## About

246

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Introduction

Additional affiliations

August 2017 - present

August 2013 - July 2017

January 2011 - July 2013

Education

June 2008 - June 2011

## Publications

Publications (246)

We introduce a Python package that provides simple and unified access to a collection of datasets from fundamental physics research—including particle physics, astroparticle physics, and hadron- and nuclear physics—for supervised machine learning studies. The datasets contain hadronic top quarks, cosmic-ray-induced air showers, phase transitions in...

It is demonstrated that the presence of a phase transition in heavy ion collisions, at beam energies that probe dense QCD matter, leads to a significant enhancement of the dilepton yield per produced pion due to the extended emission time. In addition, the temperature of low mass dileptons shows a modest decrease due to the mixed phase. The emissio...

The pion-to-proton ratio is identified as a potential signal for a non-equilibrium first-order chiral phase transition in heavy-ion collisions, as the pion multiplicity is directly related to entropy production. To showcase this effect, a non-equilibrium Bjorken expansion starting from realistic initial conditions along a Taub adiabat is used to si...

Hanbury-Brown-Twiss (HBT) correlations for charged pions in central Au+Au collisions at $\sqrt{s_\mathrm{NN}}=2.4 - 7.7~\text{GeV}$ (corresponding to beam kinetic energies in the fixed target frame from $E_{\rm{lab}}=1.23~\text{to}~30~\text{GeV/nucleon}$) are calculated using the UrQMD model with different equations of state. The effects of a phase...

A set of different equations of state is implemented in the molecular dynamics part of a non-equilibrium transport simulation (UrQMD) of heavy-ion collisions. It is shown how different flow observables are affected by the density dependence of the equation of state. In particular, the effects of a phase transition at high density are explored, incl...

We study the production of clusters and hypernuclei at midrapidity employing the Parton-Hadron-Quantum-Molecular-Dynamics (PHQMD) approach, a microscopic n-body transport model based on the QMD propagation of the baryonic degrees of freedom with density dependent 2-body potential interactions. In PHQMD the cluster formation occurs dynamically, caus...

The recent measurement of Ag+Ag reactions at $E_\mathrm{lab}=1.23A$ GeV by the HADES experiment, together with the previous Au+Au data at the same beam energy energy, allows to explore the differences between a small and large collision system at high baryon densities. From this, one expects to learn further details on the equation of state of nucl...

The hadron-quark phase transition in quantum chromodyanmics has been suggested as an alternative explosion mechanism for core-collapse supernovae. We study the impact of three different hadron-quark equations of state (EoS) with first-order (DD2F_SF, STOS-B145) and second-order (CMF) phase transitions on supernova dynamics by performing 97 simulati...

The effect of isospin-dependent nuclear forces on the inner crust of neutron stars is modeled within the framework of Quantum Molecular Dynamics (QMD). To successfully control the density dependence of the symmetry energy of neutron-star matter below nuclear saturation density, a mixed vector-isovector potential is introduced. This approach is insp...

We propose to extend the commonly known flow analysis in the transverse $p_x$-$p_y$ plane to novel flow coefficients based on the angular distribution in the $p_x$-$p_z$ and $p_y$-$p_z$ planes. The new flow coefficients, called $u_n$ and $w_n$ (in addition to $v_n$), turn out to be also highly sensitive to the nuclear Equation-of-State and can be u...

We investigate the coalescence factors $B_2$ and $B_3$ at low collision energies ($\sqrt{s_\mathrm{NN}}<6$ GeV) with special focus on the HADES and RHIC-BES experiments. It is shown that, in order to properly interpret the coalescence factors $B_A$, two important corrections are necessary: I) $B_2$ has to be calculated using the proton $\times$ neu...

Correlations between the harmonic flow coefficients $$v_1$$ v 1 , $$v_2$$ v 2 , $$v_3$$ v 3 and $$v_4$$ v 4 of nucleons in semi-peripheral Au+Au collisions at a beam energy of 1.23 AGeV are investigated within the hadronic transport approach ultra-relativistic quantum molecular dynamics (UrQMD). In contrast to ultra-relativistic collision energies...

