Nuclear Theory·nucl-th

Tuesday·March 29, 2022

16 papers—9 primary·7 cross-listed

10
[Submitted on 25 Mar 2022] (cross-list from hep-lat)
The pion-nucleon sigma term from Lattice QCD
Rajan Gupta🇺🇸 · Tanmoy Bhattacharya🇺🇸 · Martin Hoferichter🇨🇭 · Emanuele Mereghetti🇺🇸 · Sungwoo Park🇺🇸 · Boram Yoon🇺🇸
We summarize recent evidence, both from lattice QCD and chiral perturbation theory, that suggests that larger-than-expected excited-state contamination could be the reason for the tension between phenomenological determinations and previous direct lattice-QCD calculations of the pion--nucleon sigma term $σ_{π N}$ . In addition, we extend the $χ$ PT analysis by calculating the corrections due to including the $Δ (1232)$ resonance as an explicit degree of freedom. This correction is found to be small, thereby corroborating the excited-state effects found in the $Δ$ -less calculation and the result for $σ_{π N}$ .
Comments:
Includes new analysis of $Δ$ corrections to excited-state contamination. Contribution to the 10th International Workshop on Chiral Dynamics
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2203.13862 [pdf]
PoS(2024)·11 citations
11
[Submitted on 25 Mar 2022] (cross-list from hep-ph)
Numerical calculation of 3-pion Coulomb scattering using scalar QED
Dhevan Gangadharan🇺🇸
The Coulomb scattering between three charged pions is shown to be perturbatively calculable using scalar QED for the relative momenta accessible to high-energy experiments of particle collisions. For the triplet relative momenta, $Q_{3} ≳ 50$ MeV/ $c$ , the calculated three-pion correlation function at $O (α^{2})$ is very similar to the commonly-used triple-product of pair factors -- Riverside approximation. At lower $Q_{3}$ , but above the lowest existing experimental measurement of $\sim 15$ MeV/ $c$ , terms of $O (α^{3})$ or higher are needed to obtain a convincing description of three-pion Coulomb interactions. This is in contrast to two-pion correlations, for which the known exact solution is shown to be saturated by the lower orders at comparable pair relative momenta.
Comments:
6 pages, 7 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2203.13881 [pdf]
PLB(2022)·0 citations
12
[Submitted on 26 Mar 2022] (cross-list from hep-ph)
Constraining non-dissipative transport coefficients in global equilibrium
Shi-Zheng Yang🇨🇳 · Jian-Hua Gao🇨🇳 · Zuo-Tang Liang🇨🇳
The fluid in global equilibrium must fulfill some constraints. These constraints can be derived from quantum statistical theory or kinetic theory. In this paper we will show that how these constraints can be applied to determine the non-dissipative transport coefficients for chiral systems along with the energy-momentum conservation, chiral anomaly for charge current and trace anomaly in energy-momentum tensor.
Comments:
9 pages, no figures, submitted to Symmetry for the special issue "Symmetry with Chiral Magnetic Effects and Chiral Transports"
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
2203.14023 [pdf]
Symmetry(2022)·9 citations
13
[Submitted on 28 Mar 2022] (cross-list from physics.ins-det)
Simulating Araponga -- The High-Resolution Diffractometer of Brazilian Multipurpose Reactor
Alexandre P.S. Souza · Luiz P. de Oliveira · Frederico A. Genezini · Adimir dos Santos
The Brazilian Multipurpose Reactor (RMB) is a fundamental project that aims to turn Brazil into a self-sufficient country in the production of radioisotopes and radiopharmaceuticals to supply the Unified Health System (SUS) as much as the private institutions. In addition, the RMB project describes other applications as irradiation and testing of nuclear fuels and structural material analysis, for instance. There are many techniques in the project to study structural aspects of materials, where neutron diffraction represents one of the priorities for implementation. This technique will take place mainly on two diffractometers on Thermal Neutron Guide 1 (TG1), namely Araponga, a high-resolution diffractometer, and Flautim, a high-intensity diffractometer. In this work, we study the performance of the Araponga diffractometer through McStas simulations with input produced by the MCNP code of the RMB core. We investigate the neutron flux values considering a state-of-art high-resolution diffractometer, and the results are promising since some simulated scenarios present values compatible with high-intensity devices.
Comments:
10 pages, 2 figures
Subjects:
Instrumentation and Detectors (physics.ins-det); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2203.14423 [pdf]
Brazilian Journal of Radiation Sciences, …·2 citations
14
[Submitted on 28 Mar 2022] (cross-list from hep-th)
Chiral sum rule on the light front and the 3D image of the pion
Yang Li🇨🇳 · Pieter Maris🇺🇸 · James P. Vary🇺🇸
