Nuclear Theory·nucl-th

Tuesday·August 22, 2023

15 papers—7 primary·8 cross-listed

08
Pre-equilibrium photons from the early stages of heavy-ion collisions
Oscar Garcia-Montero🇩🇪 · Aleksas Mazeliauskas🇩🇪 · Philip Plaschke🇩🇪 · Sören Schlichting🇩🇪
We use QCD kinetic theory to compute photon production in the chemically equilibrating Quark-Gluon Plasma created in the early stages of high-energy heavy-ion collisions. We do a detailed comparison of pre-equilibrium photon rates to the thermal photon production. We show that the photon spectrum radiated from a hydrodynamic attractor evolution satisfies a simple scaling form in terms of the specific shear viscosity $η / s$ and entropy density $d S / d ζ \sim (T τ^{1/3})^{3/2}_{\infty}$ . We confirm the analytical predictions with numerical kinetic theory simulations. We use the extracted scaling function to compute the pre-equilibrium photon contribution in $s_{N N} = 2.76 TeV$ 0-20\% PbPb collisions. We demonstrate that our matching procedure allows for a smooth switching from pre-equilibrium kinetic to thermal hydrodynamic photon production. Finally, our publicly available implementation can be straightforwardly added to existing heavy ion models.
↳ hep-phnucl-thJHEP(2024)·37 citations
09
Recent developments in mathematical aspects of relativistic fluids
Marcelo M. Disconzi
We review some recent developments in mathematical aspects of relativistic fluids. The goal is to provide a quick entry point to some research topics of current interest that is accessible to graduate students and researchers from adjacent fields, as well as to researches working on broader aspects of relativistic fluid dynamics interested in its mathematical formalism. Instead of complete proofs, which can be found in the published literature, here we focus on the proofs' main ideas and key concepts. After an introduction to the relativistic Euler equations, we cover the following topics: a new wave-transport formulation of the relativistic Euler equations tailored to applications; the problem of shock formation for relativistic Euler; rough (i.e., low-regularity) solutions to the relativistic Euler equations; the relativistic Euler equations with a physical vacuum boundary; relativistic fluids with viscosity. We finish with a discussion of open problems and future directions of research.
↳ math.APgr-qcmath-phmath.MP+2Living Rev.Rel.(2024)·29 citations
10
Strongly hyperbolic quasilinear systems revisited, with applications to relativistic fluid dynamics
Marcelo M. Disconzi · Yuanzhen Shao
We revisit the theory of first-order quasilinear systems with diagonalizable principal part and only real eigenvalues, what is commonly referred to as strongly hyperbolic systems. We provide a self-contained and simple proof of local well-posedness, in the Hadamard sense, of the Cauchy problem. Our regularity assumptions are very minimal. As an application, we apply our results to systems of ideal and viscous relativistic fluids, where the theory of strongly hyperbolic equations has been systematically used to study several systems of physical interest.
↳ math.APgr-qcmath-phmath.MP+1Asymptotic Anal.(2024)·8 citations
11
Overview: Jet quenching with machine learning
Yi-Lun Du🇨🇳
Jets are suppressed and modified in heavy ion collisions, which serve as powerful probes to the properties of the quark-gluon plasma (QGP). Attributed to the abundant information carried by the jet constituents and reconstructed substructures, plenty of interesting applications of machine learning techniques have been made on a jet-by-jet basis to study the jet quenching phenomena. Here we review recent proceedings on this topic including the tasks of reconstructing jet momentum in heavy ion collisions, classifying quenched jets and unquenched jets, identifying jet energy loss, locating the jet creation points as well as distinguishing between quark- and gluon-initiated jets in the QGP. Such jet-by-jet analyses will allow us to have a better handle on the jet reconstruction and selections to investigate the effects of jet modifications and push forward the long-standing goal of jet tomographic probes of the QGP.
↳ hep-phhep-exnucl-th6 citations
12
Nature of $X (3872)$ from its radiative decay
Shuo-Ying Yu🇨🇳 · Xian-Wei Kang🇨🇳
