Nuclear Theory·nucl-th

Monday·March 11, 2024

5 papers—3 primary·2 cross-listed

01
Electrical conductivity and shear viscosity of a pion gas in a thermo-magnetic medium
Pallavi Kalikotay🇧🇩 · Snigdha Ghosh🇮🇳 · Nilanjan Chaudhuri🇮🇳 · Pradip Roy🇮🇳 · Sourav Sarkar🇮🇳
We evaluate the electrical conductivity and shear viscosity of a interacting pion gas in a thermo-magnetic medium using the kinetic theory. The collision term of the relativistic Boltzmann transport equation in presence of background magnetic field is solved using the relaxation time approximation. The medium modified relaxation time is obtained from the corresponding in-medium $π π \to π π$ scattering cross-section calculated using the thermo-magnetic $ρ$ propagator. It is observed that the average relaxation time shows a $1/ T^{4}$ variation with temperature for a fixed value of magnetic field. The relaxation time shows a mild oscillatory variation with respect to the magnetic field. It is also observed that the medium dependent scattering cross-section causes a considerable amount of influence on the electrical conductivity and shear viscosity compared to its vacuum counterpart.
nucl-thhep-phEPJA(2024)·4 citations
02
Shape of 12C
Masaaki Kimura · Yasutaka Taniguchi
We have examined the hypothesis by Bijker and Iachello who asserted that 12C has an internal structure with three alpha particles arranged in a triangular shape, leading to the formation of the ground rotational band consisting of 0+, 2+, 3-, 4 $^{\pm}$ and 5- states. Following this idea, we reconstructed the intrinsic shape of 12C using experimental electron scattering data with minimal theoretical assumption. Our sole assumption was that the observed 0+, 2+, 3-, and 4+ states share a common internal structure, forming a rotational spectrum. The reconstructed intrinsic density showed a beautiful triangular shape with three peaks implying alpha cluster formation in the ground band.
nucl-thnucl-exEPJA(2024)·4 citations
03
Confronting the Lippmann-Schwinger equation and the $N / D$ method for coupled-wave separable potentials
M.S. Sánchez🇪🇸 · J.A. Oller🇪🇸 · D.R. Entem🇪🇸
We study a family of separable potentials with and without added contact interactions by solving the associated Lippmann-Schwinger equation with two coupled partial waves. The matching of the resulting amplitude matrix with the effective-range expansion is studied in detail. When a counterterm is included in the potential we also carefully discuss its renormalization. Next, we use the matrix $N / D$ method and study whether the amplitude matrices from the potentials considered admit an $N / D$ representation in matrix form. As a novel result we show that it is typically not possible to find such matrix representation for the coupled partial-wave case. However, a separate $N / D$ representation for each coupled partial wave, a valid option known in the literature, is explicitly implemented and numerically solved in cases where the matrix $N / D$ method is unavailable.
nucl-thhep-phAnnals Phys.(2024)·1 citation
04
Scaling of pre-equilibrium dilepton production in QCD Kinetic Theory
Oscar Garcia-Montero🇩🇪 · Philip Plaschke🇩🇪 · Sören Schlichting🇩🇪
We use QCD kinetic theory to compute dilepton production coming from the pre-equilibrium phase of the Quark-Gluon Plasma created in high-energy heavy-ion collisions. We demonstrate that the dilepton spectrum exhibits a simple scaling in terms of the specific shear viscosity $η / s$ and entropy density $d S / d ζ \sim (T τ^{1/3})_{\infty}^{3/2}$ , which can be derived from dimensional analysis in the presence of a pre-equilibrium attractor. Based on this scaling we perform event-by-event calculations of in-medium dilepton production and determine the invariant mass range where the pre-equilibrium yield is the leading contribution.
↳ hep-phnucl-thPRD(2025)·23 citations
05
Phenomenological model for $γ γ^{*} \to K K ˉ^{*} (892)$ constraining the $f_{1} (1420)$ transition form factor
Xiu-Lei Ren🇩🇪 · Igor Danilkin🇩🇪 · Marc Vanderhaeghen🇩🇪
We present a phenomenological study of the $γ γ^{*} \to K K ˉ^{*} (892)$ process by including the $s$ -channel production of the $η (1475)$ and $f_{1} (1420)$ resonances. The non-resonant channel via $K$ - and $K^{*}$ -exchanges is investigated carefully by performing the Lorentz tensor decomposition and is constructed to yield a correct high-energy Regge behavior. The transition form factor of $f_{1} (1420)$ is adjusted to achieve a reasonable description of the existing L3 data in the $f_{1} (1420)$ resonance region. This model is intended to serve as a Monte Carlo generator for the analysis currently being performed by the BESIII Collaboration. We also estimate the polarized $γ γ^{*} \to K K ˉ^{*} (892)$ cross sections and demonstrate how to extract the transition form factors of $f_{1} (1420)$ from the polarized cross sections.
↳ hep-phnucl-thPRD(2024)·1 citation

Affiliations

first authorsco-authorsvia INSPIRE

Electrical conductivity and shear viscosity of a pion gas in a thermo-magnetic medium

Shape of 12C

Confronting the Lippmann-Schwinger equation and the N/D method for coupled-wave separable potentials

Scaling of pre-equilibrium dilepton production in QCD Kinetic Theory

Phenomenological model for γγ∗→KKˉ∗(892) constraining the f1​(1420) transition form factor

Affiliations

Confronting the Lippmann-Schwinger equation and the $N / D$ method for coupled-wave separable potentials

Phenomenological model for $γ γ^{} \to K K ˉ^{} (892)$ constraining the $f_{1} (1420)$ transition form factor