<p>Drag and diffusion coefficients of the heavy quarks (HQs), such as charm and bottom, are one of the prime tools for discerning the properties of the deconfined quantum chromo-dynamics (QCD) medium created in heavy-ion collision experiments. The innate nonperturbative nature of the QCD medium renders it imperative to estimate the transport coefficients in that domain. The present work evaluates the drag and diffusion coefficients of the moving HQs interacting with the medium particles via two-body collisional and three-body radiative processes to the first order in opacity by employing the Gribov mechanism for the nonperturbative regime. We proffer the latest results of the HQ transport coefficients computed for the nonperturbative and noneikonal gluon radiation off the HQs. The calculations show significant increments of the transport coefficients with the increasing noneikonality by juxtaposing the results with those of the perturbative and eikonal regions. We hope to shed fresh light on explaining the experimental data on the nuclear modification factor <math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>R</mi><mrow><mi>A</mi><mi>A</mi></mrow></msub></math> and the elliptic flow <math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>v</mi><mn>2</mn></msub></math> of the HQs by advocating for the importance of the noneikonality of the gluon radiation off the HQs.</p>

India

Surasree Mazumder

Natasha Sharma

Lokesh Kumar

Transport coefficients of the heavy quark in the domain of the nonperturbative and noneikonal gluon radiation

We study the production of pions, kaons, and (anti)protons using a multiphase transport (AMPT) model in <math><mrow><mi>Au</mi><mo>+</mo><mi>Au</mi></mrow></math> collisions at <math><mrow><msqrt><msub><mi>s</mi><mrow><mi>N</mi><mi>N</mi></mrow></msub></msqrt><mo>=</mo></mrow></math> 7.7, 27, and 200 GeV. We present the centrality and energy dependence of various bulk observables such as invariant yields as a function of transverse momentum <math><msub><mi>p</mi><mi>T</mi></msub></math>, particle yields <math><mrow><mi>d</mi><mi>N</mi><mo>/</mo><mi>d</mi><mi>y</mi></mrow></math>, average transverse momentum <math><mrow><mo>〈</mo><msub><mi>p</mi><mi>T</mi></msub><mo>〉</mo></mrow></math>, and various particle ratios, and compare them with experimental data. Both default and string melting (SM) versions of the AMPT model are used with three different sets of initial conditions. We observe that neither the default nor the SM version of the model could consistently describe the centrality dependence of all observables at the above energies with any one set of initial conditions. The energy dependence behavior of the experimental observables for 0–5% central collisions is in general better described by the default AMPT model using the modified hijing parameters for Lund string fragmentation and 3 mb parton scattering cross section. In addition, the kaon production as well as the <math><mrow><mi>K</mi><mo>/</mo><mi>π</mi></mrow></math> ratio at 7.7 GeV are underpredicted by the AMPT model.

Abhirikshma Nandi

Constraining the particle production mechanism in <math><mrow><mi>Au</mi><mo>+</mo><mi>Au</mi></mrow></math> collisions at <math><mrow><msqrt><msub><mi>s</mi><mrow><mi>N</mi><mi>N</mi></mrow></msub></msqrt><mo>=</mo><mn>7.7</mn></mrow></math>, 27, and 200 GeV using a multiphase transport model

Coalescence has long been used to describe the production of light (anti)nuclei in heavy-ion collisions. The same underlying mechanism may also exist in jets when a proton and a neutron are close enough in phase space to form a deuteron. We model deuteron production in jets by applying an afterburner, which uses a coalescence mechanism to form deuterons from protons and neutrons produced in pythia for <math><mi>p</mi></math>+<math><mi>p</mi></math> collisions at a center of mass energy <math><mrow><msqrt><mi>s</mi></msqrt><mo>=</mo><mn>7</mn></mrow></math> TeV. pythia provides a reasonable description of the proton spectra and the shape of the deuteron spectrum predicted by the afterburner is in agreement with the data. We show that the rise in the coalescence parameter <math><msub><mi>B</mi><mn>2</mn></msub></math> with momentum observed in data is consistent with coalescence in jets. We show that dihadron correlations can be used to separate the contributions from the jet and the underlying event. This model predicts that the conditional coalescence parameter in the jetlike correlation should be independent of the trigger momentum.

United States

Tony Perez

Andy Castro

Christine Nattrass

Methods for separation of deuterons produced in the medium and in jets in high-energy collisions

The ALICE data on light flavor hadron production obtained in p–Pb collisions at $$\sqrt{s_{NN}} = 5.02$$ <math><mrow><msqrt><msub><mi>s</mi><mrow><mi>NN</mi></mrow></msub></msqrt><mo>=</mo><mn>5.02</mn></mrow></math>  TeV are studied in the thermal model using the canonical approach with exact strangeness conservation. The chemical freeze-out temperature is independent of centrality except for the lowest multiplicity bin, with values close to 160 MeV but consistent with those obtained in Pb–Pb collisions at $$\sqrt{s_{NN}} = 2.76$$ <math><mrow><msqrt><msub><mi>s</mi><mrow><mi>NN</mi></mrow></msub></msqrt><mo>=</mo><mn>2.76</mn></mrow></math>  TeV. The value of the strangeness non-equilibrium factor $$\gamma _s$$ <math><msub><mi>γ</mi><mi>s</mi></msub></math>  is slowly increasing with multiplicity from 0.9 to 0.96, i.e. it is always very close to full chemical equilibrium.

South Africa

Jean Cleymans

Thermal model description of p–Pb collisions at $$\sqrt{s_{NN}} = 5.02$$ <math><mrow><msqrt><msub><mi>s</mi><mrow><mi>NN</mi></mrow></msub></msqrt><mo>=</mo><mn>5.02</mn></mrow></math>  TeV

We review the chemical and kinetic freeze-out conditions in high energy heavy-ion collisions for AGS, SPS, RHIC, and LHC energies. Chemical freeze-out parameters are obtained using produced particle yields in central collisions while the corresponding kinetic freeze-out parameters are obtained using transverse momentum distributions of produced particles. For chemical freeze-out, different freeze-out scenarios are discussed such as single and double/flavor dependent freeze-out surfaces. Kinetic freeze-out parameters are obtained by doing hydrodynamic inspired blast wave fit to the transverse momentum distributions. The beam energy and centrality dependence of transverse energy per charged particle multiplicity are studied to address the constant energy per particle freeze-out criteria in heavy-ion collisions.

Bedangadas Mohanty

Sandeep Chatterjee

Sabita Das

D. Mishra

Raghunath Sahoo

Freeze-Out Parameters in Heavy-Ion Collisions at AGS, SPS, RHIC, and LHC Energies