tp/d^2$, in the coalescence approach, is found to be essentially energy and centrality independent for collisions of heavy nuclei at beam energies of $\mathrm{E_{lab}}> 10 A$ GeV. On the other hand the clear scaling of the $d/p^2$ and $t/p^3$ ratios with the systems volume is broken ...
We discuss several new developments in the field of strange and heavy flavor physics in high ener... more We discuss several new developments in the field of strange and heavy flavor physics in high energy heavy ion collisions. As shown by many recent theoretical works, heavy flavored particles give us a unique opportunity to study the properties of systems created in these collisions. Two in particular important aspects, the production of (multi) strange hypernuclei and the properties of heavy flavor mesons, are at the core of several future facilities and will be discussed in detail.
Physics Letters B, 2021
Pengcheng Li, 2 Yongjia Wang, Jan Steinheimer, Qingfeng Li, 4 and Hongfei Zhang 5 School of Nucle... more Pengcheng Li, 2 Yongjia Wang, Jan Steinheimer, Qingfeng Li, 4 and Hongfei Zhang 5 School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000, China School of Science, Huzhou University, Huzhou 313000, China Frankfurt Institute for Advanced Studies, Ruth-Moufang-Str. 1, D-60438 Frankfurt am Main, Germany Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, China Joint Department for Nuclear Physics, Lanzhou University and Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, China (Dated: April 20, 2021)
Kirill Taradiy, 2 Kai Zhou, Jan Steinheimer, Roman V. Poberezhnyuk, 1 Volodymyr Vovchenko, and Ho... more Kirill Taradiy, 2 Kai Zhou, Jan Steinheimer, Roman V. Poberezhnyuk, 1 Volodymyr Vovchenko, and Horst Stoecker 5, 6 Frankfurt Institute for Advanced Studies, Giersch Science Center, D-60438 Frankfurt am Main, Germany Xidian-FIAS International Joint Research Center, Giersch Science Center, D-60438 Frankfurt am Main, Germany Bogolyubov Institute for Theoretical Physics, 03680 Kyiv, Ukraine Nuclear Science Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720, USA Institut für Theoretische Physik, Goethe Universität Frankfurt, D-60438 Frankfurt am Main, Germany GSI Helmholtzzentrum für Schwerionenforschung GmbH, D-64291 Darmstadt, Germany (Dated: June 8, 2021)
Astronomische Nachrichten, 2021
The recent discovery of binary neutron star mergers has opened a new and exciting venue of resear... more The recent discovery of binary neutron star mergers has opened a new and exciting venue of research into hot and dense strongly interacting matter. For the first time this elusive state of matter, described by the theory of quantum chromo dynamics, can be studied in two very different environments. On the macroscopic scale in the collisions of neutron stars and on the microscopic scale in collisions of heavy ions at particle collider facilities. We will discuss the conditions that are created in these mergers and the corresponding high energy nuclear collisions. This includes the properties of QCD matter, i.e. the expected equation of state as well as expected chemical and thermodynamic properties of this exotic matter. To explore this matter in the laboratorya new research prospect is available at the Facility for Antiproton and Ion Research, FAIR. The new facility is being constructed adjacent to the existing accelerator complex of the GSI Helmholtz Center for Heavy Ion Research at Darmstadt/Germany, expanding the research goals and technical possibilities substantially. The worldwide unique accelerator and experimental facilities of FAIR will open the way for a broad spectrum of unprecedented research supplying a variety of experiments in hadron, nuclear, atomic and plasma physics as well as biomedical and material science which will be briefly described.
