arXiv subjects

Scott Pratt

Publications and source records attributed to Scott Pratt.

At least 19 recordsLinked to original sources

arXiv2024

Theoretical description of proton-deuteron interactions using exact two-body dynamic of femtoscopic correlation method

Modeling proton-deuteron interactions is particularly challenging. Due the deuteron's large size, the interaction can extend over several femtometers. The degree to which it can be modeled as a two-body problem might also be questioned. One way to study these interactions is through femtoscopic correlation measurements of particle pairs, extracting information using available theoretical models. In this work, we examine two approaches for describing proton-deuteron correlations: the Lednicky-Lyuboshits formalism and full numerical solutions of the Schrodinger equation. Our results show that the differences between these methods are significant. Furthermore, we demonstrate that incorporating higher-order partial waves-particularly p-wave -is the essential for accurately capturing the dynamics of proton-deuteron interactions and the full potential of the strong force.

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arXiv2024

Disoriented isospin condensates in heavy-ion collisions

Anomalous neutral to charged kaon correlations measured by the ALICE collaboration have defied usual explanations. We propose that the large fluctuations could arise because of a disoriented isospin condensate where there is an imbalance between up and down condensates at the time kaons hadronize. This could happen in heavy-ion collisions when the quark condensate re-forms as the system cools and the approximate chiral symmetry of QCD is broken. Within the linear sigma model, we show that the energy cost of forming a disoriented isospin condensate is small making it very plausible.

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arXiv2024

Anomalous kaon correlations measured in Pb-Pb collisions at the LHC as evidence for the melting and refreezing of the QCD vacuum

Measurements of the dynamical correlations between neutral and charged kaons in central Pb-Pb collisions at $\sqrt{s_{NN}} = 2.76$ TeV by the ALICE Collaboration display anomalous behavior relative to conventional heavy-ion collision simulators. We consider other conventional statistical models, none of which can reproduce the magnitude and centrality dependence of the correlations. The data can be reproduced by coherent emission from domains which grow in number and volume with increasing centrality. We study the dynamical evolution of the strange quark condensate and show that the energy released during the expansion and cooling of the system may be sufficient to explain the anomaly.

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arXiv2023

Baryon Transport in Color Flux Tubes

Color flux tubes are a standard perspective from which to understand stopping in high-energy collisions. Mechanisms for baryon transport and polarization within a tube are considered here, both in regards to the the transport of baryons from the target and projectile toward mid-rapidity, and in regards to the correlations of baryon-antibaryon pairs created in the tube. The roles of tube merging and gluon radiation with a tube are emphasized.

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arXiv2023

Correlations of Conserved Quantities at Finite Baryon Density

Correlations involving the seven conserved quantities, namely energy, baryon number, electric charge, strangeness, and the three components of momentum, give rise to correlations in heavy-ion collisions. Through the utilization of a simple one-dimensional hydrodynamic model, we calculate the evolution of the entire $7\times7$ matrix of correlations as a function of relative spatial rapidity. This comprehensive analysis accounts for finite baryon density, which results in off-diagonal correlations between the charge-related quantities and the energy-momentum quantities. These correlations in coordinate space are subsequently transformed into correlations in momentum space using statistical weighting. The entire matrix of correlations is revealed to be highly sensitive to the equation of state (EoS), viscosity, and diffusivity.

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arXiv2023

Disoriented isospin condensates may be the source of anomalous kaon correlations measured in Pb-Pb collisions at $\sqrt{s_{NN}} = 2.76$ TeV

The magnitude of fluctuations between charged and neutral kaons measured by the ALICE Collaboration in heavy-ion collisions at the LHC exceeds conventional explanation. Here it is shown that if the scalar condensate, which is typically associated with chiral symmetry, is accompanied by an isospin=1 field, then the combination can produce large fluctuations where $\langle \bar{u}u\rangle \ne \langle \bar{d}d\rangle$. Hadronizing strange and anti-strange quarks might then strongly fluctuate between charged ($u\bar{s}$ or $s\bar{u}$) and neutral ($d\bar{s}$ or $s\bar{d}$) kaons.

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arXiv2023

Dense Nuclear Matter Equation of State from Heavy-Ion Collisions

The nuclear equation of state (EOS) is at the center of numerous theoretical and experimental efforts in nuclear physics. With advances in microscopic theories for nuclear interactions, the availability of experiments probing nuclear matter under conditions not reached before, endeavors to develop sophisticated and reliable transport simulations to interpret these experiments, and the advent of multi-messenger astronomy, the next decade will bring new opportunities for determining the nuclear matter EOS, elucidating its dependence on density, temperature, and isospin asymmetry. Among controlled terrestrial experiments, collisions of heavy nuclei at intermediate beam energies (from a few tens of MeV/nucleon to about 25 GeV/nucleon in the fixed-target frame) probe the widest ranges of baryon density and temperature, enabling studies of nuclear matter from a few tenths to about 5 times the nuclear saturation density and for temperatures from a few to well above a hundred MeV, respectively. Collisions of neutron-rich isotopes further bring the opportunity to probe effects due to the isospin asymmetry. However, capitalizing on the enormous scientific effort aimed at uncovering the dense nuclear matter EOS, both at RHIC and at FRIB as well as at other international facilities, depends on the continued development of state-of-the-art hadronic transport simulations. This white paper highlights the essential role that heavy-ion collision experiments and hadronic transport simulations play in understanding strong interactions in dense nuclear matter, with an emphasis on how these efforts can be used together with microscopic approaches and neutron star studies to uncover the nuclear EOS.