We study the radiative decay of $X (3872)$ based on the assumption that $X (3872)$ is regarded as a $c c$ charmonium with quantum number $J^{P C} = 1^{++}$ ( $J, P, C$ represent the spin, parity and charge conjugation, respectively). The form factors of $X (3872)$ transitions to $J / ψ γ$ and $ψ^{'} γ$ ( $ψ^{'}$ denotes $ψ (2 S)$ throughout the paper) are calculated in the framework of the covariant light-front quark model. The phenomenological wave function of a meson depends on the parameter $β$ , whose inverse essentially describes the confinement scale. In the present work, the parameters $β$ for the vector $J / ψ$ and $ψ^{'}$ mesons will be determined through their decay constants, which are obtained from the experimental values of their partial decay widths to the electron-positron pair. For $X (3872)$ , we determined the value of $β$ by the decay width of $X (3872) \to ψ^{'} γ$ . Then, we examined the width of $X (3872) \to J / ψ γ$ in a manner of parameter-free prediction and compared it with the experimental value. As a result, an inconsistency or contradiction occurs between the widths of $X (3872) \to J / ψ γ$ and $X (3872) \to ψ^{'} γ$ . We thus conclude that $X (3872)$ cannot be a pure $c c$ resonance and that other components are necessary in its wave function.
↳ hep-phhep-exnucl-thPLB(2024)·16 citations
13
Electromagnetic radiation at extreme angular velocity
Matteo Buzzegoli🇺🇸 · Kirill Tuchin🇺🇸
We consider a system rotating at extremely high angular velocity, so that its matter is found mostly at the light-cylinder. We posit that it can be described by quantum fields confined to the two-dimensional cylindrical surface rotating about its symmetry axis. We apply this model to study the electromagnetic radiation. In particular, we compute the photon spectrum emitted by the quark-gluon plasma.
↳ hep-phgr-qchep-thnucl-thJHEP(2023)·12 citations
14
Modeling Backward-Angle ( $u$ -channel) Virtual Compton Scattering at an Electron-Ion Collider
Zachary Sweger🇺🇸 · Spencer R. Klein🇺🇸 · Yuanjing Ji🇺🇸 · Minjung Kim🇺🇸 · Saeahram Yoo🇺🇸 · Ziyuan Zeng🇺🇸 · Daniel Cebra🇺🇸 · Xin Dong🇺🇸
High-energy backward ( $u$ -channel) reactions can involve very large momentum transfers to the target baryons, shifting them by many units of rapidity. These reactions are difficult to understand in conventional models in which baryon number is carried by the valence quarks. Backward Compton scattering is an especially attractive experimental target, because of its simple final state. There is currently limited data on this process, and that data is at low center-of-mass energies. In this paper, we examine the prospects for studying backward Compton scattering at the future Electron-Ion Collider (EIC). We model the cross-section and kinematics using the limited data on backward Compton scattering and backward meson production, and then simulate Compton scattering at EIC energies, in a simple model of the ePIC detector. Generally, the proton is scattered toward mid-rapidity, while the produced photon is in the far-forward region, visible in a Zero Degree Calorimeter (ZDC). We show that the background from backward $π^{0}$ production can be rejected using a high-resolution, well-segmented ZDC.
↳ hep-phnucl-exnucl-thPRC(2023)·6 citations
15
Diffractive Processes at Next-to-Leading Order in the Dipole Picture
Jani Penttala🇫🇮
In this thesis, we calculate diffractive processes at next-to-leading order (NLO) in the high-energy limit, with an emphasis on exclusive vector meson production and inclusive diffraction in deep inelastic scattering (DIS). Calculations in the high-energy limit can be done using the dipole picture, the basics of which are briefly reviewed. This includes using the color-glass condensate effective field theory to describe the nonperturbative dipole-target scattering amplitude which appears in practically all calculations in the dipole picture. The universality of the dipole-target scattering amplitude at NLO is shown numerically, in the sense that the same dipole-target scattering amplitude can be used to describe the data in both massless and massive quark production in inclusive DIS, and also in diffractive processes where exclusive vector meson production is considered. The analytical NLO calculations of exclusive vector meson production and inclusive diffraction in DIS are also explained. Exclusive vector meson production is calculated in the nonrelativistic limit for heavy mesons and the limit of large photon virtuality for light mesons. Also, the importance of including relativistic corrections to the heavy vector meson wave function in exclusive vector meson production is considered. For inclusive diffraction in DIS, we focus on the NLO corrections to the final state and show how the divergences cancel.
↳ hep-phnucl-thJYU Dissertations 668, 2023, ISBN:978-951…·3 citations

Affiliations

first authorsco-authorsvia INSPIRE