Nuclear Theory·nucl-th

Monday·April 2, 2018

10 papers—7 primary·3 cross-listed

01
[Submitted on 30 Mar 2018]
Azimuthal angle distributions of neutrons emitted from the $^{9}$ Be( $γ$ , $n$ ) reaction with linearly polarized $γ$ -rays
Yuma Kikuchi · Kazuyuki Ogata · Takehito Hayakawa · Satoshi Chiba
The electromagnetic transitions of $^{9}$ Be with linearly polarized $γ$ -rays are calculated by using the $α$ ~+~ $α$ ~+~ $n$ three-body model and the complex-scaled solutions of the Lippmann-Schwinger equation; the azimuthal angle distributions of the emitted neutrons are investigated. We calculate the anisotropy parameter as a function of the photon incident energy $E_{γ}$ , and discuss how sensitive the anisotropy parameter is to nuclear structure and transition modes. The result suggests that the azimuthal angle distribution of neutrons emitted from the $^{9}$ Be( $γ$ , $n$ ) reaction with the linearly polarized $γ$ -rays is useful to identify the resonances in the final states even if it is not clearly observed in the cross section.
Comments:
13 pages, 3 figures, 1 table, to be submitted to PRC
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1803.11327 [pdf]
PRC(2018)·0 citations
02
[Submitted on 30 Mar 2018]
Resonance in the $Y_{c} N$ potential model
Saori Maeda🇯🇵 · Makoto Oka🇯🇵 · Yan-Rui Liu🇨🇳
We calculate two-body $J^{π} = 0^{+}, 1^{+}$ , and $J^{π} = 2^{+}$ resonance states of $Y_{c}$ ( $= Λ_{c}$ , $Σ_{c}$ , or $Σ_{c}^{*}$ ) and $N$ using the complex scaling method. We employ the $Y_{c} N$ -CTNN potentials, which were proposed in our previous study, and obtain four resonances near $Σ_{c} N$ and $Σ_{c}^{*} N$ thresholds. From the analysis by the binding energies of partial channel systems, we conclude that these resonance states are Feshbach resonances. We compare the results with the $Y_{c} N$ resonance states in the heavy quark limit, where the $Σ_{c} N$ and $Σ_{c}^{*} N$ thresholds are degenerate, and find that they form two pairs of the heavy-quark doublets in agreement with the heavy quark spin symmetry.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1803.11349 [pdf]
PRC(2018)·16 citations
03
[Submitted on 30 Mar 2018]
Quark model estimate of hidden-charm pentaquark resonances
Emiko Hiyama🇯🇵 · Atsushi Hosaka🇯🇵 · Makoto Oka🇯🇵 · Jean-March Richard🇫🇷
A quark model, which reproduces the ground-state mesons and baryons, i.e., the threshold energies, is applied to the $q q q c c ˉ$ configurations, where $q$ is a light quark and~ $c$ the charmed quark. In the calculation, several open channels are explicitly included such as $\Jpsi + N$ , $η_{c} + N$ , $Λ_{c} + D$ , etc. To distinguish genuine resonances and estimate their width, we employ Gaussian Expansion Method supplemented by the real scaling method (stabilization). No resonance is found at the energies of the $P_{c} (4380)$ and $P_{c} (4450)$ pentaquarks. On the other hand, there is a sharp resonant state at 4690\,MeV with $J = 1/ 2^{-}$ state and another one at 4920\,MeV with $J = 3/ 2^{-}$ state, which have a compact structure.
Comments:
9 pages, 9 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1803.11369 [pdf]
PRC(2018)·76 citations
04
[Submitted on 30 Mar 2018]
Ab initio predictions for polarized DT thermonuclear fusion
Guillaume Hupin🇫🇷 · Sofia Quaglioni🇺🇸 · Petr Navrátil🇨🇦
The fusion of deuterium (D) with tritium (T) is the most promising of the reactions that could power the thermonuclear reactors of the future. Already favored for its low activation energy and high yield, it may lead to even more efficient energy generation if obtained in a polarized state, i.e. with the spin of the reactants aligned. While the DT fusion rate has been measured extensively, very little is known of the effects of polarization. Meanwhile, arriving at a fundamental understanding of the fusion process in terms of the laws of quantum mechanics and the underlying theory of the strong force has been a daunting challenge. We use nuclear forces derived from chiral effective field theory and apply the ab initio reaction method known as no-core shell model with continuum to predict, for the first time from first principles, the enhancement factor of the polarized DT fusion rate and anisotropy of the emitted neutron and {\alpha} particle.
Subjects:
Nuclear Theory (nucl-th); Plasma Physics (physics.plasm-ph)
arXiv:
1803.11378 [pdf]
Nature Commun.(2019)·58 citations
05
[Submitted on 29 Mar 2018]
