arXiv subjects

Ronald Scaria

Publications and source records attributed to Ronald Scaria.

7 recordsLinked to original sources

arXiv2024

Dynamics of Hot QCD Matter 2024 -- Bulk Properties

The second Hot QCD Matter 2024 conference at IIT Mandi focused on various ongoing topics in high-energy heavy-ion collisions, encompassing theoretical and experimental perspectives. This proceedings volume includes 19 contributions that collectively explore diverse aspects of the bulk properties of hot QCD matter. The topics encompass the dynamics of electromagnetic fields, transport properties, hadronic matter, spin hydrodynamics, and the role of conserved charges in high-energy environments. These studies significantly enhance our understanding of the complex dynamics of hot QCD matter, the quark-gluon plasma (QGP) formed in high-energy nuclear collisions. Advances in theoretical frameworks, including hydrodynamics, spin dynamics, and fluctuation studies, aim to improve theoretical calculations and refine our knowledge of the thermodynamic properties of strongly interacting matter. Experimental efforts, such as those conducted by the ALICE and STAR collaborations, play a vital role in validating these theoretical predictions and deepening our insight into the QCD phase diagram, collectivity in small systems, and the early-stage behavior of strongly interacting matter. Combining theoretical models with experimental observations offers a comprehensive understanding of the extreme conditions encountered in relativistic heavy-ion and proton-proton collisions.

nucl-th↗

arXiv2023

Proton number cumulants in a modified van der Waals hadron resonance gas

An estimate of the proton number cumulants in the hadronic matter is presented considering a van der Waals-type interaction between the constituent particles. We argue that the attractive and repulsive parameters in the VDW hadron resonance gas (VDWHRG) model change as functions of baryochemical potential ($\mu_{B}$) and temperature ($T$). This, in turn, affects the estimation of thermodynamic properties and, consequently, the conserved charge fluctuations. We employ a simple parametrization to bring in the center-of-mass energy ($\sqrt{s_{\rm NN}}$) dependence on temperature and baryochemical potential and then estimate the proton number cumulants with the modified approach. The modified van der Waals hadron resonance gas model (MVDWHRG) explains the existing experimental data very well.

hep-ph↗

arXiv2023

Energy flow in ultra-high energy cosmic ray interactions as a probe of thermalization: a potential solution to the muon puzzle

Signatures of the formation of a strongly interacting thermalized matter of partons have been observed in nucleus-nucleus, proton-nucleus, and high-multiplicity proton-proton collisions at LHC energies. Strangeness enhancement in such ultra-relativistic heavy-ion collisions is considered to be a consequence of this thermalized phase, known as quark-gluon plasma (QGP). Simultaneously, proper modeling of hadronic energy fraction in interactions of ultra-high energy cosmic rays (UHECR) has been proposed as a solution for the muon puzzle, an unexpected excess of muons in air showers. These interactions have center-of-mass collision energies of the order of energies attained at the LHC or even higher, indicating that the possibility of a thermalized partonic state cannot be overlooked in UHECR-air interactions. This work investigates the hadronic energy fraction and strangeness enhancement to explore QGP-like phenomena in UHECR-air interactions using various high-energy hadronic models. A core-corona system with a thermalized core undergoing statistical hadronization is considered through the EPOS LHC model. In contrast, PYTHIA 8, QGSJET II-04, and SYBILL 2.3d consider string fragmentation without thermalization. We have found that EPOS LHC gives a better description of strangeness enhancement as compared to other models. We conclude that adequately treating all the relevant effects and further retuning the models is necessary to explain the observed effects.

