Nuclear Theory·nucl-th

Monday·April 2, 2018

10 papers—7 primary·3 cross-listed

01
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.
nucl-thPRC(2018)·0 citations
02
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.
nucl-thPRC(2018)·16 citations
03
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.
nucl-thPRC(2018)·76 citations
04
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.
nucl-thphysics.plasm-phNature Commun.(2019)·58 citations
05
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.
nucl-thhep-phPRC(2018)·10 citations
06
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.
nucl-thPRC(2018)·16 citations
07
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.
nucl-thJ.Phys.Conf.Ser.(2018)·4 citations
08
Effective-range corrections to the ground-state energy of the weakly-interacting Bose gas in two dimensions
Silas R. Beane
Nonuniversal effects due to leading effective-range corrections are computed for the ground-state energy of the weakly-coupled repulsive Bose gas in two spatial dimensions. Using an effective field theory of contact interactions, these corrections are computed first by considering fluctuations around the mean-field free energy of a system of interacting bosons. This result is then confirmed by an exact calculation in which the energy of a finite number of bosons interacting in a square with period boundary conditions is computed and the thermodynamic limit is explicitly taken.
↳ cond-mat.quant-gasnucl-thEur.Phys.J.D(2018)·6 citations
09
Semileptonic decay of $B_{c}^{-}$ into $X (3930)$ , $X (3940)$ , $X (4160)$
Natsumi Ikeno🇯🇵 · Melahat Bayar🇹🇷 · Eulogio Oset🇪🇸
We study the semileptonic decay of $B_{c}^{-}$ meson into $ν ˉ l^{-}$ and the isospin zero $X (3930) (2^{++})$ , $X (3940) (0^{++})$ , $X (4160) (2^{++})$ resonances. We look at the reaction from the perspective that these resonaces appear as dynamically generated from the vector-vector interaction in the charm sector, and couple strongly to $D^{*} D^{*} ˉ$ and $D_{s}^{*} D_{s}^{*} ˉ$ . We also look into the $B_{c}^{-} \to ν ˉ_{l} l^{-} D^{*} D^{*} ˉ$ and $B_{c}^{-} \to ν ˉ_{l} l^{-} D_{s}^{*} D_{s}^{*} ˉ$ reactions close to threshold and relate the $D^{*} D^{*} ˉ$ and $D_{s}^{*} D_{s}^{*} ˉ$ mass distribution to the rate of production of the $X$ resonances.
↳ hep-phnucl-thEPJC(2018)·5 citations
10
Radiative transitions between $0^{-+}$ and $1^{--}$ heavy quarkonia on the light front
Meijian Li🇺🇸 · Yang Li🇺🇸 · Pieter Maris🇺🇸 · James P. Vary🇺🇸
We present calculations of radiative transitions between vector and pseudoscalar quarkonia in the light-front Hamiltonian approach. The valence sector light-front wavefunctions of heavy quarkonia are obtained from the Basis Light-Front Quantization (BLFQ) approach in a holographic basis. We study the transition form factor with both the traditional "good current" $J^{+}$ and the transverse current $J_{⊥}$ (in particular, $J^{R} = J^{x} + i J^{y}$ ). This allows us to investigate the role of rotational symmetry by considering vector mesons with different magnetic projections ( $m_{j} = 0, \pm 1$ ). We use the $m_{j} = 0$ state of the vector meson to obtain the transition form factor, since this procedure employs the dominant spin components of the light-front wavefunctions and is more robust in practical calculations. While the $m_{j} = \pm 1$ states are also examined, transition form factors depend on subdominant components of the light-front wavefunctions and are less robust. Transitions between states below the open-flavor thresholds are computed, including those for excited states. Comparisons are made with the experimental measurements as well as with Lattice QCD and quark model results. In addition, we apply the transverse current to calculate the decay constant of vector mesons where we obtain consistent results using either $m_{j} = 0$ or $m_{j} = 1$ light-front wavefunctions. This consistency provides evidence for features of rotational symmetry within the model.
↳ hep-phnucl-thPRD(2018)·47 citations

Affiliations

first authorsco-authorsvia INSPIRE