Nuclear Theory·nucl-th

Tuesday·August 14, 2018

13 papers—8 primary·5 cross-listed

01
Variational Principle Directly on the Coherent Pair Condensate. I. the BCS Case
L. Y. Jia🇨🇳
We propose a scheme to perform the variational principle directly on the coherent pair condensate (VDPC). The result is equivalent to that of the so-called variation after particle-number projection, but now the particle number is always conserved and the time-consuming projection is avoided. This work considers VDPC+BCS. We derive analytical expressions for the average energy and its gradient in terms of the coherent pair structure. In addition, we give analytically the pair structure at the energy minimum, and discuss its asymptotic behavior away from the Fermi surface, which looks quite simple and allows easy physical interpretations. The new algorithm iterates these pair-structure expressions to minimize energy. We demonstrate the new algorithm in a semi-realistic example using the realistic $V_{l o w - k}$ interaction and large model spaces (up to 15 harmonic-oscillator major shells). The energy can be minimized to practically arbitrary precision. The result shows that the realistic $V_{l o w - k}$ interaction does not cause divergences in the pairing channel, although tiny occupation numbers (for example smaller than $1 0^{- 5}$ ) contribute to the energy (by a few tens of keV). We also give analytical expressions for the gradient of energy with respect to changes of the canonical single-particle basis, which will be necessary for the next work in this series: VDPC+HFB.
nucl-thPRC(2019)·8 citations
02
On the peripheral-tube description of the two-particle correlations in nuclear collisions
Dan Wen🇧🇷 · Wagner M. Castilho🇧🇷 · Kai Lin🇧🇷 · Wei-Liang Qian🇧🇷 · Yogiro Hama🇧🇷 · Takeshi Kodama🇧🇷
In this work, we study the two-particle correlations regarding a peripheral tube model. From our perspective, the main characteristics of the observed two-particle correlations are attributed to the multiplicity fluctuations and the locally disturbed one-particle distribution associated with hydrodynamic response to the geometric fluctuations in the initial conditions. We investigate the properties of the initial conditions and collective flow concerning the proposed model. It is shown that the experimental data can be reproduced by hydrodynamical simulations using appropriately constructed initial conditions. Besides, instead of numerical calibration, we extract the model parameters according to their respective physical interpretations and show that the obtained numerical values are indeed qualitatively in agreement with the observed data. Possible implications of the present approach are discussed.
nucl-thJ.Phys.G(2019)·9 citations
03
Explore nuclear multiple chirality in $A \sim 60$ mass region within covariant density functional theory
J. Peng · Q. B. Chen
The nuclear multiple chirality in $A \sim 60$ mass region is explored by the adiabatic and configuration-fixed constrained covariant density functional theory for cobalt isotopes. The potential-energy curves and triaxiality parameters $γ$ as functions of the deformation parameter $β$ in $^{54, 56, 57, 58, 59, 60}$ Co are obtained. It is found that there are high- $j$ particle(s) and hole(s) configurations with prominent triaxially deformed shapes in these isotopes. This points towards that the existence of chirality or multiple chirality in $A \sim 60$ mass region are highly anticipated.
nucl-thnucl-exPRC(2018)·21 citations
04
Insight into nuclear midshell structures by study of $K$ -isomers in rare-earth neutron-rich nuclei
Xiao-Tao He · Yu-Chun Li
Inspired by the newly discovered isomeric states in the rare-earth neutron-rich nuclei, high- $K$ isomeric states in neutron-rich samarium and gadolinium isotopes are investigated within the framework of the cranked shell model (CSM) with pairing correlation treated by a particle-number-conserving (PNC) method. The experimental multi-particle state energies and moments of inertia are reproduced quite well by the PNC-CSM calculations. A remarkable effect from the high-order deformation $ε_{6}$ is demonstrated. Based on the occupation probabilities, the configurations are assigned to the observed high- $K$ isomeric states. The lower $5^{-}$ isomeric state in $^{158}$ Sm is preferred as the two-proton state with configuration $π \frac{5}{2}^{+} [413] \otimes π \frac{5}{2}^{-} [532]$ . More low-lying two-particle states are predicted. The systematics of the electronic quadrupole transition probabilities, $B (E 2)$ values along the neodymium, samarium, gadolinium and dysprosium isotopes and $N = 96, 98, 100, 102$ isotones chains is investigated to reveal the midshell collectivities.
nucl-thnucl-exPRC(2018)·17 citations