European Journal of Physics, 2021
Collisions of atomic nuclei at relativistic velocities allow to recreate the conditions encounter... more Collisions of atomic nuclei at relativistic velocities allow to recreate the conditions encountered in neutron stars or in the early universe micro-seconds after the Big Bang. These reactions are performed in today's largest accelerator facilities, e.g. at CERN in Geneva, at the Relativistic Heavy Ion Collider at Brookhaven, NY or in the planned FAIR facility in Darmstadt Germany. During such a collision the matter is heated up to hundreds of MeV (billions of degrees) and compressed to densities of 3 − 10 times the density inside ordinary atomic nuclei (i.e. 10 17 − 10 18 kg/m 3). Usually these collisions are studied via the measurement of a multitude of strongly interacting particles, called hadrons, that are emitted at the end of the collision. However, also some photons are created. These photons are of special interest as they allow to look into the early stage of the collisions, because they are only very weakly (namely only electromagnetically) interacting with the hadrons of the created fireball. This paper elucidates the physics of the photons and what can be learned from them.
Journal of High Energy Physics, 2021
A novel method for identifying the nature of QCD transitions in heavy-ion collision experiments i... more A novel method for identifying the nature of QCD transitions in heavy-ion collision experiments is introduced. PointNet based Deep Learning (DL) models are developed to classify the equation of state (EoS) that drives the hydrodynamic evolution of the system created in Au-Au collisions at 10 AGeV. The DL models were trained and evaluated in different hypothetical experimental situations. A decreased performance is observed when more realistic experimental effects (acceptance cuts and decreased resolutions) are taken into account. It is shown that the performance can be improved by combining multiple events to make predictions. The PointNet based models trained on the reconstructed tracks of charged particles from the CBM detector simulation discriminate a crossover transition from a first order phase transition with an accuracy of up to 99.8%. The models were subjected to several tests to evaluate the dependence of its performance on the centrality of the collisions and physical par...
Physics Letters B, 2020
A new method of event characterization based on Deep Learning is presented. The PointNet models c... more A new method of event characterization based on Deep Learning is presented. The PointNet models can be used for fast, online event-by-event impact parameter determination at the CBM experiment. For this study, UrQMD and the CBM detector simulation are used to generate Au+Au collision events at 10 AGeV which are then used to train and evaluate PointNet based architectures. The models can be trained on features like the hit position of particles in the CBM detector planes, tracks reconstructed from the hits or combinations thereof. The Deep Learning models reconstruct impact parameters from 2-14 fm with a mean error varying from -0.3 to 0.2 fm. For impact parameters in the range of 5-14 fm, a model which uses the combination of hit and track information of particles has a relative precision of 4-9 % and a mean error of -0.05 to 0.15 fm. This new method of event-classification is shown to be more accurate and less model dependent than conventional methods and can utilize the performance boost of modern GPU processor units.
Modern Physics Letters A, 2020
The difference in elliptic flow between protons and antiprotons, produced in [Formula: see text] ... more The difference in elliptic flow between protons and antiprotons, produced in [Formula: see text] collisions at center-of-mass energies [Formula: see text], is studied within a modified version of the ultra-relativistic quantum molecular dynamics (UrQMD) model. Two different model scenarios are compared: the cascade mode and the mean field mode which includes potential interactions for both formed and pre-formed hadrons. The model results for the elliptic flow of protons and the relative elliptic flow difference between protons and antiprotons obtained from the mean field mode agree with the available experimental data, while the elliptic flow difference is near zero for the cascade mode. Our results show that the elliptic flow splitting, observed for particles and antiparticles, can be explained by the inclusion of proper hadronic interactions. In addition, the difference in elliptic flow between protons and antiprotons depends on the centrality and the rapidity window. With smaller...
