<p>In this study, the chemical freeze-out of hadrons, including light- and strange-flavor particles and light nuclei, produced in Au+Au collisions at the Relativistic Heavy Ion Collider (RHIC), was investigated. Using the Thermal-FIST thermodynamic statistical model, we analyzed various particle sets: those inclusive of light nuclei, those exclusive to light nuclei, and those solely comprising light nuclei. We determined the chemical freeze-out parameters at <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="41365_2025_1661_Article_IEq1.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="63" /> </InlineMediaObject> <EquationSource Format="TEX">\(\sqrt{s_\text {NN}}=\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msqrt> <msub> <mi>s</mi> <mtext>NN</mtext> </msub> </msqrt> <mo>=</mo> </mrow> </math></EquationSource> </InlineEquation> 7.7–200 GeV and four different centralities. A significant finding was the decrease in the chemical freeze-out temperature <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="41365_2025_1661_Article_IEq2.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="23" /> </InlineMediaObject> <EquationSource Format="TEX">\(T_{\text {ch}}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>T</mi> <mtext>ch</mtext> </msub> </math></EquationSource> </InlineEquation> with light-nuclei inclusion, with an even more pronounced reduction when considering light-nuclei yields exclusively. This suggests that light-nuclei formation occurs at a later stage in the system’s evolution at RHIC energies. We present parameterized formulas that describe the energy dependence of <InlineEquation ID="IEq3"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="41365_2025_1661_Article_IEq3.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="23" /> </InlineMediaObject> <EquationSource Format="TEX">\(T_{\text {ch}}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>T</mi> <mtext>ch</mtext> </msub> </math></EquationSource> </InlineEquation> and the baryon chemical potential <InlineEquation ID="IEq4"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="41365_2025_1661_Article_IEq4.gif" Format="GIF" Height="12" Rendition="HTML" Resolution="72" Type="Linedraw" Width="21" /> </InlineMediaObject> <EquationSource Format="TEX">\(\mu _\text {B}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>μ</mi> <mtext>B</mtext> </msub> </math></EquationSource> </InlineEquation> for three distinct particle sets in central Au+Au collisions at RHIC energies. Our results reveal at least three distinct <InlineEquation ID="IEq5"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="41365_2025_1661_Article_IEq5.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="23" /> </InlineMediaObject> <EquationSource Format="TEX">\(T_{\text {ch}}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>T</mi> <mtext>ch</mtext> </msub> </math></EquationSource> </InlineEquation> at RHIC energies correspond to different freeze-out hypersurfaces: a light-flavor freeze-out temperature of <InlineEquation ID="IEq6"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="41365_2025_1661_Article_IEq6.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="19" /> </InlineMediaObject> <EquationSource Format="TEX">\(T_\text {L}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>T</mi> <mtext>L</mtext> </msub> </math></EquationSource> </InlineEquation> = 150.2±6 MeV, a strange-flavor freeze-out temperature <InlineEquation ID="IEq7"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="41365_2025_1661_Article_IEq7.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="16" /> </InlineMediaObject> <EquationSource Format="TEX">\(T_\text {s}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>T</mi> <mtext>s</mtext> </msub> </math></EquationSource> </InlineEquation> = 165.1±2.7 MeV, and a light-nuclei freeze-out temperature <InlineEquation ID="IEq8"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="41365_2025_1661_Article_IEq8.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="21" /> </InlineMediaObject> <EquationSource Format="TEX">\(T_{\text {ln}}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>T</mi> <mtext>ln</mtext> </msub> </math></EquationSource> </InlineEquation> = 141.7±1.4 MeV. Notably, at the Large Hadron Collider (LHC) Pb+Pb 2.76 TeV, the expected lower freeze-out temperature for light nuclei was not observed; instead, the <InlineEquation ID="IEq9"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="41365_2025_1661_Article_IEq9.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="23" /> </InlineMediaObject> <EquationSource Format="TEX">\(T_{\text {ch}}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>T</mi> <mtext>ch</mtext> </msub> </math></EquationSource> </InlineEquation> for light nuclei was found to be approximately 10 MeV higher than that for light-flavor hadrons.</p>

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Effect of light nuclei on chemical freeze-out parameters at RHIC energies

  • Ning Yu,
  • Zu-Man Zhang,
  • Hong-Ge Xu,
  • Min-Xuan Song

摘要

In this study, the chemical freeze-out of hadrons, including light- and strange-flavor particles and light nuclei, produced in Au+Au collisions at the Relativistic Heavy Ion Collider (RHIC), was investigated. Using the Thermal-FIST thermodynamic statistical model, we analyzed various particle sets: those inclusive of light nuclei, those exclusive to light nuclei, and those solely comprising light nuclei. We determined the chemical freeze-out parameters at \(\sqrt{s_\text {NN}}=\) s NN = 7.7–200 GeV and four different centralities. A significant finding was the decrease in the chemical freeze-out temperature \(T_{\text {ch}}\) T ch with light-nuclei inclusion, with an even more pronounced reduction when considering light-nuclei yields exclusively. This suggests that light-nuclei formation occurs at a later stage in the system’s evolution at RHIC energies. We present parameterized formulas that describe the energy dependence of \(T_{\text {ch}}\) T ch and the baryon chemical potential \(\mu _\text {B}\) μ B for three distinct particle sets in central Au+Au collisions at RHIC energies. Our results reveal at least three distinct \(T_{\text {ch}}\) T ch at RHIC energies correspond to different freeze-out hypersurfaces: a light-flavor freeze-out temperature of \(T_\text {L}\) T L = 150.2±6 MeV, a strange-flavor freeze-out temperature \(T_\text {s}\) T s = 165.1±2.7 MeV, and a light-nuclei freeze-out temperature \(T_{\text {ln}}\) T ln = 141.7±1.4 MeV. Notably, at the Large Hadron Collider (LHC) Pb+Pb 2.76 TeV, the expected lower freeze-out temperature for light nuclei was not observed; instead, the \(T_{\text {ch}}\) T ch for light nuclei was found to be approximately 10 MeV higher than that for light-flavor hadrons.