Harmonic flow correlations in Au+Au reactions at 1.23 AGeV: a new testing ground for the equation-of-state and expansion geometry

Reichert, Tom; Steinheimer, Jan; Herold, C.; Limphirat, A.; Bleicher, Marcus

doi:10.1140/epjc/s10052-022-10480-0

Cited by 10 publications

(5 citation statements)

References 49 publications

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“…Here, Fig. 1 shows the first four symmetric flow coefficients v sym has a positive correlation with the longitudinal momentum and reflects the strength of the bounce off of the two incoming nuclei as was discussed in detail in [23] and we observe as expected that with a stiffer equation of state the bounce off becomes more pronounced due to larger pressure (density) gradients. The elliptic flow v sym 2 is negative around zero longitudinal momenta and exhibits a convex shape.…”

Section: Results: Momentum Dependence Of the Novel Flow Coefficientssupporting

confidence: 71%

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3-dimensional flow analysis: A novel tool to study the collision geometry and the Equation-of-State

Reichert¹,

Steinheimer²,

Bleicher³

2022

Preprint

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We propose to extend the commonly known flow analysis in the transverse px-py plane to novel flow coefficients based on the angular distribution in the px-pz and py-pz planes. The new flow coefficients, called un and wn (in addition to vn), turn out to be also highly sensitive to the nuclear Equation-of-State and can be used to explore the EoS in more detail than is possible using only vn.As an example to quantify the effect of the EoS, the Ultra-relativistic Quantum Molecular Dynamics (UrQMD) model is used to investigate 20-30% central Au+Au collisions at E lab = 1.23 AGeV.

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Section: Results: Momentum Dependence Of the Novel Flow Coefficientssupporting

confidence: 71%

“…[22]. UrQMD has been further highly successful in describing and predicting directed, elliptic, triangular as well as quadrangular flow of nucleons and light clusters [13,14] and their correlations [23].…”

Section: Model Setup and Flow Extractionmentioning

confidence: 99%

3-dimensional flow analysis: A novel tool to study the collision geometry and the Equation-of-State

Reichert¹,

Steinheimer²,

Bleicher³

2022

Preprint

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“…A recent study has shown that this approach is consistent with MST calculations for cluster production [13]. UrQMD has already been successfully applied to calculate direct and elliptic flow and higher-order flow components [5,6,14] of nucleons and light clusters in the investigated energy regime and has recently demonstrated its abilities to further describe larger clusters (t, 3 He) [15].…”

Section: Simulation Set-upmentioning

confidence: 69%

Probing system size dependence at high baryon density by systematic comparison of Ag+Ag and Au+Au reactions at 1.23A GeV

Reichert¹,

Kittiratpattana²,

Li³

et al. 2023

J. Phys. G: Nucl. Part. Phys.

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We present UrQMD predictions for the comparison of the recently measured Ag+Ag and Au+Au runs at a beam energy of $E_\mathrm{lab}$ = 1.23~$A$GeV explored by the HADES experiment. To this aim, different centrality definitions are investigated: We suggest that in the case of particle production, both systems should be compared at the same number of participating nucleons, while for a comparison of the (elliptic) flow, a selection on the initial state eccentricity - as in high energy reactions - is better suited. Generally, we find good agreement between both systems, if these centrality criteria are used. Specifically, the deuteron yields per participant and the pion to proton ratios are shown to scale with $A_\mathrm{part}$ except for very central Ag+Ag reactions due to stronger stopping in such reactions. The elliptic flow in both systems follows initial state eccentricity scaling, albeit with the opposite sign as compared to high energies, suggesting a strong relation between final flows and the initial state also at the low energies explored here. The observation of this scaling might then allow to obtain further information on the expansion properties (and the EoS) of matter at high baryon densities.

