Nuclear Theory·nucl-th

Monday·May 30, 2016

8 papers—5 primary·3 cross-listed

01
[Submitted on 27 May 2016]
Electric dipole response of neutron-rich Calcium isotopes in relativistic quasiparticle time blocking approximation
Irina A. Egorova🇺🇸 · Elena Litvinova🇺🇸
New results for electric dipole strength in the chain of even-even Calcium isotopes with the mass numbers A = 40 - 54 are presented. Starting from the covariant Lagrangian of Quantum Hadrodynamics, spectra of collective vibrations (phonons) and phonon-nucleon coupling vertices for $J \leq 6$ and normal parity were computed in a self-consistent relativistic quasiparticle random phase approximation (RQRPA). These vibrations coupled to Bogoliubov two-quasiparticle configurations (2q $\otimes$ phonon) form the model space for the calculations of the dipole response function in the relativistic quasiparticle time blocking approximation (RQTBA). The results for giant dipole resonance in the latter approach are compared to those obtained in RQRPA and to available data. Evolution of the dipole strength with neutron number is investigated for both high-frequency giant dipole resonance (GDR) and low-lying strength. Development of a pygmy resonant structure on the low-energy shoulder of GDR is traced and analyzed in terms of transition densities. A dependence of the pygmy dipole strength on the isospin asymmetry parameter is extracted.
Comments:
Article: 9 pages, 5 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1605.08482 [pdf]
PRC(2016)·47 citations
02
[Submitted on 27 May 2016]
Spectroscopic factor strengths using $ab ini t i o$ approaches
P. C. Srivastava · Vikas Kumar
We have calculated the spectroscopic factor strengths for the one-proton and one-neutron pick-up reactions $^{27}$ Al( $d$ , $^{3}$ He) $^{26}$ Mg and $^{27}$ Al( $d$ , $t$ ) $^{26}$ Al within the framework of the shell model. We employed two different $ab ini t i o$ approaches : an in-medium similarity renormalization targeted for a particular nucleus, and the coupled- cluster effective interaction. We also compared our results with recently determined experimental spectroscopic factors.
Comments:
7 pages, 4 figures, 4 tables
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1605.08508 [pdf]
PRC(2016)·13 citations
03
[Submitted on 27 May 2016]
Simultaneous analysis of matter radii, transition probabilities, and excitation energies of Mg isotopes by angular-momentum-projected configuration-mixing calculations
Mitsuhiro Shimada · Shin Watanabe · Shingo Tagami · Takuma Matsumoto · Yoshifumi R. Shimizu · Masanobu Yahiro
We perform simultaneous analysis of (1) matter radii, (2) $B (E 2; 0^{+} \to 2^{+})$ transition probabilities, and (3) excitation energies, $E (2^{+})$ and $E (4^{+})$ , for $^{24 - 40}$ Mg by using the beyond mean-field (BMF) framework with angular-momentum-projected configuration mixing with respect to the axially symmetric $β_{2}$ deformation with infinitesimal cranking. The BMF calculations successfully reproduce all of the data for $r_{m}$ , $B (E 2)$ , and $E (2^{+})$ and $E (4^{+})$ , indicating that it is quite useful for data analysis, particularly for low-lying states. We also discuss the absolute value of the deformation parameter $β_{2}$ deduced from measured values of $B (E 2)$ and $r_{m}$ . This framework makes it possible to investigate the effects of $β_{2}$ deformation, the change in $β_{2}$ due to restoration of rotational symmetry, $β_{2}$ configuration mixing, and the inclusion of time-odd components by infinitesimal cranking. Under the assumption of axial deformation and parity conservation, we clarify which effect is important for each of the three measurements, and propose the kinds of BMF calculations that are practical for each of the three kinds of observables.
Comments:
11 pages, 12 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1605.08585 [pdf]
PRC(2016)·9 citations
04
[Submitted on 27 May 2016]
Induced Hyperon-Nucleon-Nucleon Interactions and the Hyperon Puzzle
Roland Wirth🇩🇪 · Robert Roth🇩🇪
We present the first ab initio calculations for $p$ -shell hypernuclei including hyperon-nucleon-nucleon (YNN) contributions induced by a Similarity Renormalization Group transformation of the initial hyperon-nucleon interaction. The transformation including the YNN terms conserves the spectrum of the Hamiltonian while drastically improving model-space convergence of the Importance-Truncated No-Core Shell Model, allowing a precise extraction of binding and excitation energies. Results using a hyperon-nucleon interaction at leading order in chiral effective field theory for lower- to mid- $p$ -shell hypernuclei show a good reproduction of experimental excitation energies while hyperon binding energies are typically overestimated. The induced YNN contributions are strongly repulsive and we show that they are related to a decoupling of the $Σ$ hyperons from the hypernuclear system, i.e., a suppression of the $Λ$ - $Σ$ conversion terms in the Hamiltonian. This is linked to the so-called hyperon puzzle in neutron-star physics and provides a basic mechanism for the explanation of strong $Λ$ NN three-baryon forces.
Comments:
5 pages, 5 figures
Subjects:
Nuclear Theory (nucl-th); Solar and Stellar Astrophysics (astro-ph.SR); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1605.08677 [pdf]
PRL(2016)·53 citations
05
[Submitted on 27 May 2016]
Relativistic hydrodynamics in heavy-ion collisions: general aspects and recent developments
Amaresh Jaiswal🇩🇪 · Victor Roy🇩🇪
Relativistic hydrodynamics has been quite successful in explaining the collective behaviour of the QCD matter produced in high energy heavy-ion collisions at RHIC and LHC. We briefly review the latest developments in the hydrodynamical modeling of relativistic heavy-ion collisions. Essential ingredients of the model such as the hydrodynamic evolution equations, dissipation, initial conditions, equation of state, and freeze-out process are reviewed. We discuss observable quantities such as particle spectra and anisotropic flow and effect of viscosity on these observables. Recent developments such as event-by-event fluctuations, flow in small systems (proton-proton and proton-nucleus collisions), flow in ultra central collisions, longitudinal fluctuations and correlations and flow in intense magnetic field are also discussed.
Comments:
36 pages, 16 figures, invited review, published version
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1605.08694 [pdf]
Adv.High Energy Phys.(2016)·205 citations

Affiliations

first authorsco-authorsvia INSPIRE

Electric dipole response of neutron-rich Calcium isotopes in relativistic quasiparticle time blocking approximation

Spectroscopic factor strengths using ab initio approaches

Simultaneous analysis of matter radii, transition probabilities, and excitation energies of Mg isotopes by angular-momentum-projected configuration-mixing calculations

Induced Hyperon-Nucleon-Nucleon Interactions and the Hyperon Puzzle

Relativistic hydrodynamics in heavy-ion collisions: general aspects and recent developments

Affiliations

Spectroscopic factor strengths using $ab ini t i o$ approaches