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arXiv2022

Long Range Plan: Dense matter theory for heavy-ion collisions and neutron stars

Since the release of the 2015 Long Range Plan in Nuclear Physics, major events have occurred that reshaped our understanding of quantum chromodynamics (QCD) and nuclear matter at large densities, in and out of equilibrium. The US nuclear community has an opportunity to capitalize on advances in astrophysical observations and nuclear experiments and engage in an interdisciplinary effort in the theory of dense baryonic matter that connects low- and high-energy nuclear physics, astrophysics, gravitational waves physics, and data science

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arXiv2022

Using Baryonic Charge Balance Functions to Resolve Questions about the Baryo-Chemistry of the QGP

Baryon annihilations during the hadronic stage of heavy-ion collisions affects final-state baryon and antibaryon yields and final-state correlations of baryons and antibaryons. Understanding annihilation is important for addressing questions about the chemistry at the beginning of the hadronic stage, and for interpreting charge-balance correlations involving baryons. Here, charge balance functions, using protons and antiprotons binned by relative momentum, rapidity and azimuthal angle, are shown to clarify the amount of annihilation in the hadronic stage. This enables a more accurate extraction of the baryo-chemistry at the beginning of the hadronic stage. Understanding annihilation is also crucial if charge balance correlations are to be used to infer the chemistry of the earliest stages of a heavy-ion collision. Calculations are presented based on microscopic simulations of the hadronic stage coupled to a hydrodynamic description of the earlier stage, along with a detailed modeling of correlations of protons and antiprotons, known as charge-balance functions.

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arXiv2022

Confronting anomalous kaon correlations measured in Pb-Pb collisions at $\sqrt{s_{NN}} = 2.76$ TeV

Measurements of the dynamical correlations between neutral and charged kaons in central Pb-Pb collisions at $\sqrt{s_{NN}} = 2.76$ TeV by the ALICE Collaboration display anomalous behavior relative to conventional heavy-ion collision simulators such as AMPT, EPOS, and HIJING. We consider other conventional statistical models, none of which can reproduce the magnitude and centrality dependence of the correlations. The data can be reproduced by coherent emission from domains which grow in number and volume with increasing centrality. We show that the energy released by condensation of strange quarks may be sufficient to explain the anomaly.

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arXiv2022

The Interplay of Femtoscopic and Charge-Balance Correlations

Correlations driven by the constraints of local charge conservation have been shown to provide insight into the chemical evolution and diffusivity of the high-temperature matter created in ultra-relativistic heavy ion collisions. Two-particle correlations driven by final-state interactions have allowed the extraction of critical femtoscopic space-time information about the expansion and dissolution of the same collisions. Whereas correlations from final-state interactions mainly appear at small relative momenta, a few tens of MeV/$c$, charge-balance correlations extend over a range of hundreds of MeV/$c$. In nearly all previous analyses, this separation of scales is used to focus solely on one class or the other. The purpose of this study is to quantitatively understand the degree to which correlations from final-state interactions distort the interpretation of charge-balance correlations and vice versa.

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arXiv2021

The BEST framework for the search for the QCD critical point and the chiral magnetic effect

The Beam Energy Scan Theory (BEST) Collaboration was formed with the goal of providing a theoretical framework for analyzing data from the Beam Energy Scan (BES) program at the relativistic heavy ion collider (RHIC) at Brookhaven National Laboratory. The physics goal of the BES program is the search for a conjectured QCD critical point as well as for manifestations of the chiral magnetic effect. We describe progress that has been made over the previous five years. This includes studies of the equation of state and equilibrium susceptibilities, the development of suitable initial state models, progress in constructing a hydrodynamic framework that includes fluctuations and anomalous transport effects, as well as the development of freezeout prescriptions and hadronic transport models. Finally, we address the challenge of integrating these components into a complete analysis framework. This document describes the collective effort of the BEST Collaboration and its collaborators around the world.

