Nuclear Theory·nucl-th

Tuesday·April 7, 2020

17 papers—11 primary·6 cross-listed

01
[Submitted on 2 Apr 2020]
Comment on the paper Eur. Phys. J. A (2019) 55:150
C. Gonzalez-Boquera · M. Centelles · X. Viñas L.M. Robledo
The conclusions of the study published as Eur. Phys. J. A (2019) 55:150 questioning the adequacy of the recently proposed Gogny D1M* interaction for finite-nuclei calculations using harmonic oscillator (HO) basis are revised. The existence of an instability in finite nuclei for D1M* when coordinate-space methods are used to solve the HF equations (as shown in Eur. Phys. J. A(2019) 55:150) is independently confirmed using a computer code based on a quasi-local approximation (QLA) to the HF energy density with finite-range forces. We confirm that the most affected quantity in the coordinate-space calculation is the spatial density at the origin. Our study reveals that some findings concerning these instabilities are not easy to reconcile with the arguments used in Eur. Phys. J. A (2019) 55:150. For instance, some nuclei such as $^{4}$ He and $^{40}$ Ca, which diverge in HF mesh-point calculations performed with D1M*, become perfectly stable when Coulomb force is switched off. We have also found instabilities in some nuclei when the D1M interaction is used. Finally, a connection between the occupancy of $s$ -orbitals near the Fermi level and the appearance of instabilities is observed. Several convergence and stability studies are performed with HO basis of different sizes and oscillator parameters to demonstrate the robustness of the D1M* results for finite nuclei when the HO basis is used.
Comments:
6 pages, 6 figures. arXiv admin note: text overlap with arXiv:1807.10159; Summary and conclusions added
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2004.01701 [pdf]
2 citations
02
[Submitted on 3 Apr 2020]
Threshold $π^{-}$ Photoproduction on the Neutron
W.J. Briscoe (GWU)🇺🇸 · A.E. Kudryavtsev (ITEP)🇺🇸 · I.I. Strakovsky (GWU)🇺🇸 · V.E. Tarasov (ITEP)🇷🇺 · R.L. Workman (GWU)🇺🇸
Recent data from the PIONS $@$ MAX-lab Collaboration, measuring the total cross section of the pion incoherent photoproduction $γ d \to π^{-} pp$ near threshold, have been used to extract the E $_{0 +}$ multipole and total cross section of the reaction $γ n \to π^{-} p$ , also near threshold. These are the first measurements of the reaction $γ d \to π^{-} pp$ in the threshold region. The value of E $_{0 +}$ is extracted through a fit to the deuteron data in a photoproduction model accounting for final-state interactions. The model takes an $S$ -wave approximation for the elementary reaction $γ n \to π^{-} p$ with E $_{0 +} =$ const in the threshold region. The obtained value E $_{0 +} = - 31.86 \pm 0.8$ (in $1 0^{- 3} / m_{π^{+}}$ units) is in agreement with other existing results. Model predictions for the total cross section $σ (γ n \to π^{-} p)$ are also given.
Comments:
7 pages, 4 figures, 2 tables
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
2004.01742 [pdf]
EPJA(2020)·16 citations
03
[Submitted on 3 Apr 2020]
Many-body Dyson equation approach to the seniority model of pairing
Peter Schuck🇫🇷
As is well known, the single level seniority model of pairing has been solved exactly since long using angular momentum algebra. It is shown that it can also be solved using the Dyson equation of standard many-body theory. The formalism shows some interesting many-body aspects.
Subjects:
Nuclear Theory (nucl-th); Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Superconductivity (cond-mat.supr-con)
arXiv:
2004.01763 [pdf]
IJMPE(2020)·1 citation
04
[Submitted on 3 Apr 2020]
Correlation between mean transverse momentum and anisotropic flow in heavy-ion collisions
Giuliano Giacalone🇫🇷 · Fernando G. Gardim🇧🇷 · Jacquelyn Noronha-Hostler🇺🇸 · Jean-Yves Ollitrault🇫🇷
The correlation between the mean transverse momentum of outgoing particles, $⟨ p_{t} ⟩$ , and the magnitude of anisotropic flow, $v_{n}$ , has recently been measured in Pb+Pb collisions at the CERN Large Hadron Collider, as a function of the collision centrality. We confirm the previous observation that event-by-event hydrodynamics predicts a correlation between $v_{n}$ and $⟨ p_{t} ⟩$ that is similar to that measured in data. We show that the magnitude of this correlation can be directly predicted from the initial condition of the hydrodynamic calculation, for $n = 2, 3$ , if one replaces $v_{n}$ by the corresponding initial-state anisotropy, $ε_{n}$ , and $⟨ p_{t} ⟩$ by the total energy per unit rapidity of the fluid at the beginning of the hydrodynamic expansion.
