Nuclear Theory·nucl-th

Monday·March 1, 2021

9 papers—5 primary·4 cross-listed

01
Jost function formalism with complex potential
K. Mizuyama · T. Dieu Thuy · N. Hoang Tung · D. Quang Tam · T. V. Nhan Hao
The Jost function formalism is extended with use of the complex potential in this paper. We derive the Jost function by taking into account the dual state which is defined by the complex conjugate the complex Hamiltonian. By using the unitarity of the S-matrix which is defined by the Jost function, the optical theorem with the complex potential is also derived. The role of the imaginary part of the complex potential for both the bound states and the scattering states is figured out. The numerical calculation is performed by using the complex Woods-Saxon potential, and some numerical results are demonstrated to confirmed the properties of extended Jost function formalism.
nucl-th0 citations
02
Gamow-Teller transitions of neutron-rich $N = 82, 81$ nuclei by shell-model calculations
Noritaka Shimizu🇯🇵 · Tomoaki Togashi🇯🇵 · Yutaka Utsuno🇯🇵
$β$ -decay half-lives of neutron-rich nuclei around $N = 82$ are key data to understand the $r$ -process nucleosynthesis. We performed large-scale shell-model calculations in this region using a newly constructed shell-model Hamiltonian, and successfully described the low-lying spectra and half-lives of neutron-rich $N = 82$ and $N = 81$ isotones with $Z = 42 - 49$ in a unified way. We found that their Gamow-Teller strength distributions have a peak in the low-excitation energies, which significantly contributes to the half-lives. This peak, dominated by $ν 0 g_{7/2} \to π 0 g_{9/2}$ transitions, is enhanced on the proton deficient side because the Pauli-blocking effect caused by occupying the valence proton $0 g_{9/2}$ orbit is weakened.
nucl-thPTEP(2021)·7 citations
03
Perturbative treatment of three-nucleon force contact terms in three-nucleon Faddeev equations
H. Witała🇵🇱 · J. Golak🇵🇱 · R. Skibiński🇵🇱 · K. Topolnicki🇵🇱
We present a perturbative approach to solving the three-nucleon continuum Faddeev equation. This approach is particularly well suited to dealing with variable strengths of contact terms in a chiral three-nucleon force. We use examples of observables in the elastic nucleon-deuteron scattering as well as in the deuteron breakup reaction to demonstrate high precision of the proposed procedure and its capability to reproduce exact results. A significant reduction of computer time achieved by the perturbative approach in comparison to exact treatment makes this approach valuable for fine-tuning of the three-nucleon Hamiltonian parameters.
nucl-thFew Body Syst.(2021)·9 citations
04
Efimov Physics and Connections to Nuclear Physics
A. Kievsky🇮🇹 · L. Girlanda🇮🇹 · M. Gattobigio🇫🇷 · M. Viviani🇮🇹
Physical systems characterized by a shallow two-body bound or virtual state are governed at large distances by a continuous-scale invariance, which is broken to a discrete one when three or more particles come into play. This symmetry induces a universal behavior for different systems, independent of the details of the underlying interaction, rooted in the smallness of the ratio $ℓ / a_{B} ≪ 1$ , where the length $a_{B}$ is associated to the binding energy of the two-body system $E_{2} = ℏ^{2} / m a_{B}^{2}$ and $ℓ$ is the natural length given by the interaction range. Efimov physics refers to this universal behavior, which is often hidden by the on-set of system-specific non-universal effects. In this work we identify universal properties by providing an explicit link of physical systems to their unitary limit, in which $a_{B} \to \infty$ , and show that nuclear systems belong to this class of universality.
nucl-thcond-mat.quant-gasAnn.Rev.Nucl.Part.Sci.(2021)·47 citations
05
Microscopic analysis of low-energy spin and orbital magnetic dipole excitations in deformed nuclei
V.O. Nesterenko · P.I. Vishnevskiy · J. Kvasil · A. Repko · W. Kleinig
A low-energy magnetic dipole $(M 1)$ spin-scissors resonance (SSR) located just below the ordinary orbital scissors resonance (OSR) was recently predicted in deformed nuclei within the Wigner Function Moments (WFM) approach. We analyze this prediction using fully self-consistent Skyrme Quasiparticle Random Phase Approximation (QRPA) method. Skyrme forces SkM*, SVbas and SG2 are implemented to explore SSR and OSR in $^{160, 162, 164}$ Dy and $^{232}$ Th. Accuracy of the method is justified by a good description of M1 spin-flip giant resonance. The calculations show that isotopes $^{160, 162, 164}$ Dy indeed have at 1.5-2.4 MeV (below OSR) $I^{π} K = 1^{+} 1$ states with a large $M 1$ spin strength ( $K$ is the projection of the total nuclear moment to the symmetry z-axis). These states are almost fully exhausted by $pp [411 ↑, 411 ↓]$ and $nn [521 ↑, 521 ↓]$ spin-flip configurations corresponding to $pp [2 d_{3/2}, 2 d_{5/2}]$ and $nn [2 f_{5/2}, 2 f_{7/2}]$ structures in the spherical limit. So the predicted SSR is actually reduced to low-orbital (l=2,3) spin-flip states. Following our analysis and in contradiction with WFM spin-scissors picture, deformation is not the principle origin of the low-energy spin $M 1$ states but only a factor affecting their features. The spin and orbital strengths are generally mixed and exhibit the interference: weak destructive in SSR range and strong constructive in OSR range. In $^{232}$ Th, the $M 1$ spin strength is found very small. Two groups of $I^{π} = 1^{+}$ states observed experimentally at 2.4-4 MeV in $^{160, 162, 164}$ Dy and at 2-4 MeV in $^{232}$ Th are mainly explained by fragmentation of the orbital strength. Distributions of nuclear currents in QRPA states partly correspond to the isovector orbital-scissors flow but not to spin-scissors one.