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arXiv2021

Charge Balance Functions for Heavy-Ion Collisions at LHC Energies

Heavy-ion collisions at the LHC provide the conditions to investigate regions of quark-gluon plasma that reach higher temperatures and that persist for longer periods of time compared to collisions at the Relativistic Heavy Ion Collider. This extended duration allows correlations from charge conservation to better separate during the quark-gluon plasma phase, and thus be better distinguished from correlations that develop during the hadron phase or during hadronization. In this study charge balance functions binned by relative rapidity and azimuthal angle and indexed by species are considered. A detailed theoretical model that evolves charge correlations throughout the entirety of an event is compared to preliminary results from the ALICE Collaboration. The comparison with experiment provides insight into the evolution of the chemistry and diffusivity during the collision. A ratio of balance functions is proposed to better isolate the effects of diffusion and thus better constrain the diffusivity.

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arXiv2020

Charge Conservation and Higher Moments of Charge Fluctuations

Higher moments of distributions of net charge and baryon number in heavy-ion collisions have been proposed as signals of fundamental QCD phase transitions. In order to better understand background processes for these observables, models are presented which enable one to gauge the effects of local charge conservation, decays of resonances and clusters, Bose symmetrization, and volume fluctuations. Monte Carlo methods for generating samplings of particles consistent with local charge conservation are presented, and are followed by a review of simple analytic models involving a single type of charge with a constant experimental efficiency. The main model consists of thermal emission superimposed onto a simple parameterization of collective flow, known as a blast-wave, with emission being consistent with individual canonical ensembles. The spatial extent of local charge conservation is parameterized by the size and extent over which charge is conserved. The sensitivity of third and fourth order moments, skewness and kurtosis, to these parameters, and to beam energy and baryon density is explored. Comparisons with STAR data show that a significant part of the observed non-Poissonian fluctuations in net-proton fluctuations are explained by charge and baryon-number conservation, but that measurements of the STAR collaboration for fluctuations of net electric charge significantly differ from expectations of the models presented here.

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arXiv2019

Calculating n-Point Charge Correlations in Evolving Systems

In dynamic systems, charge susceptibilities and local charge correlations change with time. These changes are accompanied by non-local correlations which spread diffusively with time and are constrained by local charge conservation. Assuming the local features of the correlation, which for a gas would be the correlation of charges within the same particle, are equilibrated, a diagrammatic formalism is presented for calculating the evolution of the associated non-local correlations. These provide correlations of $n$ density operators at different positions for arbitrary $n$. The techniques were developed with an eye towards relativistic heavy-ion collisions, and can account for correlations indexed by up, down and strange charges. Understanding the evolution of such correlations is crucial if one is to interpret measurements of charge fluctuations from the Relativistic Heavy-Ion Collider.

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arXiv2019

Determining the Diffusivity for Light Quarks from Experiment

Charge balance functions reflect the evolution of charged pair correlations throughout the stages of pair production, dynamical diffusion, and hadronization in heavy-ion collisions. Microscopic modeling of these correlations in the full collision volume shows that the balance functions are sensitive to the diffusivity of light quarks when studied as functions of relative azimuthal angle. By restricting our analysis to K+,K- and p,pbar pairs, we find that the diffusivity of light quarks, a fundamental property not currently well understood, can be constrained by experimental measurement.

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arXiv2018

Evolving Charge Correlations in a Hybrid Model with both Hydrodynamics and Hadronic Boltzmann Descriptions

Correlations related to local charge conservation provide insight into the creation and evolution of up, down and strange charges in the quark-gluon plasma. Here, the evolution of charge correlations is overlaid onto a hydrodynamic calculation for the regions where temperature exceed 155 MeV, then transferred and carried through a microscopic model of the hadronic stage. Thus, for the first time, charge correlations are evolved consistently with a full state-of-the-art description of a heavy-ion collision. The charge correlations are projected onto charge balance functions, which characterize such correlations in the final state, and are presented as a function of relative rapidity and relative azimuthal angle for Au/Au collisions. The role of the hadronic stage is investigated. Calculation of the contribution to charge-separation observables related to the chiral magnetic effect are also presented. Calculations are compared to data from the STAR Collaboration at RHIC (Relativistic Heavy Ion Collider) data when possible.

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arXiv2018

Evolution of Charge Fluctuations and Correlations in the Hydrodynamic Stage of Heavy Ion Collisions

Charge fluctuations for a baryon-neutral quark-gluon plasma have been calculated in lattice gauge theory. These fluctuations provide a well-posed rigorous representation of the quark chemistry of the vacuum for temperatures above T_c >~ 155 MeV. Due to the finite lifetime and spatial extent of the fireball created in relativistic heavy ion collisions, charge-charge correlations can only equilibrate for small volumes due to the finite time required to transport charge. This constraint leads to charge correlations at finite relative position that evolve with time. The source and evolution of such correlations is determined by the evolution of the charge fluctuation and the diffusion constant for light quarks. Here, calculations are presented for the evolution of such correlations superimposed onto hydrodynamic simulations. Results are similar to preliminary measurements from STAR, but significant discrepancies remain.

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