Nuclear Theory·nucl-th

Monday·September 16, 2019

9 papers—5 primary·4 cross-listed

01
[Submitted on 12 Sept 2019]
Pseudoscalar glueball mass: a window on three-gluon interactions
E. V. Souza🇧🇷 · M. N. Ferreira🇧🇷 · A. C. Aguilar🇧🇷 · J. Papavassiliou🇪🇸 · C. D. Roberts🇨🇳 · S.-S. Xu🇨🇳
In pure-glue QCD, gluon-gluon scattering in the $J^{P C} = 0^{-+}$ channel is described by a very simple equation, especially if one considers just the leading contribution to the scattering kernel. Of all components in this kernel, only the three-gluon vertex, $V_{μν ρ}$ , is poorly constrained by contemporary analyses; hence, calculations of $0^{-+}$ glueball properties serve as a clear window onto the character and form of $V_{μν ρ}$ . This is important given that many modern calculations of $V_{μν ρ}$ predict the appearance of an infrared suppression in the scalar function which comes to modulate the bare vertex after the nonperturbative resummation of interactions. Such behaviour is a peculiar prediction; but we find that such suppression is essential if one is to achieve agreement with lattice-QCD predictions for the $0^{-+}$ glueball mass. It is likely, therefore, that this novel feature of $V_{μν ρ}$ is real and has observable implications for the spectrum, decays and interactions of all QCD bound-states.
Comments:
6 pages, 4 figures. To appear in Eur. Phys. J. A - Letter
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1909.05875 [pdf]
EPJA(2020)·47 citations
02
[Submitted on 12 Sept 2019]
Towards the Hadron-Quark Continuity Via a Topology Change in Compact Stars
Yong-Liang Ma🇨🇳 · Mannque Rho🇫🇷
We construct a generalized EFT approach to dense compact-star matter that exploits the CCP for hadron-quark continuity at high density, hidden topology and hidden symmetries of QCD. No Landau-Ginzburg-Wilsonian-type phase transition is involved. The microscopic DoF of QCD possibly intervening at high baryonic density are traded in for fractionalized topological objects. Essential in the description are symmetries invisible in QCD in the matter-free vacuum: Scale symmetry, flavor local symmetry and parity-doubling. The partial emergence of scale symmetry is signaled by a dilatonic scalar in a "pseudo-conformal" structure. Flavor gauge symmetry manifests with the $ρ$ meson mass going toward a Wilsonian RGFP identified with the VMFP at which the gauge boson mass goes to zero. Parity doubling is to take place as the quasi-nucleon mass converges to the chiral invariant $m_{0}$ . The theory accounts satisfactorily for all known properties of normal nuclear matter and makes certain predictions that are drastically different from what's available in the literature. In particular, it provides a topological mechanism, argued to be robust, for the cross-over from soft-to-hard EoS that predicts the star properties in overall agreement with the presently available data, including the maximum star mass $M_{ma x} \sim 2.3 M_{⊙}$ and the recent LIGO/Virgo GW data. What is most glaringly different from all other approaches known, however, is the prediction for the rapid convergence to a sound velocity of star $v_{s}^{2} \approx 1/3$ at a density $n \gsim 3 n_{0}$ , far from the asymptotic density $\gsim 50 n_{0}$ expected in pQCD. We interpret this to signal the onset of albeit approximate conformal symmetry in dense compact-star matter. The model developed here could bring out a new paradigm in nuclear/hadron physics, exploiting ideas in condensed matter physics, nuclear and particle physics and astrophysics.
Comments:
Version to appear in Progress in Particle and Nuclear Physics
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1909.05889 [pdf]
PPNP(2020)·84 citations
03
[Submitted on 12 Sept 2019]
Investigating the link between proton reaction cross sections and the quenching of proton spectroscopic factors in $^{48}$ Ca
M. C. Atkinson · W. H. Dickhoff
The nucleon self-energies of $^{40}$ Ca and $^{48}$ Ca are determined using a nonlocal dispersive optical model (DOM). By enforcing the dispersion relation connecting the real and imaginary part of the self-energy, scattering and structure data are used to constrain these self-energies. The ability to calculate both bound and scattering states simultaneously puts these self-energies in a unique position to consistently describe exclusive knockout reactions such as $(e, e^{'} p)$ . The present analysis reveals the importance of high-energy proton reaction cross-section data in constraining spectroscopic factors required for the description of the $(e, e^{'} p)$ cross sections. In particular, it is imperative that high-energy proton reaction cross-section data are measured for $^{48}$ Ca in the near future so that the quenching of the spectroscopic factors in the $^{48}$ Ca $(e, e^{'} p)^{47}$ K reaction can be unambiguously constrained using the DOM. Measurements of proton reaction cross sections in inverse kinematics employing rare isotope beams with large neutron excess will provide corresponding constraints on proton spectroscopic factors for exotic nuclei. Moreover, DOM generated spectral functions indicate that the quenching of spectroscopic factors compared to $^{40}$ Ca is not only due to long-range correlation, but also partly due to the increase in high-momentum protons in $^{48}$ Ca on account of the strong neutron-proton interaction. Single-particle momentum distributions of protons and neutrons in $^{48}$ Ca calculated from these spectral functions confirm that neutron excess causes a higher fraction of high-momentum protons than neutrons.