The lightest meson, the pion, features two faces -- one is the elementary Goldstone boson of QCD and the other is the structured bound state of quarks and gluons. To accommodate both in a single light-front wave function in the valence space, we obtain a sum rule by analyzing the conserved axial-vector current and the general structures of the wave functions. Using an analytic model motivated by holography, we show this sum rule is consistent with requirements of chiral symmetry breaking in AdS/QCD. Within this model, we find a remarkable feature of the pion, namely that the density is mostly uniform inside its radius; furthermore, we obtain good agreement with the experimental pion form factor at spacelike momenta.
Comments:
9 pages, 3 figures. Added the pion electromagnetic form factor results to matched the published version
Subjects:
High Energy Physics — Theory (hep-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2203.14447 [pdf]
PLB(2023)·12 citations
15
[Submitted on 28 Mar 2022] (cross-list from hep-ph)
Two-Photon-Exchange effect in $e p \to e n π^{+}$ at small $- t$ with the hadronic model and dispersion relation approach
Qian-Qian Guo🇨🇳 · Hai-Qing Zhou🇨🇳
In this work, the two-photon-exchange (TPE) effect in $e p \to e n π^{+}$ at small $- t$ is discussed. In the previous work, the TPE contribution with one $π$ intermediate state is estimated numerically within a hadronic model under the pion-dominance approximation. Here we extend the discussion to include one $ρ$ intermediate state. The TPE contribution can be described by one scalar function in the limit $m_{e} \to 0$ , the dispersion relation (DR) satisfied by this scalar function is analysed. The analytic expressions for the imaginary parts of the TPE contributions from one $π$ or one $ρ$ intermediate state are given within the hadronic model. Combining these analytic expressions and the DR, the corresponding real parts of the TPE contributions can be estimated easily at any available region. This can help the further experimental analysis to include the TPE contributions in a convenient way. The numeric results show that the TPE correction with one $ρ$ intermediate state is much smaller than that with one $π$ intermediate state in the current energy region. These results suggest that the TPE contribution with an elastic state is the main TPE contribution in $e p \to e n π^{+}$ at small $- t$ .
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2203.14570 [pdf]
PRC(2022)·6 citations
16
[Submitted on 25 Mar 2022] (cross-list from astro-ph.HE)
Partially accreted crusts of neutron stars
Lami Suleiman🇵🇱 · Julian-Leszek Zdunik🇵🇱 · Pawel Haensel🇵🇱 · Morgane Fortin🇵🇱
Neutron stars in low-mass binary systems are subject to accretion. The common assumption in studying the properties of the neutron star crust is the fully accreted crust approximation. However, observations of some X-ray transient sources indicate that the original crust has not been completely replaced by accreted material, but is partly composed of the compressed original crust. A two-part (or hybrid) crust made of the original crust that is compressed and of the accreted material crashing onto it was reconstructed as a function of the accretion stage. The differences in the composition and energy sources for the fully accreted and hybrid crusts influence the cooling and transport properties. A simple semi-empirical formula of a compressible liquid drop was used. We compared the nuclear reactions triggered by compression in the original crust and in the accreted matter part of the hybrid crust. We discuss another crust compression astrophysical phenomenon related to spinning neutron stars. The compression of the originally catalyzed outer crust triggers exothermic reactions (electron captures and pycnonuclear fusions) that deposit heat in the crust. The heat sources are cataloged as a function of the compression until the fully accreted crust approximation is reached. The pressure at which neutron drip occurs is a nonmonotonic function of the depth, leading to a temporary neutron drip anomaly. The additional potential source of energy for partially accreted crusts is the occurrence of a density inversion phenomenon between some compressed layers. The original crust of a neutron star cannot be neglected when the original crust is not fully replaced by the accreted matter. The amount of heat associated with the compression of the original crust is on the same order of magnitude as that from the sources acting in the accreted part of the hybrid crust.
Comments:
17 pages, 10 figures, 4 files in Ancillary (2 movies, 2 .res files)
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
arXiv:
2203.14735 [pdf]
Astron.Astrophys.(2022)·8 citations

Affiliations

first authorsco-authorsvia INSPIRE

The pion-nucleon sigma term from Lattice QCD

Numerical calculation of 3-pion Coulomb scattering using scalar QED

Constraining non-dissipative transport coefficients in global equilibrium

Simulating Araponga -- The High-Resolution Diffractometer of Brazilian Multipurpose Reactor

Chiral sum rule on the light front and the 3D image of the pion

Two-Photon-Exchange effect in ep→enπ+ at small −t with the hadronic model and dispersion relation approach

Partially accreted crusts of neutron stars

Affiliations

Two-Photon-Exchange effect in $e p \to e n π^{+}$ at small $- t$ with the hadronic model and dispersion relation approach