nucl-thPRC(2021)·13 citations
06
Fully coupled functional equations for the quark sector of QCD
Fei Gao🇩🇪 · Joannis Papavassiliou🇪🇸 · Jan M. Pawlowski🇩🇪
We present a comprehensive study of the quark sector of $2 + 1$ flavour QCD, based on a self-consistent treatment of the coupled system of Schwinger-Dyson equations for the quark propagator and the full quark-gluon vertex. The individual form factors of the quark-gluon vertex are expressed in a special tensor basis obtained from a set of gauge-invariant operators. The sole external ingredient used as input to our equations is the Landau gauge gluon propagator with $2 + 1$ dynamical quark flavours, obtained from studies with Schwinger-Dyson equations, the functional renormalisation group approach, and large volume lattice simulations. The appropriate renormalisation procedure required in order to self-consistently accommodate external inputs stemming from other functional approaches or the lattice is discussed in detail, and the value of the gauge coupling is accurately determined at two vastly separated renormalisation group scales. Our analysis establishes a clear hierarchy among the vertex form factors. We identify only three dominant ones, in agreement with previous results. The components of the quark propagator obtained from our approach are in excellent agreement with the results from Schwinger-Dyson equations, the functional renormalisation group, and lattice QCD simulation, a simple benchmark observable being the chiral condensate in the chiral limit, which is computed as $(245 MeV)^{3}$ . The present approach has a wide range of applications, including the self-consistent computation of bound-state properties and finite temperature and density physics, which are briefly discussed.
↳ hep-phhep-lathep-thnucl-thPRD(2021)·105 citations
07
Angular Distributions, Polarization Observables, Spin Density Matrices and Statistical Tensors in Photoproduction of Two Pseudoscalar Mesons off a Nucleon
Hiram G. Menendez Santiago🇺🇸
In two meson photoproduction off a nucleon, for the case in which two of the three final state hadrons are products of the decay of an intermediate resonance, general expressions for its decay distribution and for polarization observables are derived in a model independent way. These are functions of either the spin density matrix elements (SDME's) or statistical tensors of the resonance, and the angles of its decay products. The expressions are general enough that it also describes cases where more than one resonance of arbitrary quantum numbers contributes, including interference effects. They can therefore be used to extract the SDME's or statistical tensors of the resonances that contribute to the reaction.
↳ hep-phnucl-th0 citations
08
Test of the nonrelativistic $c c ˉ$ potential
Ulugbek Yakhshiev🇰🇷
We analyze the charmonium states by testing a phenomenological nonrelativistic potential and propose a new set of parameters. This new set of parameters are fixed using only the lowest lying S-wave states of charmonia where the spin-orbit and tensor interactions will not contribute. After fitting the parameters we analyze the whole fine structure of charmonium states taking into account the spin-orbit and tensor interactions too. Calculations showed that the nonrelativistic potential model with the phenomenologically defined parameters is indeed well approximation for describing the charmonium states.
↳ hep-phnucl-thJ.Korean Phys.Soc.(2021)·3 citations
09
Bayesian analysis of multimessenger M-R data with interpolated hybrid EoS
A. Ayriyan🇷🇺 · D. Blaschke🇵🇱 · A. G. Grunfeld🇦🇷 · D. Alvarez-Castillo🇷🇺 · H. Grigorian🇷🇺 · V. Abgaryan🇷🇺
We introduce a family of equations of state (EoS) for hybrid neutron star (NS) matter that is obtained by a two-zone parabolic interpolation between a soft hadronic EoS at low densities and a set of stiff quark matter EoS at high densities within a finite region of chemical potentials $μ_{H} < μ < μ_{Q}$ . Fixing the hadronic EoS as the APR one and choosing the color-superconducting, nonlocal NJL model with two free parameters for the quark phase, we perform Bayesian analyses with this two-parameter family of hybrid EoS. Using three different sets of observational constraints that include the mass of PSR J0740+6620, the tidal deformability for GW170817, and the mass-radius relation for PSR J0030+0451 from NICER as obligatory (set 1), while set 2 uses the possible upper limit on the maximum mass from GW170817 as an additional constraint and set 3 instead of the possibility that the lighter object in the asymmetric binary merger GW190814 is a neutron star. We confirm that in any case, the quark matter phase has to be color superconducting with the dimensionless diquark coupling approximately fulfilling the Fierz relation $η_{D} = 0.75$ and the most probable solutions exhibiting a proportionality between $η_{D}$ and $η_{V}$ , the coupling of the repulsive vector interaction that is required for a sufficiently large maximum mass. We used the Bayesian analysis to investigate with the method of fictitious measurements the consequences of anticipating different radii for the massive $2 M_{⊙}$ PSR J0740+6220 for the most likely equation of state. With the actual outcome of the NICER radius measurement on PSR J0740+6220 we could conclude that for the most likely hybrid star EoS would not support a maximum mass as large as $2.5 M_{⊙}$ so that the event GW190814 was a binary black hole merger.
↳ astro-ph.HEhep-phnucl-thEPJA(2021)·64 citations

Affiliations

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