Comments:
6 pages, 6 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1909.05911 [pdf]
PLB(2019)·32 citations
04
[Submitted on 13 Sept 2019]
The charge-dependent Bonn potentials with pseudovector pion-nucleon coupling
Chencan Wang🇨🇳 · Jinniu Hu🇨🇳 · Ying Zhang · Hong Shen🇨🇳
To apply the high-precision realistic nucleon-nucleon ( $N N$ ) potentials on the investigations of relativistic many-body methods, the new versions of charge-dependent Bonn (CD-Bonn) $N N$ potential are constructed within the pseudovector pion-nucleon coupling instead of the pseudoscalar type in the original CD-Bonn potential worked out by Machleidt [Phys. Rev. C 63, 024001 (2001)]. Two effective scalar mesons are introduced, whose coupling constants with nucleon are independently determined at each partial wave for total angular momentum $J \leq 4$ , to describe the charge dependence of $N N$ scattering data precisely, while the coupling constants between vector, pseudovector mesons and nucleon are identical in all channels. Three revised CD-Bonn potentials adopting the pseudovector pion-nucleon couplings (pvCD-Bonn) are generated by fitting the Nijmegen PWA phase shift data and deuteron binding energy with different pion-nucleon coupling strengths, which can reproduce the phase shifts at spin-single channels and low-energy $N N$ scattering parameters very well, and provide the significantly different mixing parameters at spin-triplet channels. Furthermore, the $D$ -state probabilities of deuteron from these potentials range from $4.22%$ to $6.05%$ . It demonstrates that these potentials contain different components of tensor force, which will be useful to discuss the roles of tensor force in nuclear few-body and many-body systems.
Comments:
33 pages, 9 figures, 18 tables, to be published in Chinese Physics C. The source code of potentials can be required to send an Email to hujinniu@nankai.edu.cn
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1909.06013 [pdf]
CPC(2019)·12 citations
05
[Submitted on 13 Sept 2019]
Statistical-model description of $γ$ decay from compound-nucleus resonances
P. Fanto · Y. Alhassid · H. A. Weidenmüller
The statistical model of compound-nucleus reactions predicts that the fluctuations of the partial $γ$ -decay widths for a compound-nucleus resonance are governed by the Porter-Thomas distribution (PTD), and that consequently the distribution of total $γ$ -decay widths is very narrow. However, a recent experiment [Koehler, Larsen, Guttormsen, Siem, and Guber, Phys. Rev. C 88, 041305(R) (2013)] reported large fluctuations of the total $γ$ -decay widths in the $^{95}$ Mo $(n, γ)^{96}$ Mo* reaction, contrary to this expectation. Furthermore, in recent theoretical works it was argued that sufficiently strong channel couplings can cause deviations of the partial width distributions from PTD. Here, we investigate whether the combined influence of a large number of nonequivalent $γ$ -decay channels, each of which couples weakly to the compound-nucleus resonances, can modify the statistics of the partial widths. We study this effect in neutron scattering off $^{95}$ Mo within a random-matrix model that includes coupling to the entrance neutron channel and to the large number of $γ$ channels. Using realistic coupling parameters obtained from empirical models for the level density and the $γ$ strength function, we find that the PTD describes well the distribution of partial widths for all decay channels, in agreement with the statistical-model expectation. Furthermore, we find that the width of the distribution of the total $γ$ -decay widths is insensitive to wide variations in the parameters of the $γ$ strength function, as well as to deviations of the partial-width distributions from the PTD. Our results rule out an explanation of the recent experimental data within a statistical-model description of the compound nucleus.
Comments:
10 pages, 6 figures. Corresponds to the published version
Subjects:
Nuclear Theory (nucl-th); Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
arXiv:
1909.06250 [pdf]
PRC(2020)·5 citations
06
[Submitted on 13 Sept 2019] (cross-list from nucl-ex)
Status on $^{12} C +^{12} C$ fusion at deep subbarrier energies: impact of resonances on astrophysical $S^{*}$ factors