hep-ph↗

arXiv2022

Applicability of Hydrodynamics in Hadronic Phase of Heavy-Ion Collisions

The hadronic phase and its dynamics in relativistic heavy-ion collisions are topics of immense discussion. The hadronic phase contains various massive hadrons with an abundance of the lightest hadron, i.e., $\pi$-mesons (pions). In this paper, we consider that pions are in thermal equilibrium in the hadronic phase and use second-order viscous hydrodynamics for a medium of massive pions to obtain its expansion to the boundary of the kinetic freeze-out. We achieve the kinetic freeze-out boundary with the Knudsen number $Kn>1$ limit. When this condition is met, hydrodynamics expansion breaks down, and the mean free path becomes sufficiently large in comparison with the system size so that the particle yields are preserved. Further, we investigate the effect of the massive fluid on the resonance particle yields, including re-scattering and regeneration, along with the natural decay widths of the resonances. The resonances can play an essential role in determining the characteristics of the hadronic phase as they have sufficiently small lifetimes, which may be comparable to the hadronic phase lifetime. In the current study, we predict the hadronic phase lifetime, which is further used to determine the $K^*(892)^0/K$, $\phi(1020)/K$, and $\rho(770)^0/\pi$ yield ratios at the kinetic freeze-out. We calculate these ratios as a function of charged particle multiplicity and transverse momentum and compare the findings with experimental data. Our calculations qualitatively agree with the experimental data, indicating a possible hydrodynamical evolution of the hadronic phase.

hep-ph↗

arXiv2022

Conductivity, diffusivity, and violation of Wiedemann-Franz Law in a hadron resonance gas with van der Waals interactions

In this work, a hadron resonance gas under van der Waals (VDW) interactions has been studied. Both attractive and repulsive interactions between the meson-meson and (anti)baryon-(anti)baryon have been taken into consideration. Various transport properties such as electrical conductivity ($\sigma_{\rm el}$) and thermal conductivity ($\kappa_{\rm th}$) have been estimated by solving the Boltzmann transport equation under the relaxation time approximation. The effect of baryochemical potential ($\mu_{\rm B}$) and temperature is also explicitly explored for the mentioned observables. Comparisons have been made with the results obtained from other existing theoretical models. We observe the violation of Wiedemann-Franz law in a hadron resonance gas at a high-temperature regime. The corresponding diffusivities have also been estimated, which can help us to understand the system in a better way.

hep-ph↗

arXiv2022

Fluidity of the system produced in relativistic pp and heavy-ion collisions: Hadron resonance gas model approach

We have estimated the dimensionless parameters such as Reynolds number ($Re$), Knudsen number ($Kn$) and Mach number ($Ma$) for a multi-hadron system by using the excluded volume hadron resonance gas (EVHRG) model along with Hagedorn mass spectrum to include higher resonances in the system. The size dependence of these parameters indicate that the system formed in proton+proton collisions may achieve thermal equilibrium making it unsuitable as a benchmark to analyze the properties of the system produced in heavy ion collisions at similar energies. While the magnitude of $Kn$ can be used to study the degree of thermalization and applicability of inviscid hydrodynamics, the variations of $Re$ and $Ma$ with temperature ($T$) and baryonic chemical potential ($\mu_B$) assist to understand the change in the nature of the flow in the system. Indeed the nature of flow changes from laminar to turbulent as $Re$ increases and the system is characterized as incompressible for low $Ma (<<1)$ and compressible for larger $Ma$. $Ma$ can also be used to understand whether the flow is subsonic or supersonic.

hep-ph↗

arXiv2021

Exploring the effect of hadron cascade-time on particle production in Xe+Xe collisions at $\sqrt{s_{\rm{NN}}}$ = 5.44 TeV through a multi-phase transport model

Heavy-ion collisions at ultra-relativistic energies provide extreme conditions of energy density and temperature to produce a deconfined state of quarks and gluons. Xenon (Xe) being a deformed nucleus further gives access to the effect of initial geometry on final state particle production. This study focuses on the effect of nuclear deformation and hadron cascade-time on the particle production and elliptic flow using A Multi-Phase Transport (AMPT) model in Xe+Xe collisions at $\sqrt{s_{\rm NN}}$ = 5.44 TeV. We explore the effect of hadronic cascade-time on identified particle production through the study of $p_{\rm T}$-differential particle ratios. The effect of hadronic cascade-time on the generation of elliptic flow is studied by varying the cascade-time between 5 and 25 fm/$c$. This study shows the final state interactions among particles generate additional anisotropic flow with increasing hadron cascade-time, especially at very low and high-$p_{\rm T}$.

hep-ph↗