Nuclear Theory·nucl-th

Thursday·February 28, 2019

9 papers—3 primary·6 cross-listed

01
[Submitted on 27 Feb 2019]
$α$ and triton clustering in $^{35}$ Cl
Yasutaka Taniguchi
Coupling of cluster and deformed structures are important for dynamics of nuclear structure. Threshold energy has been discussed to explain cluster structures coupling to deformed states but relation between threshold energy and excitation energy has open problems. Negative-parity superdeformed (SD) states were observed by a $γ$ -spectroscopy experiment in $^{35}$ Cl but its detailed structure is unclear. By analyzing coupling of cluster structures in deformed states and high-lying cluster states in $^{35}$ Cl, cluster structures coupling to deformed states and excitation energy of high-lying cluster states are investigated. The antisymmetrized molecular dynamics (AMD) and the generator coordinate method (GCM) are used. An AMD wave function is a Slater determinant of Gaussian wave packets. By energy variational calculations with constraints on deformation and clustering, wave functions of deformed structures and $α$ - and $t$ -cluster structures are obtained. Adopting those wave functions as GCM basis, wave functions of ground and excited states are calculated. Various deformed bands are obtained and predicted. A $K^{π} = \frac{1}{2}^{-}$ deformed band, which corresponds to the observed SD band, dominates deformed structure and compact $α$ - and $t$ -cluster structure components. Particle-hole configurations of the dominant components with deformed and cluster structures are similar. In high-lying states, almost pure $α$ - and $t$ -cluster states are obtained in negative-parity states, and excitation energies of the $t$ -cluster states are higher than those of $α$ -cluster states. In conclusions, particle-hole configurations of cluster structure with small intercluster distance are important for coupling to low-energy deformed states. Threshold energies reflect to excitation energies of high-lying almost pure cluster states.
Comments:
19 pages, 8 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1902.10428 [pdf]
PRC(2019)·4 citations
02
[Submitted on 28 Nov 2018]
Hadron Formation From Quark-Gluon Plasma Using Lattice QCD At Finite Temperature
Gouranga C Nayak
Recently we have reported the correct formulation of the lattice QCD method at the zero temperature to study the hadron formation from the quarks and gluons by incorporating the non-zero boundary surface term in QCD which arises due to the confinement of quarks and gluons inside the finite size hadron. In this paper we extend this to the finite temperature QCD and present the correct formulation of the lattice QCD method at the finite temperature to study the hadron formation from the quark-gluon plasma.
Comments:
12 pages latex
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1902.10522 [pdf]
7 citations
03
[Submitted on 27 Feb 2019]
Ab initio calculations of 5H resonant states
R. Lazauskas🇫🇷 · E. Hiyama🇯🇵 · J. Carbonell🇫🇷
By solving the 5-body Faddeev-Yakubovsky equations in configuration space with realistic nuclear Hamiltonians we have studied the resonant states of $^{5}$ H isotope. Two different methods, allowing to bypass the exponentially diverging boundary conditions, have been employed providing consistent results. The existence of $^{5}$ H broad J $^{π}$ =1/2 $^{+}$ ,3/2 $^{+}$ ,5/2 $^{+}$ states as S-matrix poles has been confirmed and compared with the, also calculated, resonant states in $^{4}$ H isotope. We have established that the positions of these resonances only mildly depend on the nuclear interaction model.
Comments:
to appear in Physics Letters B (2019)
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex); Computational Physics (physics.comp-ph)
arXiv:
1902.10553 [pdf]
PLB(2019)·25 citations
04
[Submitted on 26 Feb 2019] (cross-list from hep-ph)
Quark mass dependence of $γ^{*} π \to π π$
Malwin Niehus🇩🇪 · Martin Hoferichter🇺🇸 · Bastian Kubis🇩🇪
Usually the simulation of scattering processes in lattice QCD is carried out at unphysically high values of the quark masses. Hence, a method to extrapolate data obtained in lattice calculations to physical masses is needed to allow for comparison between theory and experiment. To obtain a sound extrapolation, dispersion relations and chiral perturbation theory can be invoked. While a simple combined approach known as the inverse amplitude method allows for a successful extrapolation of $π π \to π π$ data, a more complicated framework is needed for inelastic processes such as $γ^{*} π \to π π$ . By employing a well-established dispersive description, the extrapolation can be performed for $γ^{*} π \to π π$ both for on-shell as well as virtual photons, the decay $γ^{*} \to π π π$ is also within the range of applicability. This particular process is interesting due to both its contribution to the anomalous magnetic moment of the muon and its connection to the axial anomaly.
Comments:
10 pages, 2 figures, proceedings for The 9th International Workshop on Chiral Dynamics, Durham, North Carolina, USA, September 17-21, 2018
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
1902.10150 [pdf]
PoS(2019)·13 citations
05
[Submitted on 26 Feb 2019] (cross-list from hep-ph)
Electromagnetic multipole moments of baryons
Alfons J. Buchmann🇩🇪