It is shown that the initial compression in central heavy ion collisions at beam energies of $$E_{\mathrm {lab}}=1-10A$$ E lab = 1 - 10 A GeV depends dominantly on the underlying equation of state and only marginally on the model used for the dynamical description. To do so, a procedure to incorporate any equation of state in the UrQMD transport mo...

The hadron-quark phase transition in quantum chromodyanmics has been suggested as an alternative explosion mechanism for core-collapse supernovae. We study the impact of three different hadron-quark equations of state (EoS) with first-order (DD2F, STOF-B145) and second-order (CMF) phase transitions on supernova dynamics by performing 97 simulations...

Correlations between the harmonic flow coefficients $v_1$, $v_2$, $v_3$ and $v_4$ of nucleons in semi-peripheral Au+Au collisions at a beam energy of 1.23~AGeV are investigated within the hadronic transport approach Ultra-relativistic Quantum Molecular Dynamics (UrQMD). In contrast to ultra-relativistic collision energies (where the flow coefficien...

We compare the microscopic transport models UrQMD, PHSD, PHQMD, and SMASH to make predictions for the upcoming Ag+Ag data at E lab = 1.58 AGeV (√s NN = 2.55 GeV) by the HADES collaboration. We study multiplicities, spectra and eﬀective source temperatures of protons, π ±,0 , K ± , the η, Λ+Σ ⁰ and the Ξ ⁻ within these models. Despite variations in...

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...

The tracking of pathogen burden and host responses with minimal-invasive methods during respiratory infections is central for monitoring disease development and guiding treatment decisions. Utilizing a standardized murine model of respiratory Influenza A virus (IAV) infection, we developed and tested different supervised machine learning models to...

We point out that the variance of net-baryon distribution normalized by the Skellam distribution baseline, κ2[B−B¯]/〈B+B¯〉, is sensitive to the possible modification of (anti)baryon yields due to BB¯ annihilation in the hadronic phase. The corresponding measurements can thus place stringent limits on the magnitude of the BB¯ annihilation and its in...

As a way to find analogies and differences in the dynamics of hot and dense matter under extreme conditions, we present the first self-consistent relativistic-hydrodynamic calculations of both neutron-star mergers and low-energy heavy-ion collisions employing the same equation of state. By a direct comparison of the evolution of quantities such as...

The formation of deuterons in heavy-ion collisions at relativistic energies is investigated by employing two recently advanced models -- the Minimum Spanning Tree (MST) method and the coalescence model by embedding them in the PHQMD and the UrQMD transport approaches. While the coalescence mechanism combines nucleons into deuterons at the kinetic f...

It is shown that the initial compression in central heavy ion collisions at beam energies of $E_\mathrm{lab}=1-10A$~GeV depends dominantly on the underlying equation of state and only marginally on the model used for the dynamical description. To do so, a procedure to incorporate any equation of state in the UrQMD transport model is introduced. In...

We compare the microscopic transport models UrQMD, PHSD, PHQMD, and SMASH to make predictions for the upcoming Ag+Ag data at $E_\mathrm{lab}=1.58$~$A$GeV ($\sqrt{s_\mathrm{NN}}=2.55$~GeV) by the HADES collaboration. We study multiplicities, spectra and effective source temperatures of protons, $\pi^{\pm,0}$, $K^\pm$, the $\eta$, $\Lambda+\Sigma^0$...

Using the EPOS3 model with the Ultrarelativistic Quantum Molecular Dynamics (UrQMD) model to describe the hadronic phase, we study the production of short-lived hadronic resonances and the modification of their yields and pT spectra in p−Pb collisions at sNN= 5.02 TeV. High-multiplicity p−Pb collisions exhibit similar behavior to midperipheral Pb-P...

A bstract
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...

The effect of isospin-dependent nuclear forces on the inner crust of neutron stars is modeled within the framework of Quantum Molecular Dynamics (QMD). To successfully control the density dependence of the symmetry energy of neutron-star matter below nuclear saturation density, a coupling potential between the $\omega$ and $\rho$ meson fields is in...

