Description:
<jats:title>Abstract</jats:title><jats:p>We introduce a novel approach based on elastic and inelastic scattering rates to extract the hyper-surface of the chemical freeze-out from a hadronic transport model in the energy range from E<jats:inline-formula><jats:alternatives><jats:tex-math>$$_\mathrm {lab}=1.23$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML">
<mml:mrow>
<mml:msub>
<mml:mrow />
<mml:mi>lab</mml:mi>
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<mml:mo>=</mml:mo>
<mml:mn>1.23</mml:mn>
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</mml:math></jats:alternatives></jats:inline-formula> AGeV to <jats:inline-formula><jats:alternatives><jats:tex-math>$$\sqrt{s_\mathrm {NN}}=62.4$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML">
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<mml:msqrt>
<mml:msub>
<mml:mi>s</mml:mi>
<mml:mi>NN</mml:mi>
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</mml:msqrt>
<mml:mo>=</mml:mo>
<mml:mn>62.4</mml:mn>
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</mml:math></jats:alternatives></jats:inline-formula> GeV. For this study, the Ultra-relativistic Quantum Molecular Dynamics (UrQMD) model combined with a coarse-graining method is employed. The chemical freeze-out distribution is reconstructed from the pions through several decay and re-formation chains involving resonances and taking into account inelastic, pseudo-elastic and string excitation reactions. The extracted average temperature and baryon chemical potential are then compared to statistical model analysis. Finally we investigate various freeze-out criteria suggested in the literature. We confirm within this microscopic dynamical simulation, that the chemical freeze-out at all energies coincides with <jats:inline-formula><jats:alternatives><jats:tex-math>$$\langle E\rangle /\langle N\rangle \approx 1$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML">
<mml:mrow>
<mml:mo>⟨</mml:mo>
<mml:mi>E</mml:mi>
<mml:mo>⟩</mml:mo>
<mml:mo>/</mml:mo>
<mml:mo>⟨</mml:mo>
<mml:mi>N</mml:mi>
<mml:mo>⟩</mml:mo>
<mml:mo>≈</mml:mo>
<mml:mn>1</mml:mn>
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</mml:math></jats:alternatives></jats:inline-formula> GeV, while other criteria, like <jats:inline-formula><jats:alternatives><jats:tex-math>$$s/T^3=7$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML">
<mml:mrow>
<mml:mi>s</mml:mi>
<mml:mo>/</mml:mo>
<mml:msup>
<mml:mi>T</mml:mi>
<mml:mn>3</mml:mn>
</mml:msup>
<mml:mo>=</mml:mo>
<mml:mn>7</mml:mn>
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</mml:math></jats:alternatives></jats:inline-formula> and <jats:inline-formula><jats:alternatives><jats:tex-math>$$n_\mathrm {B}+n_{\bar{\mathrm {B}}}\approx 0.12$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML">
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<mml:msub>
<mml:mi>n</mml:mi>
<mml:mi>B</mml:mi>
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<mml:mo>+</mml:mo>
<mml:msub>
<mml:mi>n</mml:mi>
<mml:mover>
<mml:mrow>
<mml:mi>B</mml:mi>
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<mml:mrow>
<mml:mo>¯</mml:mo>
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</mml:mover>
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<mml:mo>≈</mml:mo>
<mml:mn>0.12</mml:mn>
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</mml:math></jats:alternatives></jats:inline-formula> fm<jats:inline-formula><jats:alternatives><jats:tex-math>$$^{-3}$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML">
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<mml:mrow />
<mml:mrow>
<mml:mo>-</mml:mo>
<mml:mn>3</mml:mn>
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</mml:math></jats:alternatives></jats:inline-formula> are limited to higher collision energies.</jats:p>