Nuclear Theory·nucl-th

Monday·September 16, 2019

9 papers—5 primary·4 cross-listed

01
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.
nucl-thhep-lathep-phnucl-exEPJA(2020)·47 citations
02
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.
nucl-thhep-phPPNP(2020)·84 citations
03
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.
nucl-thPLB(2019)·32 citations
04
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.
nucl-thCPC(2019)·12 citations
05
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.
nucl-thcond-mat.mes-hallPRC(2020)·5 citations

Affiliations

first authorsco-authorsvia INSPIRE

Pseudoscalar glueball mass: a window on three-gluon interactions

Towards the Hadron-Quark Continuity Via a Topology Change in Compact Stars

Investigating the link between proton reaction cross sections and the quenching of proton spectroscopic factors in 48Ca

The charge-dependent Bonn potentials with pseudovector pion-nucleon coupling

Statistical-model description of γ decay from compound-nucleus resonances

Affiliations

Investigating the link between proton reaction cross sections and the quenching of proton spectroscopic factors in $^{48}$ Ca

Statistical-model description of $γ$ decay from compound-nucleus resonances