Nuclear Theory·nucl-th

Friday·November 10, 2023

6 papers—1 primary·5 cross-listed

02
Theoretical Developments for Jets in Heavy-Ion Collisions
Eamonn Weitz🇫🇷
The quark-gluon plasma (QGP) is an exotic phase of matter, composed of deconfined quarks and gluons and is briefly created in heavy-ion collisions (HIC) at the LHC and at the RHIC. High-energy, self-collimated structures of final-state particles also created in HIC, called jets, probe the QGP, piercing through it on their way to the particle detector. Quantum field theory at finite temperature or thermal field theory, is then an extremely powerful tool, capable of analytically quantifying how such a high-energy object interacts with a weakly coupled thermal bath. In this thesis, we work towards the computation of corrections to two quantities, which dictate how jets are quenched by the QGP. The first being the transverse momentum broadening coefficient, which describes how the jet diffuses in transverse momentum space through its interaction with the medium. We focus on the computation of logarithmically enhanced corrections, carefully showing how the thermal scale affects the logarithmic phase space. The second is the asymptotic mass, which can be thought of as a shift in the jet dispersion relation as it undergoes forward scattering with the medium. We complete a matching calculation, which rids the mass' classical corrections of any unphysical divergences, while also beginning the completion of its full two-loop, quantum corrections.
↳ hep-phnucl-th1 citation
03
$Δ S = 0$ Hadronic Parity Violation in Next-to-Leading Order QCD: Anomalous Dimension Matrices and Their Implications
Girish Muralidhara🇺🇸 · Susan Gardner🇺🇸
We construct the effective Hamiltonian for hadronic parity violation in strangeness-nonchanging ( $Δ S = 0$ ) processes in next-to-leading order (NLO) in QCD, for all isosectors, and at a renormalization scale of 2 GeV, thus extending our earlier leading-order (LO) analysis. Hadronic parity violation, studied in the context of the low-energy interactions of nucleons and nuclei, exposes the complex interplay of weak and strong interactions in these systems, and thus supports our extension to NLO. Here we exploit the flavor-blind nature of QCD interactions to construct the needed anomalous dimension matrices from those computed in flavor physics, which we then use to refine our effective Hamiltonian and finally our predicted parity-violating meson-nucleon coupling constants, to find improved agreement with few-body experiments.
↳ hep-phnucl-thPLB(2024)·3 citations
04
The $G W$ Approximation: A Quantum Chemistry Perspective
Antoine Marie · Abdallah Ammar · Pierre-François Loos
We provide an in-depth examination of the $G W$ approximation of Green's function many-body perturbation theory by detailing both its theoretical and practical aspects in the realm of quantum chemistry. First, the quasiparticle context is introduced before delving into the derivation of Hedin's equations. From these, we explain how to derive the well-known $G W$ approximation of the self-energy. In a second time, we meticulously explain each step involved in a $G W$ calculation and what type of physical quantities can be computed. To illustrate its versatility, we consider two contrasting systems: the water molecule, a weakly correlated system, and the carbon dimer, a strongly correlated system. Each stage of the process is thoroughly detailed and explained alongside numerical results and illustrative plots. We hope that the contribution will facilitate the dissemination and democratization of Green's function-based formalisms within the computational and theoretical quantum chemistry community.
↳ physics.chem-phcond-mat.mtrl-scicond-mat.str-elmath-ph+23 citations
05
Three-body unitary coupled-channel approach to radiative $J / ψ$ decays and $η (1405/1475)$
S.X. Nakamura (Shandong Univ.)🇨🇳 · Q. Huang (Nanjing Normal Univ.)🇨🇳 · J.-J. Wu (UCAS)🇨🇳 · H.P. Peng (USTC)🇨🇳 · Y. Zhang (USTC)🇨🇳 · Y.C. Zhu (USTC)🇨🇳
Recent BESIII data on radiative $J / ψ$ decays from $\sim 1 0^{10}$ $J / ψ$ samples should significantly advance our understanding of the controversial nature of $η (1405/1475)$ . This motivates us to develop a three-body unitary coupled-channel model for radiative $J / ψ$ decays to three-meson final states of any partial wave ( $J^{P C}$ ). Basic building blocks of the model are bare resonance states such as $η (1405/1475)$ and $f_{1} (1420)$ , and $π K$ , $K K ˉ$ , and $π η$ two-body interactions that generate resonances such as $K^{*} (892)$ , $K_{0}^{*} (700)$ , and $a_{0} (980)$ . This model reasonably fits $K_{S} K_{S} π^{0}$ Dalitz plot pseudo data generated from the BESIII's $J^{P C} = 0^{-+}$ amplitude for $J / ψ \to γ K_{S} K_{S} π^{0}$ . The experimental branching ratios of $η (1405/1475) \to η π π$ and $η (1405/1475) \to γ ρ$ relative to that of $η (1405/1475) \to K K ˉ π$ are simultaneously fitted. Our $0^{-+}$ amplitude is analytically continued to find three poles, two of which correspond to $η (1405)$ on different Riemann sheets of the $K^{*} K ˉ$ channel, and the third one for $η (1475)$ . This is the first pole determination of $η (1405/1475)$ and, furthermore, the first-ever pole determination from analyzing experimental Dalitz plot distributions with a manifestly three-body unitary coupled-channel framework. Process-dependent $η π π$ , $γ π^{+} π^{-}$ , and $π π π$ lineshapes of $J / ψ \to γ (0^{-+}) \to γ (η π π)$ , $γ (γ ρ)$ , and $γ (π π π)$ are predicted, and are in reasonable agreement with data. A triangle singularity is shown to play a crucial role to cause the large isospin violation of $J / ψ \to γ (π π π)$ .
↳ hep-phhep-exnucl-thPRD(2024)·14 citations
06
Particle and pair spectra for strongly correlated Fermi gases: A real-frequency solver
Tilman Enss
The strongly attractive Fermi gas in the BCS-BEC crossover is efficiently described in terms of coupled fermions and fermion pairs, or molecules. We compute the spectral functions of both fermions and pairs in the normal state near the superfluid transition using a Keldysh formulation in real frequency. The mutual influence between fermions and pairs is captured by solving the self-consistent Luttinger-Ward equations: these include both the damping of fermions by scattering off dressed pairs, as well as the decay of pair states by dissociation into two dressed fermions. The pair spectra encode contact correlations between fermions and form the basis for computing dynamical response functions and transport properties.
↳ cond-mat.quant-gascond-mat.str-elnucl-thPRA(2024)·5 citations

Affiliations

first authorsco-authorsvia INSPIRE

Theoretical Developments for Jets in Heavy-Ion Collisions

ΔS=0 Hadronic Parity Violation in Next-to-Leading Order QCD: Anomalous Dimension Matrices and Their Implications

The GW Approximation: A Quantum Chemistry Perspective

Three-body unitary coupled-channel approach to radiative J/ψ decays and η(1405/1475)

Particle and pair spectra for strongly correlated Fermi gases: A real-frequency solver

Affiliations

$Δ S = 0$ Hadronic Parity Violation in Next-to-Leading Order QCD: Anomalous Dimension Matrices and Their Implications

The $G W$ Approximation: A Quantum Chemistry Perspective

Three-body unitary coupled-channel approach to radiative $J / ψ$ decays and $η (1405/1475)$