Comments:
7 pages; 4 figures; v2: published version
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
2004.01765 [pdf]
PRC(2021)·83 citations
05
[Submitted on 5 Apr 2020]
Secondary $γ$ -ray decays from the partial-wave $T$ matrix with an $R$ -matrix application to $^{15} N (p, α_{1} γ)^{12} C$
Carl R. Brune · R. James deBoer
The secondary $γ$ rays emitted following a nuclear reaction are often relatively straightforward to detect experimentally. Despite the large volume of such data, a practical formalism for describing these $γ$ rays in terms of partial-wave $T$ -matrix elements has never been given. The partial-wave formalism is applicable when $R$ -matrix methods are used to describe the reaction in question. This paper supplies the needed framework, and it is demonstrated by the application to the $^{15} N (p, α_{1} γ)^{12} C$ reaction.
Comments:
7 pages, 1 figure
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2004.02246 [pdf]
PRC(2020)·5 citations
06
[Submitted on 6 Apr 2020]
Elastic $α$ - $^{12}$ C scattering at low energies with the sharp resonant $0_{3}^{+}$ state of $^{16}$ O
Shung-Ichi Ando (Sunmoon U.)
An inclusion of sharp resonant $0_{3}^{+}$ state of $^{16}$ O and first excited $2_{1}^{+}$ state of $^{12}$ C in a study of $s$ -wave elastic $α$ - $^{12}$ C scattering at low energies is investigated in an effective Lagrangian approach. The elastic scattering amplitude is parted into two; one is for the sharp resonant $0_{3}^{+}$ state of $^{16}$ O parameterized by Breit-Wigner formula, and the other is for a non-resonant part of the amplitude parameterized by effective range expansion. In the non-resonant part of the amplitude, a contribution from the $2_{1}^{+}$ state of $^{12}$ C is included. We discuss a large correlation between a coupling for the $2_{1}^{+}$ state of $^{12}$ C and an effective range parameter $Q_{0}$ as well as a necessity of inclusion of a vertex correction for the initial and final $α$ - $^{12}$ C states. After fixing parameters appearing in the amplitudes by using experimental data, we calculate asymptotic normalization coefficients for ground $0_{1}^{+}$ state and first excited $0_{2}^{+}$ state of $^{16}$ O and compare them to previous results found in literature.
Comments:
14 pages, 4 eps figures, version accepted for publication in Phys. Rev. C
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2004.02361 [pdf]
PRC(2020)·5 citations
07
[Submitted on 6 Apr 2020]
Solitons in nuclear time-dependent density functional theory
Yoritaka Iwata
The soliton existence in sub-atomic many-nucleon systems is discussed. In many nucleon dynamics represented by the nuclear time-dependent density functional formalism, much attention is paid to energy and mass dependence of the soliton existence. In conclusion, the existence of nuclear soliton is clarified if the temperature of nuclear system is from 10 to 30 MeV. With respect to the mass dependence $^{4}$ He and $^{16}$ O are suggested to be the candidates for the self-bound states exhibiting the property of nuclear soliton.
Comments:
[Invited] submitted to "Frontiers in Physics"
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2004.02409 [pdf]
Front.Phys.(2020)·1 citation
08
[Submitted on 6 Apr 2020]
Prediction of the analyzing power for $p$ + $^{6}$ He elastic scattering at 200 MeV from $p$ + $^{4}$ He elastic scattering at 200 MeV
Masahiro Ishii · Yasunori Iseri · Masanobu Yahiro
We apply the cluster-folding (CF) model for $p +^{6}$ He scattering at 200 MeV, where the potential between $p$ and $^{4}$ He is fitted to data on $p +^{4}$ He scattering at 200 MeV. For $p +^{6}$ He scattering at 200 MeV, the CF model reproduces measured differential cross section with no free parameter, We then predict the analyzing power $A_{y} (q)$ with the CF model, where $q$ is the transfer momentum. Johnson, Al-Khalili and Tostevin construct a theory for one-neutron halo scattering, taking (1) the adiabatic approximation and (2) neglecting the interaction between a valence neutron and a target, and yield a simple relationship between the elastic scattering of a halo nucleus and of its core