<p>This study investigates the evolution and dissociation dynamics of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>c</mi><mover accent="true"><mi>c</mi><mo stretchy="false">¯</mo></mover></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>b</mi><mover accent="true"><mi>b</mi><mo stretchy="false">¯</mo></mover></math> pairs within the preequilibrium, gluon-dominated stage of high energy nuclear collisions. An attractive potential made of a perturbative Coulomb-like term and of a confining term is used to simulate the attractive strong force in the pairs. Besides, we implement the interaction of the pairs with the evolving glasma fields by virtue of the Wong equations. The interaction with the classical color fields dominates the dynamics, causing an increase in pair separation and subsequent dissociation. The observed finite probability of dissociation for these states reveals the intricate interplay between quantum chromodynamics (QCD) dynamics and the suppression of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>c</mi><mover accent="true"><mi>c</mi><mo stretchy="false">¯</mo></mover></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>b</mi><mover accent="true"><mi>b</mi><mo stretchy="false">¯</mo></mover></math> states during the preequilibrium stage. The research highlights differences between <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>c</mi><mover accent="true"><mi>c</mi><mo stretchy="false">¯</mo></mover></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>b</mi><mover accent="true"><mi>b</mi><mo stretchy="false">¯</mo></mover></math> pairs, revealing the role of quark flavor in the dissociation process. Dissociation spectra analysis indicates a peak shift toward higher momentum, reflecting a slight energy gain by the pairs. This investigation provides valuable insights into the complex dynamics of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>c</mi><mover accent="true"><mi>c</mi><mo stretchy="false">¯</mo></mover></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>b</mi><mover accent="true"><mi>b</mi><mo stretchy="false">¯</mo></mover></math> pairs in the glasma, which may help in better interpretation of experimental results on further integration with subsequent phases of the created matter.</p>

India

 Pooja

Mohammad Yousuf Jamal

Partha Pratim Bhaduri

Italy

Marco Ruggieri

Santosh K. Das

<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>c</mi><mover accent="true"><mrow><mi>c</mi></mrow><mrow><mo stretchy="false">¯</mo></mrow></mover></mrow></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>b</mi><mover accent="true"><mrow><mi>b</mi></mrow><mrow><mo stretchy="false">¯</mo></mrow></mover></mrow></math> suppression in the glasma

We investigate the effect of flow fluctuations, incorporated in non-boost-invariant blast-wave model, on kinetic freeze-out parameters of identified hadrons in low energy relativistic heavy-ion collisions. For the purpose of this study, we use the transverse momentum spectra of the identified hadrons produced in central Pb–Pb collisions, at CERN Super Proton Synchrotron energies ranging from <math><mrow><msub><mi>E</mi><mi>lab</mi></msub><mo>=</mo><mn>20</mn><mi>A</mi><mtext>–</mtext><mn>158</mn><mi>A</mi></mrow></math> GeV, and analyze them within a modified non-boost-invariant blast wave model. We perform simultaneous fits of the transverse momentum spectra for light hadrons <math><mo>(</mo><msup><mi>π</mi><mo>−</mo></msup></math>, <math><msup><mi>K</mi><mo>±</mo></msup><mo>,</mo></math> <math><mi>p</mi><mo>)</mo></math> and heavy strange hadrons <math><mo>(</mo><mi>Λ</mi><mo>,</mo></math> <math><mover><mi>Λ</mi><mo>¯</mo></mover><mo>,</mo></math> <math><mi>ϕ</mi><mo>,</mo></math> <math><msup><mi>Ξ</mi><mo>±</mo></msup><mo>,</mo></math> <math><msup><mi>Ω</mi><mo>±</mo></msup><mo>)</mo></math> separately. We also fit the transverse momentum spectra of charmonia <math><mrow><mo>(</mo><mi>J</mi><mo>/</mo><mi>Ψ</mi><mo>,</mo></mrow></math> <math><msup><mi>Ψ</mi><mo>′</mo></msup><mo>)</mo></math> at <math><mrow><msub><mi>E</mi><mi>lab</mi></msub><mo>=</mo><mn>158</mn><mi>A</mi></mrow></math> GeV. Our findings suggest that the inclusion of flow fluctuations enhances kinetic freeze-out temperature in case of light and heavy strange hadrons and reduces the corresponding transverse flow velocities. Moreover, we find that the kinetic freeze-out parameters of the charmonia at <math><mrow><msub><mi>E</mi><mi>lab</mi></msub><mo>=</mo><mn>158</mn><mi>A</mi></mrow></math> GeV are least affected by inclusion of flow fluctuations. Based on this, we make predictions which can provide further insights on the role of flow fluctuations in relativistic heavy-ion collisions.

JINR

Sudhir Pandurang Rode

Amaresh Jaiswal

Flow fluctuations and kinetic freeze-out of identified hadrons at energies available at the CERN Super Proton Synchrotron

We analyze the relative yields of different bottomonia and charmonia states produced in Pb-Pb, <math><mi>p</mi><mtext>−</mtext><mi>Pb</mi></math>, and high multiplicity <math><mi>p</mi><mtext>−</mtext><mi>p</mi></math> collisions at the CERN Large Hadron Collider, within a semiclassical grand canonical ensemble approach. The underlying assumption is the early thermalization and subsequent freeze-out of these heavy hadrons resulting in their chemical freeze-out at a temperature of approximately <math><mrow><mn>230</mn><mspace width="4pt"></mspace><mi>MeV</mi></mrow></math>, significantly higher than that of light and strange hadrons. The systematic dependence of the freeze-out temperature on the collision centrality is also investigated in detail.

