Nuclear Theory·nucl-th

Tuesday·August 14, 2018

13 papers—8 primary·5 cross-listed

01
[Submitted on 11 Aug 2018]
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.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1808.03729 [pdf]
PRC(2019)·8 citations
02
[Submitted on 11 Aug 2018]
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.
Comments:
11 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1808.03775 [pdf]
J.Phys.G(2019)·9 citations
03
[Submitted on 11 Aug 2018]
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.
Comments:
13 pages, 5 figures, 1 table, accepted by Phys. Rev. C
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1808.03776 [pdf]
PRC(2018)·21 citations
04
[Submitted on 12 Aug 2018]
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.
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1808.03945 [pdf]
PRC(2018)·17 citations
05
[Submitted on 13 Aug 2018]
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.
Comments:
12 pages, 7 figures. A plenary talk given at the 13th International Conference on Hypernuclear and Strange Particle Physics, June 24-29, 2018, Portsmouth, VA
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1808.04042 [pdf]
AIP Conf.Proc.(2019)·2 citations
06
[Submitted on 13 Aug 2018]
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.
Comments:
7 pages, 3 figures, 1 table. Some results updated and discussions added. Accepted version to appear in PRC
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1808.04053 [pdf]
PRC(2018)·5 citations
07
[Submitted on 13 Aug 2018]
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.
Comments:
8 pages, 2 tables and 6 figures
Subjects:
Nuclear Theory (nucl-th); Cosmology and Nongalactic Astrophysics (astro-ph.CO); Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)
arXiv:
1808.04125 [pdf]
PRC(2018)·23 citations
08
[Submitted on 13 Aug 2018]
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.
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex)
arXiv:
1808.04248 [pdf]
PRC(2018)·18 citations
09
[Submitted on 2 Aug 2018] (cross-list from hep-th)
M-Theory Exotic Scalar Glueball Decays to Mesons at Finite Coupling
Vikas Yadav🇮🇳 · Aalok Misra🇮🇳
Using the pull-back of the perturbed type IIA metric corresponding to the perturbation of arXiv:hep-th/1306.4339's M-theory uplift of arXiv:hep-th/0902.1540's UV-complete top-down type IIB holographic dual of large- $N$ thermal QCD, at finite coupling, we obtain the interaction Lagrangian corresponding to exotic scalar glueball( $G_{E}$ )- $ρ / π$ -meson interaction, linear in the exotic scalar glueball and up to quartic order in the $π$ mesons. In the Lagrangian, the coupling constants are determined as (radial integrals of) arXiv:hep-th/1306.4339's M-theory uplift's metric components and six radial functions appearing in the M-theory metric perturbations. Assuming $M_{G} > 2 M_{ρ}$ , we then compute $ρ \to 2 π, G_{E} \to 2 π, 2 ρ, ρ + 2 π$ decay widths as well as the direct and indirect (mediated via $ρ$ mesons) $G_{E} \to 4 π$ decays. For numerics, we choose $f 0 [1710]$ and compare with previous calculations. We emphasize that our results can be made to match PDG data (and improvements thereof) exactly by appropriate tuning of some constants of integration appearing in the solution of the M-theory metric perturbations and the $ρ$ and $π$ meson radial profile functions - a flexibility that our calculations permits.
Comments:
v3:49 pages, LaTeX, 2 Figures, accepted journal (JHEP) version
Subjects:
High Energy Physics — Theory (hep-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1808.01182 [pdf]
JHEP(2018)·15 citations
10
[Submitted on 10 Aug 2018] (cross-list from hep-ph)
Novel tools and observables for jet physics in heavy-ion collisions
Harry Arthur Andrews🇬🇧 · Liliana Apolinario🇨🇭 · Redmer Alexander Bertens🇵🇹 · Christian Bierlich🇺🇸 · Matteo Cacciari🇸🇪 · Yi Chen🇫🇷 · Yang-Ting Chien🇨🇭 · Leticia Cunqueiro Mendez🇺🇸 · Michal Deak🇺🇸 · David d'Enterria🇵🇱 · Fabio Dominguez🇪🇸 · Philip Coleman Harris🇺🇸 and 16 other authors
Studies of fully-reconstructed jets in heavy-ion collisions aim at extracting thermodynamical and transport properties of hot and dense QCD matter. Recently, a plethora of new jet substructure observables have been theoretically and experimentally developed that provide novel precise insights on the modifications of the parton radiation pattern induced by a QCD medium. This report, summarizing the main lines of discussion at the 5th Heavy Ion Jet Workshop and CERN TH institute "Novel tools and observables for jet physics in heavy-ion collisions" in 2017, presents a first attempt at outlining a strategy for isolating and identifying the relevant physical processes that are responsible for the observed medium-induced jet modifications. These studies combine theory insights, based on the Lund parton splitting map, with sophisticated jet reconstruction techniques, including grooming and background subtraction algorithms.
