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Heavy-ion collisions at varying collision energies provide access to different regions of the QCD phase diagram. In particular collisions at intermediate energies are promising candidates to experimentally identify the postulated first order phase transition and critical end point. While heavy-ion collisions at low and high collision energies are theoretically well described by transport approaches and hydrodynamics+transport hybrid approaches, respectively, intermediate energy collisions remain a challenge. In this work, a modular hybrid approach, the SMASH-vHLLE-hybrid coupling 3+1D viscous hydrodynamics (vHLLE) to hadronic transport (SMASH), is introduced. It is validated and subsequently applied in Au+Au/Pb+Pb collisions between s NN = 4.3 GeV and s NN = 200.0 GeV to study the rapidity and transverse mass distributions of identified particles as well as excitation functions for dN / d y | y = 0 and ⟨ p T ⟩ . A good agreement with experimental measurements is obtained, including the baryon stopping dynamics. The transition from a Gaussian rapidity spectrum of protons at lower energies to the double-hump structure at high energies is reproduced. The centrality and energy dependence of charged particle v 2 is also described reasonably well. This work serves as a basis for further studies, e.g. systematic investigations of different equations of state or transport coefficients. [ABSTRACT FROM AUTHOR]

Abstract STAR collaboration at RHIC has recently measured the polarization of Λ hyperons in non-central heavy ion collisions in the RHIC Beam Energy Scan (BES) program. The magnitude of the polarization was found to decrease from few percents at the lowest BES energies to ≈ 0.2% at the top RHIC energy. The polarization signal has been reproduced in different hydrodynamic calculations assuming a thermodynamic spin-vorticity coupling mechanism at the Cooper-Frye hypersurface [1]. In this work an extension of our existing calculations [2] of the Λ polarization in the RHIC BES program to the top RHIC and 2.76 TeV LHC energies is presented. The longitudinal component of the Λ polarization, which is the dominant component of the polarization at the LHC energies, is discussed. Finally we show that the global polarization of Λ originates dominantly from the relativistic analogue of the classical vorticity, whereas the quadrupole longitudinal component originates from the gradients of temperature and acceleration of the medium when the Λs are produced out of the fluid. [ABSTRACT FROM AUTHOR]

In this note, we discuss the rapidity dependence of the initial and final conditions for hydrodynamic evolution as well as the resulting basic hadronic observables in heavy-ion collisions at p √SNN = 72 GeV in the framework of a viscous hydrodynamic+cascade model vHLLE+UrQMD. The resulting rapidity dependences are driven to a big extent by the initial state, which is simulated with the UrQMD cascade. The results can serve as a prediction for future experiments such as the AFTER@LHC or the BES-II program at STAR. [ABSTRACT FROM AUTHOR]

We investigate the collision energy dependence of η / s in a transport + viscous hydrodynamics hybrid model. A Bayesian analysis is performed on RHIC beam energy scan data for Au + Au collisions at s NN = 19.6 , 39, and 62.4 GeV. The resulting posterior probability distributions for the model parameters show a preference for a larger value of η / s at 19.6 GeV compared to 62.4 GeV, indicating dependence on baryon chemical potential μ B . [ABSTRACT FROM AUTHOR]

Polarization of Λ hyperons and their antiparticles is calculated in a 3 + 1 dimensional viscous hydrodynamic model with initial state from UrQMD hadron/string cascade. We find that, along with recent results from STAR, the mean polarization at fixed centrality decreases as a function of collision energy from 1.5% at s NN = 7.7 GeV to 0.2% at s NN = 200 GeV . We explore the effects which lead to such collision energy dependence, feed-down corrections and a difference between Λ and Λ ¯ . [ABSTRACT FROM AUTHOR]

Central lead-lead collisions at energies available at the CERN Large Hadron Collider (LHC) may pose a particular challenge for jet identification as multiple jets are produced per each collision event. We simulate the jet evolution in central PbPb events at √sNN=2.76GeV collision energy with the epos3 initial state, which typically contains multiple hard scatterings in each event. Therefore the partons from different jets have a significant chance to overlap in momentum space. We find that 30% of the jets with p⊥>50GeV, identified by the standard anti-k⊥ jet finding algorithm with jet cone size R=0.3, contain "intruder" particles from overlapping generator-level jets. This fraction increases with increasing beam energy and increasing R. The reconstructed momentum of the jet differs from that of the modeled jet by the loss due to jet partons which are outside of the jet cone and by the gain due to intruder partons. The sum of both may be positive or negative. These intruder partons particularly affect the radial jet momentum distribution because they contribute mostly at large angles Δr with respect to the jet center. The study stresses the importance of the jet overlap effect emerging in central lead-lead collisions at LHC energies, while being negligible in peripheral PbPb or pPb/pp collisions. [ABSTRACT FROM AUTHOR]

This report summarizes the presentations and discussions during the Rapid Reaction Task Force "Dynamics of critical fluctuations: Theory – phenomenology – heavy-ion collisions", which was organized by the ExtreMe Matter Institute EMMI and held at GSI, Darmstadt, Germany in April 2019. We address the current understanding of the dynamics of critical fluctuations in QCD and their measurement in heavy-ion collision experiments. In addition, we outline what might be learned from studying correlations in other physical systems, such as cold atomic gases. [ABSTRACT FROM AUTHOR]

We determine the probability distributions of the shear viscosity over the entropy density ratio η/s in the quark-gluon plasma formed in Au + Au collisions at √sNN=19.6,39, and 62.4GeV, using Bayesian inference and Gaussian process emulators for a model-to-data statistical analysis that probes the full input parameter space of a transport + viscous hydrodynamics hybrid model. We find the most likely value of η/s to be larger at smaller √sNN, although the uncertainties still allow for a constant value between 0.10 and 0.15 for the investigated collision energy range. [ABSTRACT FROM AUTHOR]