Nuclear Theory·nucl-th

Monday·May 2, 2022

7 papers—3 primary·4 cross-listed

01
[Submitted on 29 Apr 2022]
Nuclear equation of state for arbitrary proton fraction and temperature based on chiral effective field theory and a Gaussian process emulator
J. Keller🇩🇪 · K. Hebeler🇩🇪 · A. Schwenk🇩🇪
We calculate the equation of state of asymmetric nuclear matter at finite temperature based on chiral effective field theory interactions to next-to-next-to-next-to-leading order. Our results assess the theoretical uncertainties from the many-body calculation and the chiral expansion. Using a Gaussian process emulator for the free energy, we derive the thermodynamic properties of matter through consistent derivatives and use the Gaussian process to access arbitrary proton fraction and temperature. This enables a first nonparametric calculation of the equation of state in beta equilibrium, and of the speed of sound and the symmetry energy at finite temperature. Moreover, our results show that the thermal part of the pressure decreases with increasing densities.
Comments:
7 pages, 5 figures, minor updates and improvements, published version
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Experiment (nucl-ex)
arXiv:
2204.14016 [pdf]
PRL(2023)·117 citations
02
[Submitted on 29 Apr 2022]
Perturbative QCD and the Neutron Star Equation of State
Rahul Somasundaram🇫🇷 · Ingo Tews🇺🇸 · Jérôme Margueron🇫🇷
We construct a physics-agnostic approach to the neutron star (NS) equation of state (EoS) based on a sound speed model, which connects both low-density information from nuclear theory and high-density constraints from perturbative QCD (pQCD). Using this approach, we study the impact of pQCD calculations on NS EoS that have been constrained by astrophysical observations. We find that pQCD affects the EoS mainly beyond the densities realized in NS. Furthermore, we observe an interesting interplay between pQCD and astrophysical constraints, with pQCD preferring softer EoS for the heaviest NS while recent NICER observations suggest the EoS to be stiffer. We explore the sensitivity of our findings to pQCD uncertainties and study the constraining power of pQCD if future observations of heavy NS were to suggest radii larger than 13 km.
Comments:
7 pages, 6 figures. Comments welcome
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2204.14039 [pdf]
PRC(2023)·81 citations
03
[Submitted on 29 Apr 2022]
Predictions of conventional and microscopic triaxial cranking models for light nuclei
Parviz Gulshani
The conventional cranking model for uniaxial rotation is frequently used to study rotational features in deformed nuclei. However, the model uses a constant angular velocity. To investigate the effect of a dynamic angular velocity, a quantal microscopic time-reversal and D2 invariant cranking model for triaxial rotation (MSCRM3) including residual correction terms is derived from a unitary transformation of the nuclear Schrodinger equation and using Hartree-Fock approach. Except for the angular velocity and residual terms, MSCRM3 and the conventional cranking model for triaxial rotation (CCRM3) Schrodinger equations are identical in form, and are solved iteratively in a similar manner. The article identifies the differences in the rotational features predicted by CCRM3 and MSCRM3 for 20Ne, 24Mg, and 28Si using a self-consistent deformed harmonic-oscillator potential. The rotational features studied are: rotational relaxation of the intrinsic system, stability of the rotational states, various rotation modes, nuclear shapes, their transitions, and band termination. MSCRM3 predicts the observed reduced energy-level spacing in 20Ne between J=6 and 8 and attributes its occurrence to quenching of a wobbly rotation. The remaining discrepancy between the observed and MSCRM3-predicted excitation energies for 20Ne is removed by including the spin-orbit interaction and the residuals of the square of the angular momentum and interaction. CCRM3 does not predict the three dimensional phenomena predicted by MSCRM3 (such as the reduced energy-level spacing in 20Ne and the rotational-band termination at J=12 in prolate 28Si and triaxial 24Mg, etc. arising from the angular velocity). We, therefore, conclude that CCRM3 is effectively a uniaxial rotation model. Therefore, using CCRM3 or its uniaxial version, one would miss capturing three-dimensional rotation phenomena.
Comments:
10 pages, 4 figures. The abstract, model derivation, and summary-conclusion section have been revised to clarify the results and conclusions drawn and make them more concise
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2204.14207 [pdf]
1 citation
04
[Submitted on 29 Apr 2022] (cross-list from hep-ph)
Nucleon and $Δ$ resonances in $γ n \to K^{+} Σ^{-}$ photoproduction
Neng-Chang Wei🇨🇳 · Ai-Chao Wang🇨🇳 · Fei Huang🇨🇳 · Kanzo Nakayama🇺🇸
The most recent data on beam asymmetries, $Σ$ , and beam-target asymmetries, $E$ , from the CLAS Collaboration, together with the previous data on differential cross sections and beam asymmetries from the CLAS and LEPS Collaborations, for the $γ n \to K^{+} Σ^{-}$ reaction are studied based on an effective Lagrangian approach in the tree-level Born approximation. The $t$ -channel $K$ and $K^{*} (892)$ exchanges, the $u$ -channel $Σ$ exchange, the interaction current, and the exchanges of $N$ , $Δ$ , and their excited states in the $s$ channel are considered in constructing the reaction amplitudes to describe the available experimental data. The reaction mechanisms of $γ n \to K^{+} Σ^{-}$ are analyzed, and the associated resonances' parameters are extracted. The numerical results show that the $Δ$ exchange and the $N (1710) 1/ 2^{+}$ , $N (1880) 1/ 2^{+}$ , $N (1900) 3/ 2^{+}$ , and $Δ (1920) 3/ 2^{+}$ resonance exchanges in the $s$ -channel dominate the $γ n \to K^{+} Σ^{-}$ reaction in the lower energy region, and the $t$ -channel $K^{*} (892)$ exchange plays a crucial role at forward angles in the higher energy region.