Deekshit Kumar

Nachiketa Sarkar

Examination of thermalization of quarkonia at energies available at the CERN Large Hadron Collider

We study the mass-dependent hierarchy of kinetic freeze-out parameters of hadrons in low-energy heavy-ion collisions. For this purpose, the transverse momentum and rapidity spectra of the identified hadrons produced in central <math><mi>Pb</mi><mo>+</mo><mi>Pb</mi></math> collisions, available at super proton synchrotron energies ranging from <math><mrow><msub><mi>E</mi><mtext>Lab</mtext></msub><mo>=</mo><mn>20</mn><mi>A</mi><mo>–</mo><mn>158</mn><mi>A</mi></mrow></math> GeV, are analyzed within a generalized non-boost-invariant blast-wave model. We consider separate simultaneous fits for light hadrons (<math><msup><mi>π</mi><mo>−</mo></msup><mo>,</mo><mo> </mo><msup><mi>K</mi><mo>±</mo></msup></math>) and heavy strange hadrons (<math><mi>Λ</mi><mo>,</mo><mo> </mo><mover><mi>Λ</mi><mo>¯</mo></mover><mo>,</mo><mo> </mo><mi>ϕ</mi><mo>,</mo><mo> </mo><msup><mi>Ξ</mi><mo>±</mo></msup><mo>,</mo><mo> </mo><msup><mi>Ω</mi><mo>±</mo></msup></math>), for which the transverse momentum spectra as well as rapidity spectra are available. We also perform a separate fit to transverse momentum spectra of charmonia (<math><mrow><mi>J</mi><mo>/</mo><mi>Ψ</mi></mrow><mo>,</mo><mo> </mo><msup><mi>Ψ</mi><mo>′</mo></msup></math>) at <math><mrow><mn>158</mn><mi>A</mi></mrow></math> GeV collisions. We find a clear mass-dependent hierarchy in the fitted kinetic freeze-out parameters. Further, we study the rapidity spectra using analytical Landau flow solution for nonconformal systems. We find that the fitted value of sound velocity in the medium also shows a similar hierarchy.

Ankhi Roy

Hierarchy of kinetic freeze-out parameters in low-energy heavy-ion collisions

We study the role of anisotropic escape in generating the elliptic flow of bottomonia produced in ultrarelativistic heavy-ion collisions. We implement temperature-dependent decay widths for the various bottomonium states to calculate their survival probability when traversing through the anisotropic hot medium formed in noncentral collisions. We employ the recently developed <math><mrow><mn>3</mn><mo>+</mo><mn>1</mn></mrow></math>-dimensional quasiparticle anisotropic hydrodynamic simulation to model the space-time evolution of the quark-gluon plasma. We provide a quantitative prediction for the transverse momentum dependence of bottomonium elliptic flow and the nuclear modification factor for <math><mrow><mi>Pb</mi><mspace width="0.16em"></mspace><mo>+</mo><mspace width="0.16em"></mspace><mi>Pb</mi></mrow></math> collisions in <math><mrow><msqrt><msub><mi>s</mi><mi>NN</mi></msub></msqrt><mo>=</mo><mn>2.76</mn></mrow></math> TeV at the CERN Large Hadron Collider.

Germany

Nicolas Borghini

United States

Michael Strickland

Anisotropic escape mechanism and elliptic flow of bottomonia

We study the effect of an anisotropic escape mechanism on elliptic flow in relativistic heavy-ion collisions. We use the Glauber model to generate initial conditions and ignore hydrodynamic expansion in the transverse direction. We employ the Beer-Lambert law to allow for the transmittance of produced hadrons in the medium and calculate the anisotropy generated due to the suppression of particles traversing through the medium. To separate non-flow contribution due to surface bias effects, we ignore hydrodynamic expansion in the transverse direction and consider purely longitudinal boost-invariant expansion. We calculate the transverse momentum dependence of elliptic flow, generated from an anisotropic escape mechanism due to surface bias effects, for various centralities in <math><mrow><msqrt><msub><mi>s</mi><mrow><mi>N</mi><mi>N</mi></mrow></msub></msqrt><mo>=</mo><mn>200</mn></mrow></math> GeV <math><mrow><mi>Au</mi><mo>+</mo><mi>Au</mi></mrow></math> collisions at the Relativistic Heavy Ion Collider and <math><mrow><msqrt><msub><mi>s</mi><mrow><mi>N</mi><mi>N</mi></mrow></msub></msqrt><mo>=</mo><mn>2.76</mn></mrow></math> TeV <math><mrow><mi>Pb</mi><mo>+</mo><mi>Pb</mi></mrow></math> collisions at the Large Hadron Collider. We find that the surface bias effects make a sizable contribution to the total elliptic flow observed in heavy-ion collisions, indicating that the viscosity of the QCD matter extracted from hydrodynamic simulations may be underestimated.