arXiv subjects

Kevin P. Pala

Publications and source records attributed to Kevin P. Pala.

4 recordsLinked to original sources

arXiv2026

Studying the QCD Matter produced in Heavy-Ion Collisions using the MUSES Calculation Engine

The equation of state of hot and dense matter is essential for describing heavy-ion collisions at all collision energies. Here, we explore the capabilities of the latest version of the MUSES Calculation Engine, $\textit{Calliope}$, focusing on software modules and workflows that compute the equation of state and observable properties of the matter produced in heavy-ion collisions. These include several equations of state, ranging from first-principles lattice QCD to phenomenological approaches, with or without a critical point, and with phase-space dimensionality ranging from two dimensions defined by temperature $T$ and baryon chemical potential $\mu_B$, to four dimensions after the addition of strangeness and electric-charge chemical potentials $\mu_S$ and $\mu_Q$. We also discuss modules that provide additional thermodynamic quantities and observables relevant for heavy-ion modeling, including elements of the pressure Hessian matrix and transport coefficients. Workflow examples are constructed that merge two equations of state thermodynamically consistently to extend phase-diagram coverage, and feed the results into an equation of state inverter to produce inputs suitable for hydrodynamic simulations. Finally, we apply this framework to perform a relativistic viscous hydrodynamic simulation with equations of state with an extended $T$ and $\mu_B$ coverage and a movable critical point, including effects from transport coefficients that phenomenologically encode critical scaling, at collision energies $\sqrt{s_{NN}}=7.7, 19.6$, and $39$ GeV.

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arXiv2025

NuclearConfectionery: Multi-stage Simulation Framework for Modeling Relativistic Heavy-ion Collisions

We present the NuclearConfectionery, a modular framework for simulating the full dynamical evolution of relativistic heavy-ion collisions. Its core hydrodynamic module, CCAKE 2.0, represents a major advance over previous SPH-based relativistic hydrodynamic codes. CCAKE 2.0 simultaneously evolves energy-momentum and multiple conserved charges (B, S, Q) with a four-dimensional equation of state, and can be run in either Cartesian or hyperbolic coordinates, enabling consistent simulations from the RHIC Beam Energy Scan to LHC energies. We have implemented a particlization module that supports global BSQ charge conservation on the freeze-out surface; the resulting hadron ensemble is then propagated through a hadronic transport afterburner. A source term is included in the equations of motion to couple jets to the fluid, allowing simultaneous bulk and hard-probe evolution or, alternatively, for stopped baryons at low beam energies. The framework offers flexible choices of equations of motion (Israel-Stewart, DNMR, ADNH) and transport coefficients, along with GPU-ready performance via Kokkos/Cabana, offline equation of state inversion for 4D tables, and containerized portability. We validate the code with semi-analytical benchmarks (including BSQ Gubser and Landau-Khalatnikov solutions) and extensive convergence studies. The NuclearConfectionery provides a user-friendly, high-performance, open-source tool for event-by-event simulations across collision energies, offering flexibility to study QCD matter at both vanishing and finite densities.

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arXiv2025

Nuclear Physics Confronts Relativistic Collisions Of Isobars

High-energy collisions involving the $A=96$ isobars $^{96}$Zr and $^{96}$Ru have been performed in 2018 at Brookhaven National Laboratory's Relativistic Heavy Ion Collider (RHIC) as a means to search for the chiral magnetic effect in QCD. This would manifest itself as specific deviations from unity in the ratio of observables taken between $^{96}$Zr+$^{96}$Zr and $^{96}$Ru+$^{96}$Ru collisions. Measurements of such ratios (released at the end of 2021) indeed reveal deviations from unity, but these are primarily caused by the two collided isobars having different radial profiles and intrinsic deformations. To make progress in understanding RHIC data, nuclear physicists across the energy spectrum gathered in Heidelberg in 2022 as part of an EMMI Rapid Reaction Task Force (RRTF) to address the following question. Does the combined effort of low-energy nuclear structure physics and high-energy heavy-ion physics enable us to understand the observations made in isobar collisions at RHIC?

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arXiv2024

Impact of the pre-equilibrium phase for the determination of nuclear geometry in high-energy isobar collisions

Ultrarelativistic isobar collisions have been proposed as a useful tool to investigate nuclear structure. These systems are not created in equilibrium, rather undergo a pre-thermalization stage. In this stage, some of the initial structure information may be lost and additional effects introduced. The objective of this paper is to study this possibility in the extreme case of a "free-streaming" pre-equilibrium stage. We do this by computing estimators for ratios of various measured (or measurable) quantities (elliptic and triangular flows, mean transverse momentum and associated cumulants, correlators between elliptic or triangular flows and mean transverse momentum, symmetric cumulant and two-plane correlator) and study their sensitivity to the duration of the free-streaming stage. We find that the correlators between elliptic or triangular flows and mean transverse momentum, the so-called $ρ_2$ and $ρ_3$, are indeed sensitive to the duration of the free-streaming stage and that the normalized symmetric cumulant, $\varepsilon NSC(2,3)$ might also depend on this duration.

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