Comments:
To be published in Physical Review D; 11 pages, 5 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2204.13922 [pdf]
PRD(2022)·14 citations
05
[Submitted on 29 Apr 2022] (cross-list from hep-ph)
Complete calculation of exclusive heavy vector meson production at next-to-leading order in the dipole picture
Heikki Mäntysaari🇫🇮 · Jani Penttala🇫🇮
Exclusive production of transversely polarized heavy vector mesons in deep inelastic scattering at high energy is calculated at next-to-leading order accuracy in the Color Glass Condensate framework. In addition to the first QCD correction proportional to the strong coupling constant $α_{s}$ , we systematically also include the first relativistic correction proportional to the heavy quark velocity squared $v^{2}$ . When combined with our previously published results for longitudinal vector meson production at next-to-leading order accuracy, these results make phenomenological calculations of heavy vector meson production possible at the order $O (α_{s} v^{0}, α_{s}^{0} v^{2})$ . When applied to $J / ψ$ and $Υ$ production at HERA and at the LHC, a good agreement between the next-to-leading order calculations and experimental data is found. Additionally, we demonstrate that vector meson production can provide additional constraints compared to structure function analyses when the nonperturbative initial condition for the Balitsky-Kovchegov evolution equation is extracted.
Comments:
44 pages, 17 figures; v2: Corrected typos, matches published version
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2204.14031 [pdf]
JHEP(2022)·84 citations
06
[Submitted on 29 Apr 2022] (cross-list from hep-ph)
Dynamic Magnetic Response of Quark-Gluon Plasma to Electromagnetic Fields
Christopher Grayson🇺🇸 · Martin Formanek🇺🇸 · Johann Rafelski🇺🇸 · Berndt Mueller🇺🇸
We investigate the electromagnetic response of a viscous quark-gluon plasma in the framework of the relativistic Boltzmann equation with current conserving collision term. Our formalism incorporates dissipative effects at all orders in linear response to the electromagnetic field while accounting for the full space- and time-dependence of the perturbing fields. As an example, we consider the collision of two nuclei in a stationary, homogeneous quark-gluon plasma. We show that for large collision energies the induced magnetic fields are governed by the response of quark-gluon plasma along the light-cone. In this limit we derive an analytic expression for the magnetic field along the beam axis between the receding nuclei and show that its strength varies only weakly with collision energy for $s_{NN} \geq 30$ GeV.
Comments:
13 pages, 7 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2204.14186 [pdf]
PRD(2022)·19 citations
07
[Submitted on 29 Apr 2022] (cross-list from nucl-ex)
The fast neutron induced fission of $^{240}$ Pu and $^{242}$ Pu
A. Pica · A.T.Chemey · W. Loveland
We report the measurement of the TKE release in the fast neutron induced fission of $^{240}$ Pu and $^{242}$ Pu. The results are compared to the predictions of the GEF model, the CGMF model, and the model of Denisov and Sedykh as well as previous experimental work on these reactions. Our absolute measurements of the TKE release are in good agreement with the previous measurements of Nethaway \textit{et al.} for the interaction of 14.8 MeV neutrons with $^{240}$ Pu \cite{Nethaway} and of Winkelmann and Aumann for the interaction of 15 MeV neutrons with $^{242}$ Pu \cite{Winkelmann}. The general trends of the measured TKE values agree with phenomenological models but the variances of the TKE distributions are significantly less than predicted by various models. The mean post neutron emission TKE release decreases non- linearly with increasing neutron energy and can be represented as TKE(MeV) = 175.8 $\pm$ 0.3 - (2. 4 $\pm$ 0.8)log $_{10}$ E $_{n}$ - (1.4 $\pm$ 0.4)log $_{10}$ E $_{n}^{2}$ for $^{240}$ Pu and TKE(MeV) = 177.1 $\pm$ 0.3 - (1.2 $\pm$ 0.9)log $_{10}$ E $_{n}$ - (1.8 $\pm$ 0.5)log $_{10}$ E $_{n}^{2}$ for $^{242}$ Pu.
Comments:
46 pages, 17 figures
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2204.14246 [pdf]
PRC(2022)·5 citations

Affiliations

first authorsco-authorsvia INSPIRE

Nuclear equation of state for arbitrary proton fraction and temperature based on chiral effective field theory and a Gaussian process emulator

Perturbative QCD and the Neutron Star Equation of State

Predictions of conventional and microscopic triaxial cranking models for light nuclei

Nucleon and Δ resonances in γn→K+Σ− photoproduction

Complete calculation of exclusive heavy vector meson production at next-to-leading order in the dipole picture

Dynamic Magnetic Response of Quark-Gluon Plasma to Electromagnetic Fields

The fast neutron induced fission of 240Pu and 242Pu

Affiliations

Nucleon and $Δ$ resonances in $γ n \to K^{+} Σ^{-}$ photoproduction

The fast neutron induced fission of $^{240}$ Pu and $^{242}$ Pu