Nuclear Theory·nucl-th

Monday·January 13, 2020

8 papers—3 primary·5 cross-listed

01
[Submitted on 10 Jan 2020]
New Ideas in Constraining Nuclear Forces
I. Tews🇺🇸 · Z. Davoudi🇺🇸 · A. Ekström🇸🇪 · J.D. Holt🇨🇦 · J.E. Lynn🇩🇪
In recent years, nuclear physics has benefited greatly from the development of powerful ab initio many-body methods and their combination with interactions from chiral effective field theory. With increasing computational power and continuous development of these methods, we are entering an era of precision nuclear physics. Indeed, uncertainties from nuclear Hamiltonians now dominate over uncertainties from many-body methods. This review summarizes the current status of, and future directions in, deriving and constraining nuclear Hamiltonians.
Comments:
44 pages, 16 figures, Topical Review of ECT* workshop "New Ideas in Constraining Nuclear Forces", published version
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2001.03334 [pdf]
J.Phys.G(2020)·60 citations
02
[Submitted on 10 Jan 2020]
A Non-Equilibrium Approach to Photon Emission from the Late Stages of Relativistic Heavy-Ion Collisions
Anna Schäfer🇩🇪 · Juan M. Torres-Rincon🇩🇪 · Charles Gale🇨🇦 · Hannah Elfner🇩🇪
Cross sections for photon production in hadronic scattering processes have been calculated according to an effective chiral field theory. For $π + ρ \to π + γ$ and $π + π \to ρ + γ$ processes, these cross sections have been implemented into a novel hadronic transport approach (SMASH), which is suitable for collisions at low and intermediate energies. The implementation is verified by systematically comparing the thermal photon rate to theoretical expectations. The photon rates we obtain are compared to previous works, where scattering processes mediated by $ω$ mesons are found to contribute significantly to the total photon production. Finally, the impact of considering the finite width of the $ρ$ meson is investigated, and a significant enhancement of photon production in the low-energy region is observed. This work is the first step towards a consistent treatment of photon emission in hybrid hydrodynamics+transport approaches. The quantification of the importance of the hadronic stage for the resolution of the direct photon flow puzzle is a next step and can be applied to identify equilibrium and non-equilibrium effects in the hadronic afterburner.
Comments:
4 pages, 3 figures, proceedings of Quark Matter 2019
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
2001.03378 [pdf]
NPA(2021)·5 citations
03
[Submitted on 10 Jan 2020]
Supercritically charged objects and electron-positron pair creation
Cheng-Jun Xia🇨🇳 · She-Sheng Xue🇮🇹 · Ren-Xin Xu🇨🇳 · Shan-Gui Zhou🇨🇳
We investigate the stability and $e^{+} e^{-}$ pair creation of supercritically charged superheavy nuclei, $u d$ QM nuggets, strangelets, and strangeon nuggets based on Thomas-Fermi approximation. The model parameters are fixed by reproducing their masses and charge properties reported in earlier publications. It is found that $u d$ QM nuggets, strangelets, and strangeon nuggets may be more stable than $^{56}$ Fe at $A ≳ 315$ , $5 \times 1 0^{4}$ , and $1.2 \times 1 0^{8}$ , respectively. For those stable against neutron emission, the most massive superheavy element has a baryon number $\sim$ 965, while $u d$ QM nuggets, strangelets, and strangeon nuggets need to have baryon numbers larger than $39$ , 433, and $2.7 \times 1 0^{5}$ . The $e^{+} e^{-}$ pair creation will inevitably start for superheavy nuclei with charge numbers $Z \geq 177$ , $u d$ QM nuggets with $Z \geq 163$ , strangelets with $Z \geq 192$ , and strangeon nuggets with $Z \geq 212$ . A universal relation $Q / R_{e} = (m_{e} - μ ˉ_{e}) / α$ is obtained at a given electron chemical potential $μ ˉ_{e}$ , where $Q$ is the total charge and $R_{e}$ the radius of electron cloud. This predicts the maximum charge number by taking $μ ˉ_{e} = - m_{e}$ . For supercritically charged objects with $μ ˉ_{e} < - m_{e}$ , the decay rate for $e^{+} e^{-}$ pair production is estimated based on the JWKB approximation. It is found that most positrons are emitted at $t ≲ 1 0^{- 15}$ s, while a long lasting positron emission is observed for large objects with $R ≳ 1000$ fm. The emission and annihilation of positrons from supercritically charged objects may be partially responsible for the short $γ$ -ray burst during the merger of binary compact stars, the 511 keV continuum emission, as well as the narrow faint emission lines in X-ray spectra from galaxies and galaxy clusters.
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2001.03531 [pdf]
PRD(2020)·19 citations

Affiliations

first authorsco-authorsvia INSPIRE

New Ideas in Constraining Nuclear Forces

A Non-Equilibrium Approach to Photon Emission from the Late Stages of Relativistic Heavy-Ion Collisions

Supercritically charged objects and electron-positron pair creation

Affiliations