Nuclear Theory·nucl-th

Monday·July 15, 2019

12 papers—8 primary·4 cross-listed

01
[Submitted on 11 Jul 2019]
Correlations between azimuthal anisotropy Fourier harmonics in PbPb collisions at $s_{_{NN}} = 2.76$ TeV in the HYDJET++ and AMPT models
M. Dordevic🇷🇸 · J. Milosevic🇷🇸 · L. Nadderd🇷🇸 · M. Stojanovic🇷🇸 · F. Wang🇺🇸 · X. Zhu🇨🇳
Correlations between azimuthal anisotropy Fourier harmonics $v_{n}$ ( $n = 2, 3, 4$ ) are studied using the events from PbPb collisions at $s_{_{NN}} = 2.76$ TeV generated by the HYDJET++ and AMPT models, and compared to the corresponding experimental results obtained by the ATLAS Collaboration. The Fourier harmonics $v_{n}$ are measured over a wide centrality range using the two-particle azimuthal correlation method. The slopes of the $v_{2}$ -- $v_{3}$ correlation from both models are in a good agreement with the ATLAS data. The HYDJET++ model predicts a stronger slope for the $v_{2}$ -- $v_{4}$ and $v_{3}$ -- $v_{4}$ correlations than the ones experimentally measured, while the results from the AMPT model are in a rather good agreement with the experimental results. In contrast to the HYDJET++ predictions, the AMPT model predicts a boomerang-like shape in the structure of the correlations as found in the experimental data.
Comments:
10 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1907.05450 [pdf]
PRC(2020)·7 citations
02
[Submitted on 11 Jul 2019]
On the Cottingham formula and the electromagnetic contribution to the proton-neutron mass splitting
Andre Walker-Loud🇺🇸
The excess mass of the neutron over the proton arises from two sources within the Standard Model, electromagnetism and the splitting of the down and up quark masses. The Cottingham Formula provides a means of determining the QED corrections from the forward Compton Amplitude, but this is challenged by the need for a subtraction function and the mixing of the QED and QCD (electro-weak) effects. I review the present understanding of the Cottingham Formula, including a discussion on the development of the formula, its renormalization which induces the mixing of QED and QCD effects, and the necessary modeling of the subtraction function that must be done to arrive a numerical prediction. I summarize the Regge Model originally proposed by Gasser and Leutwyler and I also review the proposed model by Walker-Loud, Carlson and Miller, which is an interpolation function between the low and high $Q^{2}$ regimes, both of which are anchored by rigorous theoretical underpinnings, for which I argue a more reliable theoretical uncertainty estimate can be obtained.
Comments:
The 9th International workshop on Chiral Dynamics
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1907.05459 [pdf]
PoS(2019)·10 citations
03
[Submitted on 11 Jul 2019]
Variational approximations to exact solutions in shell-model valence spaces: calcium isotopes in the pf-shell
B. Bally · A. Sánchez-Fernández · T. R. Rodríguez
We study the performance of self-consistent mean-field and beyond-mean-field approximations in shell-model valence spaces. In particular, Hartree-Fock-Bogolyubov, particle-number variation after projection and projected generator coordinate methods are applied to obtain ground-state and excitation energies for even-even and odd-even Calcium isotopes in the pf-shell. The standard (and non-trivial) KB3G nuclear effective interaction has been used. The comparison with the exact solutions -- provided by the full diagonalization of the Hamiltonian -- shows an outstanding agreement when particle-number and angular-momentum restorations are performed and both quadrupole and neutron-neutron pairing degrees of freedom are explicitly explored as collective coordinates.
Comments:
14 pages, 10 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1907.05493 [pdf]
PRC(2019)·37 citations
04
[Submitted on 12 Jul 2019]
Decoherence of collective motion in warm nuclei
S. Frauendorf🇺🇸 · C. M. Petrache🇫🇷 · R. Schwengner🇩🇪 · K.Wimmer🇯🇵
Collective states in cold nuclei are represented by a wave function that assigns coherent phases to the participating nucleons. The degree of coherence decreases with excitation energy above the yrast line because of coupling to the increasingly dense background of quasiparticle excitations. The consequences of decoherence are discussed, starting with the well studied case of rotational damping. In addition to superdeformed bands, a highly excited oblate band is presented as a new example of screening from rotational damping. Suppression of pair correlation leads to incoherent thermal M1 radiation, which appears as an exponential spike (LEMAR) at zero energy in the $γ$ strength function of spherical nuclei. In deformed nuclei a Scissors Resonance appears and LEMAR changes to damped magnetic rotation, which is interpreted as partial restoration of coherence.
Comments:
Proceedings of the conference on Nuclear structure and dynamics 2019