C. Beck🇫🇷 · A. M. Mukhamedzhanov🇺🇸 · X. Tang🇨🇳
Since the discovery of molecular resonances in $^{12}$ C+ $^{12}$ C in the early sixties a great deal of research work has been undertaken to study $α$ -clustering and resonant effects of the fusion process at sub-Coulomb barrier energies. The modified astrophysical $S^{*}$ factors of $^{12}$ C+ $^{12}$ C fusion have been extracted from direct fusion measurements at deep sub-barrier energies near the Gamow window. They were also obtained by the indirect Trojan horse method (THM). A comparison of direct measurements and the THM, which elucidates problems in the analysis of the THM, is discussed in this Letter to the Editor.
Comments:
5 pages, 3 figures
Subjects:
Nuclear Experiment (nucl-ex); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Theory (nucl-th)
arXiv:
1909.06021 [pdf]
EPJA(2020)·38 citations
07
[Submitted on 12 Sept 2019] (cross-list from hep-ph)
Transport coefficients of hot and dense hadron gas in a magnetic field: a relaxation time approach
Arpan Das🇮🇳 · Hiranmaya Mishra🇮🇳 · Ranjita K. Mohapatra🇮🇳
We estimate various transport coefficients of hot and dense hadronic matter in the presence of magnetic field. The estimation is done through solutions of the relativistic Boltzmann transport equation in the relaxation time approximation.We have investigated the temperature and the baryon chemical potential dependence of these transport coefficients. Explicit calculations are done for the hadronic matter in the ambit of hadron resonance gas model. We estimate thermal conductivity, electrical conductivity and the shear viscosity of hadronic matter in the presence of a uniform magnetic field. Magnetic field, in general, makes the transport coefficients anisotropic. It is also observed that all the transport coefficients perpendicular to the magnetic field are smaller compared to their isotropic counterpart.
Comments:
22 pages, 11 figures. arXiv admin note: text overlap with arXiv:1903.03938
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1909.06202 [pdf]
PRD(2019)·58 citations
08
[Submitted on 13 Sept 2019] (cross-list from hep-ph)
Fierz-complete NJL model study III: Emergence from quark-gluon dynamics
Jens Braun🇩🇪 · Marc Leonhardt🇩🇪 · Martin Pospiech🇩🇪
Our understanding of the dynamics and the phase structure of dense strong-interaction matter is to a large extent still built on the analysis of low-energy models, such as those of the Nambu-Jona-Lasinio-type. In this work, we analyze the emergence of the latter class of models at intermediate and low energy scales from fundamental quark-gluon interactions. To this end, we study the renormalization group flow of a Fierz-complete set of four-quark interactions and monitor their strength at finite temperature and quark chemical potential. At small quark chemical potential, we find that the scalar-pseudoscalar interaction channel is dynamically rendered most dominant by the gauge degrees of freedom, indicating the formation of a chiral condensate. Moreover, the inclusion of quark-gluon interactions leaves a significant imprint on the dynamics as measured by the curvature of the finite-temperature phase boundary which we find to be in accordance with lattice QCD results. At large quark chemical potential, we then observe that the dominance pattern of the four-quark couplings is changed by the underlying quark-gluon dynamics, without any fine-tuning of the four-quark couplings. In this regime, the scalar-pseudoscalar interaction channel becomes subleading and the dominance pattern suggests the formation of a chirally symmetric diquark condensate. In particular, our study confirms the importance of explicit $U_{A} (1)$ breaking for the formation of this type of condensate at high densities.
Comments:
16 pages, 7 figures, 1 table
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1909.06298 [pdf]
PRD(2020)·88 citations
09
[Submitted on 13 Sept 2019] (cross-list from physics.chem-ph)
Efficient evaluation of AGP reduced density matrices
Armin Khamoshi · Thomas Henderson · Gustavo Scuseria
We propose and implement an algorithm to calculate the norm and reduced density matrices of the antisymmetrized geminal power (AGP) of any rank with polynomial cost. Our method scales quadratically per element of the reduced density matrices. Numerical tests indicate that our method is very fast and capable of treating systems with a few thousand orbitals and hundreds of electrons reliably in double-precision. In addition, we present reconstruction formulae that allows one to decompose higher order reduced density matrices in terms of linear combinations of lower order ones, thereby reducing the computational cost significantly.
Subjects:
physics.chem-ph (physics.chem-ph); Strongly Correlated Electrons (cond-mat.str-el); Nuclear Theory (nucl-th)
arXiv:
1909.06345 [pdf]
J.Chem.Phys.(2019)·11 citations

Affiliations

first authorsco-authorsvia INSPIRE