The thermal fit to preliminary HADES data of Au+Au collisions at sNN=2.4 GeV shows two degenerate solutions at T≈50 MeV and T≈70 MeV. The analysis of the same particle yields in a transport simulation of the UrQMD model yields the same features, i.e. two distinct temperatures for the chemical freeze-out. While both solutions yield the same number o...

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...

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 FA...

Earthquakes with magnitude M greater than or equal to 6.5 are potentially destructive events which may cause tremendous devastation, huge economic loss and large numbers of casualties. Models with predictive or forecasting power are still lacking. Nevertheless, the spatial and temporal information of these seismic events can provide important infor...

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 differe...

We introduce a collection of datasets from fundamental physics research -- including particle physics, astroparticle physics, and hadron- and nuclear physics -- for supervised machine learning studies. These datasets, containing hadronic top quarks, cosmic-ray induced air showers, phase transitions in hadronic matter, and generator-level histories,...

We point out that the variance of net-baryon distribution normalized by the Skellam distribution baseline, $\kappa_2[B-\bar{B}]/\langle B+\bar{B}\rangle$, is sensitive to the possible modification of (anti)baryon yields due to $B\bar{B}$ annihilation in the hadronic phase. The corresponding measurements can thus place stringent limits on the magnit...

We study the applicability of a Deep Neural Network (DNN) approach to simulate one-dimensional non-relativistic fluid dynamics. Numerical fluid dynamical calculations are used to generate training data-sets corresponding to a broad range of profiles to perform supervised learning with DNN. The performance of the DNN approach is analyzed, with a foc...

We present different methods of unsupervised learning which can be used for outlier detection in high energy nuclear collisions. This method is of particular interest for heavy ion collisions where a direct comparison of experimental data to model simulations is often ambiguous and it is not easy to determine whether an observation is due to new ph...

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 ne...

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 neut...

Second-order susceptibilities χij11 of baryon, electric, and strangeness, B, Q, and S, charges are calculated in the chiral mean field (CMF) model and compared with available lattice QCD data. The susceptibilities are sensitive to the short-range repulsive interactions between different hadron species, especially to the hardcore repulsion of hypero...

It is shown that the inclusion of hadronic interactions, and in particular nuclear potentials, in simulations of heavy ion collisions at the SPS energy range can lead to obvious correlations of protons. These correlations contribute significantly to an intermittency analysis as performed at the NA61 experiment. The beam energy and system size depen...

It is shown that the inclusion of hadronic interactions, and in particular nuclear potentials, in simulations of heavy ion collisions at the SPS energy range can lead to obvious correlations of protons. These correlations contribute significantly to an intermittency analysis as performed at the NA61 experiment. The beam energy and system size depen...

The thermal fit to preliminary HADES data of Au+Au collisions at $\sqrt{s_{_{NN}}}=2.4$ GeV shows two degenerate solutions at $T\approx50$ MeV and $T\approx70$ MeV. The analysis of the same particle yields in a transport simulation of the UrQMD model yields the same features, i.e. two distinct temperatures for the chemical freeze-out. While both so...

Using the EPOS3 model with UrQMD to describe the hadronic phase, we study the production of short-lived hadronic resonances and the modification of their yields and $p_{T}$ spectra in p-Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV. High-multiplicity p-Pb collisions exhibit similar behavior to mid-peripheral Pb-Pb collisions at LHC energies, and we f...

In this talk we presented a novel technique, based on Deep Learning, to determine the impact parameter of nuclear collisions at the CBM experiment. PointNet based Deep Learning models are trained on UrQMD followed by CBMRoot simulations of Au+Au collisions at 10 AGeV to reconstruct the impact parameter of collisions from raw experimental data such...

The thermodynamic properties of high temperature and high density QCD-matter are studied using the Chiral SU(3)-flavor parity-doublet Polyakov-loop quark-hadron mean-field model, CMF. The CMF model provides a proper description of lattice QCD data, heavy-ions physics, and static neutron stars. The behavior of lines of constant pressure with increas...

The preliminary STAR data for proton cumulants for central collisions at s=7.7GeV component proton multiplicity distribution. We show that this two-component distribution is statistics friendly in that factorial cumulants of surprisingly high orders may be extracted with a relatively small number of events. As a consequence the two-component model...