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“…After the compilation of this comparison, several updates of the transport codes used here were published or are in progress: UrQMD version 3.5 [404][405][406] was released, JAM, previously written in Fortran, was rewritten in C++ introducing several updates to the mean-field potentials in version 2.1 [407,408] and the GiBUU code in its recent version of 2021 was released. Since the models used here do not apply dedicated mechanisms for producing light clusters, we restrict the comparison to protons only.…”

Section: Transport Model Simulationsmentioning

confidence: 99%

Collective flow measurements in Gold-Gold collisions at 1.23 AGeV with HADES

Kardan

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In this thesis, the flow coefficients vn of the orders n = 1 − 6 are studied for protons and light nuclei in Au+Au collisions at Ebeam = 1.23 AGeV, equivalent to a center-of-mass energy in the nucleon-nucleon system of √sNN = 2.4 GeV. The detailed multi-differential measurement is performed with the HADES experiment at SIS18/GSI. HADES, with its large acceptance, covering almost full azimuth angle, combined with its high mass-resolution and good particle-identification capability, is well equipped to study the azimuthal flow pattern not only for protons, deuterons, and tritons but also for charged pions, kaons, the φ-mesons, electrons/positrons, as well as light nuclei like helions and alphas. The high statistics of more than seven billion Au-Au collisions recorded in April/May 2012 with HADES enables for the first time the measurement of higher order flow coefficients up to the 6th harmonic. Since the Fourier coefficient of 7th and 8th order are beyond the statistical significance only an upper bound is given. The Au+Au collision system is the largest reaction system with the highest particle multiplicities, which was measured so far with HADES. A dedicated correction method for the flow measurement had to be developed to cope with the reconstruction in-efficiencies due to occupancies of the detector system. The systematical bias of the flow measurement is studied and several sources of uncertainties identified, which mainly arise from the quality selection criteria applied to the analyzed tracks, the correction procedure for reconstruction inefficiencies, the procedures for particle identification (PID) and the effects of an azimuthally non-uniform detector acceptance. The systematic point-to-point uncertainties are determined separately for each particle type (proton, deuteron and triton), the order of the flow harmonics vn, and the centrality class. Further, the validity of the results is inspected in the range of their evaluated systematic uncertainties with several consistency checks. In order to enable meaningful comparisons between experimental observations and predictions of theoretical models, the classification of events should be well defined and in sufficiently narrow intervals of impact parameter. Part of this work included the implementation of the procedure to determine the centrality and orientation of the reaction. In the conclusion the experimental results are discussed, including various scaling properties of the flow harmonics. It is found that the ratio v4/v2 for protons and light nuclei (deuterons and tritons) at midrapidity for all centrality classes approaches values close to 0.5 at high transverse momenta, which was suggested to be indicative for an ideal hydrodynamic behaviour. A remarkable scaling is observed in the pt dependence of v2 (v4) at mid-rapidity of the three hydrogen isotopes, when dividing by their nuclear mass number A (A^2) and pt by A. This is consistent with naive expectations from nucleon coalescence, butraises the question whether this mass ordering can also be explained by a hydrodynamical-inspired approach, like the blast-wave model. The relation of v2 and v4 to the shape of the initial eccentricity of the collision system is studied. It is found that v2 is independent of centrality for all three particle species after dividing it by the averaged second order participant eccentricity v2/⟨ε2⟩. A similar scaling is shown for v4 after division by ⟨ε2⟩^2.

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Harmonic flow correlations in Au+Au reactions at 1.23 AGeV: a new testing ground for the equation-of-state and expansion geometry

Abstract: 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-periphera… Show more

Cited by 10 publications

References 49 publications

3-dimensional flow analysis: A novel tool to study the collision geometry and the Equation-of-State

3-dimensional flow analysis: A novel tool to study the collision geometry and the Equation-of-State

Probing system size dependence at high baryon density by systematic comparison of Ag+Ag and Au+Au reactions at 1.23A GeV

Collective flow measurements in Gold-Gold collisions at 1.23 AGeV with HADES

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