under certain conditions. We improve their theory with (3) the eikonal approximation in order to determine $A_{y} (q)$ for $^{6}$ He from the data on $A_{y} (q)$ for $^{4}$ He. The improved theory is accurate, when approximation (1)--(3) are good. Among the three approximations, approximation (2) is most essential. The CF model shows that approximation (2) is good in $0.9 < q < 2.4$ fm $^{- 1}$ . In the improved theory, the $A_{y} (q)$ for $^{6}$ He is the same as that for $^{4}$ He. In $0.9 < q < 2.4$ fm $^{- 1}$ , we then predict $A_{y} (q)$ for $p +^{6}$ He scattering at 200 MeV from measured $A_{y} (q)$ for $p +^{4}$ He scattering at 200 MeV. We thus predict $A_{y} (q)$ with the model-dependent and the model-independent prescription. The ratio of differential cross sections measured for $^{6}$ He to that for $^{4}$ He is related to the wave function of $^{6}$ He. We then determine the radius between $^{4}$ He and the center-of-mass of valence two neutrons in $^{6}$ He. The radius is 5.77 fm.
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2004.02419 [pdf]
PRC(2021)·0 citations
09
[Submitted on 6 Apr 2020]
Recent Progress in Basis Light-front Quantization
Xingbo Zhao🇨🇳 · Kaiyu Fu🇨🇳 · Hengfei Zhao🇨🇳 · Jiangshan Lan🇨🇳 · Chandan Mondal🇨🇳 · Siqi Xu🇨🇳 · James P. Vary (BLFQ Collaboration)🇺🇸
Basis Light-front Quantization (BLFQ) is a nonperturbative approach to quantum field theory. In this paper, we report our recent progress in applying BLFQ to the positronium system in QED and to the meson and the baryon system in QCD. We present preliminary results on the mass spectrum, light-front wave functions and other observables of these systems, where one dynamical gauge boson is retained for the positronium and meson systems.
Comments:
8 pages, 6 figues, proceeding for the 18th International Conference on Hadron Spectroscopy and Structure (HADRON2019)
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2004.02456 [pdf]
3 citations
10
[Submitted on 6 Apr 2020]
Relativistic hydrodynamics for spin-polarized media
Radoslaw Ryblewski🇵🇱 · Rajeev Singh🇵🇱
We summarize the key ingredients of the recently proposed formalism of relativistic perfect-fluid hydrodynamics with spin. Based on the underlying kinetic theory definitions for the equilibrium distribution functions we obtain the evolution equations governing the system's expansion. Employing Bjorken symmetry we study the spin polarization dynamics of the system.
Comments:
Presented by Radoslaw Ryblewski at XXVI Cracow Epiphany Conference, LHC Physics: Standard Model and Beyond, January 7-10, 2020, Krakow, Poland.; 11 pages, 5 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2004.02544 [pdf]
Acta Phys.Polon.B(2020)·2 citations
11
[Submitted on 6 Apr 2020]
Fluctuation dynamics near the QCD critical point
Lipei Du🇺🇸 · Ulrich Heinz🇺🇸 · Krishna Rajagopal🇺🇸 · Yi Yin🇺🇸
The evolution of non-hydrodynamic slow processes near the QCD critical point is explored with the novel Hydro+ framework, which extends the conventional hydrodynamic description by coupling it to additional explicitly evolving slow modes describing long wavelength fluctuations. Their slow relaxation is controlled by critical behavior of the correlation length and is independent from gradients of matter density and pressure that control the evolution of the hydrodynamic quantities. In this exploratory study we follow the evolution of the slow modes on top of a simplified QCD matter background, allowing us to clearly distinguish, and study both separately and in combination, the main effects controlling the dynamics of critical slow modes. In particular, we show how the evolution of the slow modes depend on their wave number, the expansion of and advection by the fluid background, and the behavior of the correlation length. Non-equilibrium contributions from the slow modes to bulk matter properties that affect the bulk dynamics (entropy, pressure, temperature and chemical potential) are discussed and found to be small.
Comments:
29 pages, 18 figures. Some discussions are added; Fig. 1 is separated into two figures; in some figures, axis labels and line color styles are updated. Published as Phys. Rev. C 102, 054911 (2020)
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Experiment (nucl-ex)
arXiv:
2004.02719 [pdf]
PRC(2020)·62 citations

Affiliations

first authorsco-authorsvia INSPIRE