In this proceeding, we review our recent work using deep convolutional neural network (CNN) to identify the nature of the QCD transition in a hybrid modeling of heavy-ion collisions. Within this hybrid model, a viscous hydrodynamic model is coupled with a hadronic cascade “after-burner”. As a binary classification setup, we employ two different typ...

Possible observables of baryon number clustering due to the instabilities occurring at a first order QCD phase transition are discussed. The dynamical formation of baryon clusters at a QCD phase transition can be described by numerical fluid dynamics, augmented with a gradient term and an equation of state with a mechanically unstable region. It is...

The properties of compact stars and in particular the existence of twin star solutions are investigated within an effective model that is constrained by lattice QCD thermodynamics. The model is modified at large baryon densities to incorporate a large variety of scenarios of first order phase transitions to a phase of deconfined quarks. This is ach...

Hadronic interactions are crucial for the dynamical description of heavy-ion reactions at low collision energies and in the late dilute stages at high collision energies. In particular, the properties and decay channels of resonances are an essential ingredient of hadronic transport approaches. The HADES collaboration measured particle production i...

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 Point...

The search for a first-order phase transition in strongly interacting matter is one of the major objectives in the exploration of the phase diagram of Quantum Chromodynamics (QCD). In the present work we investigate dilepton radiation from the hot and dense fireballs created in Au-Au collisions at projectile energies of 1-2 $A$GeV for potential sig...

We study the influence of the centrality definitionCentrality definition and detector efficiency on the net-proton kurtosis for minimum bias AuAu collisions at a beam energy of GeV by using the UrQMD model. We find that different ways of defining the centrality lead to different cumulant ratiosCumulant ratios. Moreover, we demonstrate that the kurt...

We explore the scaling properties of the elliptic and quadrangular flow of deuterons and protons in Au+Au reactions at a beam energy of 1.23 AGeV within the UrQMD approach. These investigations are of great interest for the HADES experiment at GSI that has recently studied the flow of light nuclei. In the present studies, deuterons are formed via p...

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 whic...

The second order susceptibilities of $B$, $Q$, and $S$ charges, $\chi^{11}_{ij}$, are calculated in the CMF model and compared to the available lattice QCD data. It is found that the susceptibilities are very sensitive to the short range repulsive interactions between different hadron species, especially to the not so well constrained hardcore repu...

In this proceeding, we review our recent work using deep convolutional neural network (CNN) to identify the nature of the QCD transition in a hybrid modeling of heavy-ion collisions. Within this hybrid model, a viscous hydrodynamic model is coupled with a hadronic cascade "after-burner". As a binary classification setup, we employ two different typ...

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 $A$GeV which are then used to train and evaluate Poi...

We investigate simultaneous effects of finite system size and global charge conservation on thermal fluctuations in the vicinity of a critical point. For that we consider a finite interacting system, which exchanges particles with a finite reservoir (thermostat), comprising a statistical ensemble that is distinct from the common canonical and grand...

We present different methods of unsupervised learning which can be used for outlier detection in high energy nuclear collisions. The UrQMD model is used to generate the bulk background of events as well as different variants of outlier events which may result from misidentified centrality or detector malfunctions. The methods presented here can be...

Using deep convolutional neural network (CNN), the nature of the QCD transition can be identified from the final-state pion spectra from hybrid model simulations of heavy-ion collisions that combines a viscous hydrodynamic model with a hadronic cascade “after-burner”. Two different types of equations of state (EoS) of the medium are used in the hyd...

We investigate simultaneous effects of finite system size and global charge conservation on thermal fluctuations in the vicinity of a critical point. For that we consider a finite interacting system which exchanges particles with a finite reservoir (thermostat), comprising a statistical ensemble that is distinct from the common canonical and grand...

The properties of compact stars and in particular the existence of twin star solutions are investigated within an effective model that is constrained by lattice QCD thermodynamics. The model is modified at large baryon densities to incorporate a large variety of scenarios of first order phase transitions to a phase of deconfined quarks. This is ach...