We calculate the charge quadrupole and magnetic octupole moments of baryons using a group theoretical approach based on broken SU(6) spin-flavor symmetry. The latter is an approximate symmetry of the QCD Lagrangian which becomes exact in the large color N_c limit. Spin-flavor symmetry breaking is induced by one-, two-, and three-quark terms in the electromagnetic current operator. Two- and three-quark currents provide the leading contributions for higher multipole moments, despite being of higher order in an 1/N_c expansion. Our formalism leads to relations between N --> N* transition multipole moments and nucleon ground state properties. We compare our results to experimental quadrupole and octupole transition moments extracted from measured helicity amplitudes.
Comments:
18 pages, 8 figures, Talk given at NSTAR 2017, 11th International Workshop on the Physics of Excited Nucleons, Aug. 20-23, 2017, Columbia, SC, USA
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1902.10166 [pdf]
Few Body Syst.(2018)·9 citations
06
[Submitted on 27 Feb 2019] (cross-list from hep-lat)
Constraints on Disconnected Contributions in $π π$ Scattering
N. Ripunjay Acharya🇩🇪 · Feng-Kun Guo🇨🇳 · Ulf-G. Meißner🇩🇪 · Chien-Yeah Seng🇩🇪
The accuracy of the lattice QCD computation of hadron-hadron scattering at low isospin depends critically on the ability to compute correlation functions with fermionic disconnected Wick contractions. This happens, for instance, in isospin $I = 0$ $π π$ scattering, which receives contributions from rectangular and vacuum types of contractions among other easier calculable ones. Combining Lüscher's formula and partially-quenched chiral perturbation theory, we provide precise theory predictions of the discrete energy levels extracted from specific linear combinations of lattice correlation functions corresponding to various types of contractions. Expressions are provided for extracting the unphysical low-energy constants in the partially-quenched chiral perturbation theory from the energy levels for these contractions. The predictions for the rectangular and vacuum contractions may serve as solid tests of the accuracy for existing and future lattice studies of $π π$ scattering.
Comments:
Version to appear in JHEP
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1902.10290 [pdf]
JHEP(2019)·6 citations
07
[Submitted on 27 Feb 2019] (cross-list from hep-ph)
Aspects of quarkonium propagation in a thermal medium as seen by string models
Oleg Andreev🇷🇺
We use gauge/string duality to model a heavy quark-antiquark pair in a color singlet moving through a thermal plasma. In particular, we explore the effect of velocity on the string tension and Debye screening mass. Then we apply the results to the analysis of heavy quarkonium bound states. With some assumptions, we estimate the characteristic size of quarkonium and its dissociation temperature.
Comments:
17 pages, 8 figures; v2: improved presentation and discussion, typos corrected, references added
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
1902.10458 [pdf]
PRD(2019)·4 citations
08
[Submitted on 27 Feb 2019] (cross-list from hep-ph)
Flavor decomposition of the pion-nucleon $σ$ -term
Daniel Severt🇩🇪 · Ulf-G. Meißner🇩🇪 · Jambul Gegelia🇬🇪
We re-analyze the flavor decomposition of the pion-nucleon $σ$ -term in the framework of baryon chiral perturbation to fourth order. We employ a covariant and the heavy baryon framework including also the low-lying decuplet. Using only continuum data, we find a small strangeness content of the proton. The uncertainties are, however, large and might be overcome by dedicated lattice QCD calculations.
Comments:
31 pages, 1 figure, published version, some minor modifications
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
1902.10508 [pdf]
JHEP(2019)·12 citations
09
[Submitted on 27 Feb 2019] (cross-list from nucl-ex)
Exposing Novel Quark and Gluon Effects in Nuclei
I. C. Cloët🇺🇸 · R. Dupré🇫🇷 · S. Riordan🇺🇸 · W. Armstrong🇺🇸 · J. Arrington🇺🇸 · W. Cosyn🇧🇪 · N. Fomin🇺🇸 · A. Freese🇺🇸 · S. Fucini🇮🇹 · D. Gaskell🇺🇸 · C. E. Keppel🇺🇸 · G. A. Miller🇺🇸 and 6 other authors
The fundamental theory of the strong interaction -- quantum chromodynamics (QCD) -- provides the foundational framework with which to describe and understand the key properties of atomic nuclei. A deep understanding of the explicit role of quarks and gluons in nuclei remains elusive however, as these effects have thus far been well-disguised by confinement effects in QCD which are encapsulated by a successful description in terms of effective hadronic degrees of freedom. The observation of the EMC effect has provided an enduring indication for explicit QCD effects in nuclei, and points to the medium modification of the bound protons and neutrons in the nuclear medium. Understanding the EMC effect is a major challenge for modern nuclear physics, and several key questions remain, such as understanding its flavor, spin, and momentum dependence. This manuscript provides a contemporary snapshot of our understanding of the role of QCD in nuclei and outlines possible pathways in experiment and theory that will help deepen our understanding of nuclei in the context of QCD.
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1902.10572 [pdf]
J.Phys.G(2019)·38 citations

Affiliations

first authorsco-authorsvia INSPIRE