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1907.05569 [pdf]
EPJ Web Conf.(2019)·1 citation
05
[Submitted on 12 Jul 2019]
Post-formation in alpha emission from nuclei
Junki Tanaka · Carlos Bertulani · Stefan Typel
We propose a novel mechanism to explain nuclear decay by emission of an alpha particle. We show that the famous Geiger-Nuttall law can be explained by post-forming an alpha particle outside the range of the nuclear interaction with the daughter nucleus. This contrasts with the commonly accepted mechanism of first alpha particle pre-formation followed by emission through barrier penetration. We predict that the post-formation mechanism is more likely to occur for alpha-particles with higher energy.
Comments:
12 pages, 3 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1907.05574 [pdf]
EPJ Web Conf.(2020)·1 citation
06
[Submitted on 12 Jul 2019]
Origin of energy shift in kaonic atom and kaon-nucleus interaction
Yutaro Iizawa🇯🇵 · Daisuke Jido🇯🇵 · Natsumi Ikeno🇯🇵 · Junko Yamagata-Sekihara🇯🇵 · Satoru Hirenzaki🇯🇵
The $K^{-}$ -nucleus optical potential is revisited to investigate its global feature phenomenologically. It is a puzzle that the energy shift is found to be repulsive in all of the observed kaonic atom, although the $K^{-} N$ interaction is known to be so attractive as to form the $Λ (1405)$ resonance. To solve this puzzle, we examine the $K^{-}$ optical potential in the linear density approximation and determine the potential parameters of each kaonic atom so as to reproduce the observed energy shift and absorption width. We find two types of the potentials. One potential has a so large real part as to provide nuclear states with the same quantum number to the atomic state in the last orbit. The level repulsion between the atomic state and the nuclear states takes place due to their mixing, and it makes the atomic state shifted repulsively. The other type of the potential has a large imaginary part and the imaginary part works repulsively for atomic states. We find that only the latter solution reproduce a wide of the observed data, and thus is realized as a $K^{-}$ -nucleus potential for kaonic atom. In the linear nuclear density optical potential, the picture that the repulsive shifts in the atomic states stem from the existence of the nuclear states does not globally stand up. This implies that the $K^{-}$ -nucleus optical potential should have a large imaginary part. We examine some nonlinear density effects and find that the conclusion does not change. We also confirm that the conventionally known optical potentials are categorized into the latter type of the potential.
Comments:
12 pages, 16 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1907.05626 [pdf]
0 citations
07
[Submitted on 12 Jul 2019]
Deuteron wave function for Reid93 potential and polarization observables in elastic lepton-deuteron scattering
V.I. Zhaba🇺🇦
Elastic lepton-deuteron scattering was considered within the limit of zero lepton mass. The deuteron wave function in the coordinate representation for the Reid93 potential was applied to numerical calculations. The angular-momentum dependence of values spin correlation coefficients $C_{x z}^{(0)}$ , $C_{z z}^{(0)}$ and tensor asymmetries $A_{xx}^{(0)}$ , $A_{x z}^{(0)}$ , $A_{z z}^{(0)}$ have been evaluated in 3D format for Reid93 potential. These polarization observables are analyzed for different energies and scattering angles. Application of the obtained values allows better explanation and illustration of the laws of elastic lepton-deuteron scattering.
Comments:
14 pages, 5 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1907.05726 [pdf]
IJMPE(2019)·4 citations
08
[Submitted on 12 Jul 2019]
Symmetric nuclear matter from the strong interaction
M. Leonhardt🇩🇪 · M. Pospiech🇩🇪 · B. Schallmo🇩🇪 · J. Braun🇩🇪 · C. Drischler🇺🇸 · K. Hebeler🇩🇪 · A. Schwenk🇩🇪
We study the equation of state of symmetric nuclear matter at zero temperature over a wide range of densities using two complementary theoretical approaches. At low densities up to twice nuclear saturation density, we compute the energy per particle based on modern nucleon-nucleon and three-nucleon interactions derived within chiral effective field theory. For higher densities we derive for the first time constraints in a Fierz-complete setting directly based on quantum chromodynamics using functional renormalization group techniques. We find remarkable consistency of the results obtained from both approaches as they come together in density and the natural emergence of a maximum in the speed of sound $c_{S}$ at supranuclear densities with a value beyond the asymptotic $c_{S}^{2} = 1/3$ . The presence of a maximum appears tightly connected to the formation of a diquark gap.
Comments:
7 pages, 2 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1907.05814 [pdf]
PRL(2020)·135 citations

Affiliations

first authorsco-authorsvia INSPIRE