Comments:
25 pages, report from the CERN TH institute "Novel tools and observables for jet physics in heavy-ion collisions", version accepted for publication in J. Phys. G
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1808.03689 [pdf]
J.Phys.G(2020)·133 citations
11
[Submitted on 10 Aug 2018] (cross-list from hep-ph)
Equation of state for QCD with a critical point from the 3D Ising Model
Paolo Parotto🇺🇸
Current knowledge of the finite-density QCD equation of state from first principles is limited to a Taylor expansion in the baryonic chemical potential around $μ_{B} = 0$ . By means of a scaling form for the equation of state of the 3D Ising model and a non-universal, parametrized map to QCD coordinates, we construct a family of equations of state matching state of the art first principle Lattice QCD calculations and including the correct critical behavior, which can be readily employed in hydrodynamical simulations of heavy ion collisions at finite density, covering most of the BES range at RHIC. This contribution reports on work done within the Fluctuations/Equation of State working group of the BEST Collaboration.
Comments:
3 pages, 1 figure, Quark Matter 2018 conference proceeding
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1808.03695 [pdf]
NPA(2019)·4 citations
12
[Submitted on 13 Aug 2018] (cross-list from hep-ph)
Strange matter and kaon to pion ratio in SU(3) PNJL model
A. V. Friesen🇷🇺 · Yu. L. Kalinovsky🇷🇺 · V. D. Toneev🇷🇺
The behavior of strange matter in the frame of the SU(3)Polyakov-loop extended Nambu-Jona-Lasinio model including $U_{A} (1)$ anomaly is considered. We discuss the appearance of a peak in the ratio of the number of strange mesons to non-strange mesons known as the "horn". The PNJL model gives a schematic description of the chiral phase transition and meson properties at finite temperature and density. Using the model, we can show that the splitting of kaon and anti-kaon masses appears as a result of introduction of density. This may explain the difference in the $K^{+} / π^{+}$ ratio and $K^{-} / π^{-}$ ratio at low $s_{N N}$ and their tendency to the same value at high $s_{N N}$ . We also show that the rise in the ratio $K^{+} / π^{+}$ appears near CEP when we build the $K^{+} / π^{+}$ ratio along the phase transition diagram and it can be considered as a critical region signal.
Comments:
7 pages, 7 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1808.04179 [pdf]
PRC(2019)·11 citations
13
[Submitted on 13 Aug 2018] (cross-list from hep-ph)
Lowest-order electron-electron and electron-muon scattering in a strong magnetic field
Abhishek Tiwari🇮🇳 · Binoy Krishna Patra🇮🇳
In this work we have investigated how the much studied scattering processes in vacuum at the lowest-order, {\em viz.} electron-muon ( $e$ - $μ$ ) scattering in both $s$ - and $t$ -channel, Bhabha scattering, and Møller scattering, have been modified in the presence of a strong magnetic field ( $∣ e B ∣ >> m^{2}$ , $m$ is the mass of electron or muon). For that purpose, we have first calculated the square of the matrix element by summing over the spin states, using the spinors in the presence of a strong magnetic field and then obtain the crosssection by integrating over the available phase space for the final states and averaging over the initial states. The first noticeable observation in the spin-summed of the matrix element squared is that the interference term between $s$ - and $t$ -channel and $t$ - and $u$ -channel in Bhabha and Møller scattering, respectively are missing in the presence of strong magnetic field. We have found that in the presence of strong magnetic field, the crosssection of $e^{-} e^{+} \to μ^{-} μ^{+}$ annihilation process in the lowest order decreases inversely proportional to the fourth power of the center-of-mass energy ( $s$ ), compared to the inversely proportional to the square of center-of-mass energy in vacuum alone. Like in vacuum, the crosssection for $e$ - $μ$ scattering in $t$ channel, {\em i.e.} for $e^{-} μ^{-} \to e^{-} μ^{-}$ process, even in a strong magnetic field too diverges but the finite part decreases with $s$ much faster than in vacuum alone. Similarly the crosssections for both Bhabha and Møller scattering at the lowest-order diverges in the infrared limit. However, the finite term decreases with $s$ much faster than the vacuum alone. In addition there is finite negative contribution, which is independent of $s$ and decreases with the magnetic field.
Comments:
41 pages with 10 figures/diagrams
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1808.04236 [pdf]
6 citations

Affiliations

first authorsco-authorsvia INSPIRE