Nuclear Physics A, 2021
Cumulants scale with volume (extensive): Volume not well controlled in heavy ion collisions Cumul... more Cumulants scale with volume (extensive): Volume not well controlled in heavy ion collisions Cumulant Ratios: Latest STAR result on net-proton cumulants 4 K 4 K 2 "Baseline" K 4 /K 2 follows expectation for CP , K 3 /K 2 no so much….. URQMD totally fails to get trend for K 4 /K 2 ! X. Luo, NPA 956 (2016) 75 K 3 /K 2 Skellam "Baseline" Further insights: Correlations 5 Dip at 19.6 GeV from NEGATIVE C 2 ! Based on prelim. STAR data Based on prelim. STAR data
Proceedings of 8th International Workshop on Critical Point and Onset of Deconfinement — PoS(CPOD 2013), 2013
This work presents an effective model for strongly interacting matter and the QCD equation of sta... more This work presents an effective model for strongly interacting matter and the QCD equation of state (EoS). The model includes both hadron and quark degrees of freedom and takes into account the transition of chiral symmetry restoration as well as the deconfinement phase transition. At low temperatures T and baryonic densities ρ B a hadron resonance gas is described using a SU(3)flavor sigma-omega model and a quark phase is introduced in analogy to PNJL models for higher T and ρ B. In this way, the correct asymptotic degrees of freedom are used in a wide range of T and ρ B. Here, results of this model concerning the chiral and deconfinement phase transitions and thermodynamic model properties are presented. Large hadron resonance multiplicities in the transition region emphasize the importance of heavy-mass resonance states in this region and their impact on the chiral transition behavior. The resulting phase diagram of QCD matter at small chemical potentials is in line with latest lattice QCD and thermal model results.
Journal of Physics G: Nuclear and Particle Physics, 2020
We explore the directed, elliptic, triangular and quadrangular flow of deuterons in Au+Au reactio... more We explore the directed, elliptic, triangular and quadrangular flow of deuterons in Au+Au reactions at a beam energy of 1.23 AGeV within the UrQMD approach. These investigations are of direct relevance for the HADES experiment at GSI that has recently presented first data on the flow of light clusters in Au+Au collisions at 1.23 AGeV. To address the deuteron flow, UrQMD has been extended to include deuteron formation by coalescence. We find that this ansatz provides a very good description of the measured deuteron flow data, if a hard equation of state is used for the simulation. In addition we show that light cluster formation has a sizable impact on the proton flow and has to be taken into account to obtain reliable results in the forward/backward region. Based on the observed scaling of the flow, which is a natural result of coalescence, we conclude that deuteron production at GSI energies is a final state recombination effect. Finally, we also discuss the scaling relations of th...
Journal of Physics: Conference Series, 2016
In these proceedings we discuss recent developments in the microscopic description of strange par... more In these proceedings we discuss recent developments in the microscopic description of strange particle production in nuclear collisions. We put a special emphasis on the production of hypernuclei at the upcoming FAIR and NICA facilities as well as the deep sub threshold, and Ξ- production yields measured with the HADES experiment. Employing new resonance decay channels we obtain a satisfactory description of and Ξ- production in deep sub threshold Ar+KCl reactions. Our results implicate that no new medium effects are required to describe the rare strange particle production data from low energy nuclear collisions.
EPJ Web of Conferences, 2015
We discuss the effects of the final hadronic state, in ultra-relativistic nuclear collisions, on ... more We discuss the effects of the final hadronic state, in ultra-relativistic nuclear collisions, on hadronic resonance properties and measurable production rates. In particular we will compare our results with recent ALICE data on resonance production. We show that the hadronic phase of the system evolution has a considerable impact on the measured resonance ratios and p T spectra. We also discuss some of the remaining uncertainties in the model and how they may be addressed in future studies.
Journal of Physics: Conference Series, 2015
We discuss a novel approach to describe the evolution of a fireball, created in a high-energy nuc... more We discuss a novel approach to describe the evolution of a fireball, created in a high-energy nuclear collision, experiencing spinodal instabilities due to the first-order deconfinement phase transition of quantum chromo dynamics (QCD). We show that initial density fluctuations in these collisions are enhanced in the mechanically unstable region of the QCD phase diagram. In our study we find that the most favorable energy range for observing these density enhancements is at the lower end of the SIS100 accelerator at FAIR, currently under construction. Furthermore we discuss how one can distinguish and constrain different types of QCD phase transitions, one of hadron-quark type and one of liquid-gas type, leading to strong differences in the dynamical evolution of the QCD medium.
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Papers by Jan Steinheimer