Estimates of the baryon densities attainable in heavy-ion collisions from the beam energy scan program
Yu. B. Ivanov🇷🇺 · A. A. Soldatov🇷🇺
The baryon and energy densities attained in fragmentation regions in central Au+Au collisions in the energy range of the Beam Energy Scan (BES) program at the Relativistic Heavy-Ion Collider (RHIC) are estimated within the model of the three-fluid dynamics. It is shown that a considerable part of the baryon charge is stopped in the central fireball. Even at 39 GeV, approximately 70% of the total baryon charge turns out to be stopped. The fraction of this stopped baryon charge decreases with collision energy rise, from 100% at 7.7 GeV to $\sim$ 40% at 62 GeV. The highest initial baryon densities of the thermalized matter, $n_{B} / n_{0} \approx$ 10, are reached in the central region of colliding nuclei at $s_{N N} =$ 20--40 GeV. These highest densities develop up to quite moderate freeze-out baryon densities at the midrapidity because the matter of the central fireball is pushed out to fragmentation regions by one-dimensional expansion. Therefore, consequences of these high initial baryon densities can be observed only in the fragmentation regions of colliding nuclei in AFTER@LHC experiments in the fixed-target mode.
Comments:
9 pages, 5 figures. The article is substantially revised. The version accepted in PRC
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1803.11474 [pdf]
PRC(2018)·10 citations
06
[Submitted on 29 Mar 2018]
Skyrme density functional description of the double magic $^{78}$ Ni nucleus
D. M. Brink · Fl. Stancu
We calculate the single particle spectrum of the double magic nucleus $^{78}$ Ni in a Hartree-Fock approach using the Skyrme density-dependent effective interaction containing central, spin-orbit and tensor parts. We show that the tensor part has an important effect on the spin-orbit splitting of the proton $1 f$ orbit which may explain the survival of magicity so far from the stability valley. We confirm the inversion of the $1 f 5/2$ and $2 p 3/2$ levels at the neutron number 48 in the Ni isotopic chain expected from previous Monte Carlo shell model calculations and supported by experimental observation.
Comments:
14 pages, 5 figures, typos corrected. arXiv admin note: text overlap with arXiv:nucl-th/0702065
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1803.11476 [pdf]
PRC(2018)·16 citations
07
[Submitted on 30 Mar 2018]
Extraction of Polarization Parameters in the $p ˉ p \to Ω ˉ Ω$ Reaction
Elisabetta Perotti
A method to extract the polarization of $Ω$ hyperons produced via the strong interaction is presented. Assuming they are spin 3/2 particles, the corresponding spin density matrix can be written in terms of seven non-zero polarization parameters, all retrievable from the angular distribution of the decay products. Moreover by considering the full decay chain $Ω \to Λ K \to p π K$ the magnitude of the asymmetry parameters $β_{Ω}$ and $γ_{Ω}$ can be obtained. This method, applied here to the specific $Ω$ case, can be generalized to any weakly decaying hyperon and is perfectly suited for the PANDA experiment where hyperon-antihyperon pairs will be copiously produced in proton-antiproton collisions. The aim is to take a step forward towards the understanding of the mechanism that reigns strangeness production in these processes.
Comments:
This contribution was written for the FAIRness 2017 workshop and will appear in the Open Access Journal of Physics: Conference Series (JPCS)
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1803.11482 [pdf]
J.Phys.Conf.Ser.(2018)·4 citations

Affiliations

first authorsco-authorsvia INSPIRE

Azimuthal angle distributions of neutrons emitted from the 9Be(γ,n) reaction with linearly polarized γ-rays

Resonance in the Yc​N potential model

Quark model estimate of hidden-charm pentaquark resonances

Ab initio predictions for polarized DT thermonuclear fusion

Estimates of the baryon densities attainable in heavy-ion collisions from the beam energy scan program

Skyrme density functional description of the double magic 78Ni nucleus

Extraction of Polarization Parameters in the pˉ​p→ΩˉΩ Reaction

Affiliations

Azimuthal angle distributions of neutrons emitted from the $^{9}$ Be( $γ$ , $n$ ) reaction with linearly polarized $γ$ -rays

Resonance in the $Y_{c} N$ potential model

Skyrme density functional description of the double magic $^{78}$ Ni nucleus

Extraction of Polarization Parameters in the $p ˉ p \to Ω ˉ Ω$ Reaction