05
Relativistic Mean-Field and Beyond Approaches for Deformed Hypernuclei
J. M. Yao · H. Mei · K. Hagino · T. Motoba
We report the recent progress in relativistic mean-field (RMF) and beyond approaches for the low-energy structure of deformed hypernuclei. We show that the $Λ$ hyperon with orbital angular momentum $ℓ = 0$ (or $ℓ > 1$ ) generally reduces (enhances) nuclear quadrupole collectivity. The beyond mean-field studies of hypernuclear low-lying states demonstrate that there is generally a large configuration mixing between the two components $[^{A - 1} Z (I^{+}) \otimes Λ p_{1/2}]^{J}$ and $[^{A - 1} Z (I \pm 2^{+}) \otimes Λ p_{3/2}]^{J}$ in the hypernuclear $1/ 2_{1}^{-}, 3/ 2_{1}^{-}$ states. The mixing weight increases as the collective correlation of nuclear core becomes stronger. Finally, we show how the energies of hypernuclear low-lying states are sensitive to parameters in the effective $N Λ$ interaction, the uncertainty of which has a large impact on the predicted maximal mass of neutron stars.
nucl-thAIP Conf.Proc.(2019)·2 citations
06
Extracting strange quark freeze-out information in Pb+Pb collisions at $s_{N N}$ =2.76 TeV from $ϕ$ and $Ω$ production
Jie Pu🇨🇳 · Kai-Jia Sun🇨🇳 · Lie-Wen Chen🇨🇳
Using a covariant quark coalescence model combined with a blast-wave-like analytical parametrization for (anti-)strange quark phase-space freeze-out configuration, we extract information on strange quark freeze-out dynamics in Pb+Pb collisions at $s_{N N}$ =2.76 TeV by fitting the measured transverse momentum spectra and elliptic flows ( $v_{2}$ ) of $ϕ$ mesons and $Ω$ baryons. We find that although both the measured and calculated $v_{2}$ of $ϕ$ and $Ω$ satisfy the number-of-constituent-quark (NCQ) scaling, the NCQ-scaled $v_{2}$ is significantly smaller than the $v_{2}$ of strange quarks, implying that the NCQ-scaled $v_{2}$ of $ϕ$ and $Ω$ cannot be simply identified as the $v_{2}$ of strange quarks at hadronization. Meanwhile, our results indicate that the covariant quark coalescence model can nicely describe the spectra and elliptic flows of $ϕ$ and $Ω$ simultaneously, suggesting the coalescence mechanism is still valid for $ϕ$ and $Ω$ production in Pb+Pb collisions at LHC energies.
nucl-thhep-phnucl-exPRC(2018)·5 citations
07
Theoretical study of the direct $α + d$ $\to$ $^{6}$ Li + $γ$ astrophysical capture process in a three-body model II. Reaction rates and primordial abundance
E.M. Tursunov · S.A. Turakulov · A.S. Kadyrov · I. Bray
The astrophysical S-factor and reaction rate of the direct capture process $α + d$ $\to$ $^{6}$ Li + $γ$ , as well as the abundance of the $^{6}$ Li element are estimated in a three-body model. The initial state is factorized into the deuteron bound state and the $α + d$ scattering state. The final nucleus $^{6}$ Li(1+) is described as a three-body bound state $α + n + p$ in the hyperspherical Lagrange-mesh method. Corrections to the asymptotics of the overlap integral in the S- and D-waves have been done for the E2 S-factor. The isospin forbidden E1 S-factor is calculated from the initial isosinglet states to the small isotriplet components of the final $^{6}$ Li(1+) bound state. It is shown that the three-body model is able to reproduce the newest experimental data of the LUNA collaboration for the astrophysical S-factor and the reaction rates within the experimental error bars. The estimated $^{6}$ Li/H abundance ratio of $(0.67 \pm 0.01) \times 1 0^{- 14}$ is in a very good agreement with the recent measurement $(0.80 \pm 0.18) \times 1 0^{- 14}$ of the LUNA collaboration.
nucl-thastro-ph.COastro-ph.GAastro-ph.SRPRC(2018)·23 citations
08
Angle and magnitude decorrelation in the factorization breaking of collective flow
Piotr Bozek🇵🇱
The collective harmonic flow in heavy-ion collisions correlates particles at all transverse momenta to be emitted preferably some directions. The factorization breaking coefficient measures the small decorrelation of the flow harmonics at two different transverse momenta. Using the hydrodynamic model I study in details the decorrelation of the harmonic flow due to the flow angle and the flow magnitude decorrelation at two transverse momenta. The effect can be seen in experiment measuring factorization breaking coefficients for the square of the harmonic flow vector at two transverse momenta. The hydrodynamic model predicts that the decorrelation of the flow magnitudes is about one half of the decorrelation of the overall flow (combining flow angle and flow magnitude decorrelations). These results are consistent with the principal component analysis of correlators of flow vectors squared.
nucl-thhep-exnucl-exPRC(2018)·18 citations

Affiliations

first authorsco-authorsvia INSPIRE