Nuclear Theory·nucl-th

Tuesday·September 5, 2017

13 papers—5 primary·8 cross-listed

01
[Submitted on 3 Sept 2017]
High-momentum antisymmetrized molecular dynamics compared with tensor-optimized shell model for strong tensor correlation
Takayuki Myo · Hiroshi Toki · Kiyomi Ikeda · Hisashi Horiuchi · Tadahiro Suhara · Mengjiao Lyu · Masahiro Isaka · Taiichi Yamada
We treat the tensor correlation in antisymmetrized molecular dynamics (AMD) including large-relative-momentum components among nucleon pairs for finite nuclei. The tensor correlation is described by using large imaginary centroid vectors of Gaussian wave packets for nucleon pairs with opposite directions, which makes a large relative momentum. We superpose the AMD basis states, in which one nucleon pair has various relative momenta for all directions; this new method is called "high-momentum AMD" (HM-AMD). We show the results for $^{4}$ He using the effective interaction having a strong tensor force. It is found that HM-AMD provides a large tensor matrix element comparable to the case of the tensor-optimized shell model (TOSM), in which the two-particle-two-hole (2p-2h) excitations are fully included to describe the tensor correlation. The results of two methods agree with each other at the level of the Hamiltonian components of $^{4}$ He. This indicates that in HM-AMD the high-momentum components described by the imaginary centroid vectors of the nucleon pair provide the equivalent effect of the 2p-2h excitations for the tensor correlation.
Comments:
11 pages, 4 figures, added references
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1709.00660 [pdf]
PTEP(2017)·25 citations
02
[Submitted on 4 Sept 2017]
Global analysis of Skyrme forces with higher-order density dependence
Z.W. Zuo · J.C. Pei · X.Y. Xiong · Y. Zhu
The density dependent term in Skyrme forces is essential, which simulates three-body and many-body correlations beyond the low-momentum two-body interaction. We speculate that a single density term may be insufficient and a higher-order density dependent term is added. The present work investigates the influences of higher-order density dependencies based on extended UNEDF0 and SkM* forces. The global descriptions of nuclear masses and charge radii have been presented. Consequently the extended UNEDF0 force gives a global rms error on binding energies of 1.29 MeV. The influences on fission barriers and equation of state have also been investigated. The perspectives to improve Skyrme forces have also been discussed, including global center-of-mass corrections and Lipkin-Nogami pairing corrections.
Comments:
8 pages, 9 figures, to be published in Chin.Phys.C
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1709.00802 [pdf]
CPC(2018)·11 citations
03
[Submitted on 4 Sept 2017]
Higher order net-proton number cumulants dependence on the centrality definition and other spurious effects
S. Sombun🇹🇭 · J. Steinheimer🇩🇪 · C. Herold🇹🇭 · A. Limphirat🇹🇭 · Y. Yan🇹🇭 · M. Bleicher🇩🇪
We study the dependence of the normalized moments of the net-proton multiplicity distributions on the definition of centrality in relativistic nuclear collisions at a beam energy of $s_{NN} = 7.7$ GeV. Using the UrQMD model as event generator we find that the centrality definition has a large effect on the extracted cumulant ratios. Furthermore we find that the finite efficiency for the determination of the centrality introduces an additional systematic uncertainty. Finally, we quantitatively investigate the effects of event-pile up and other possible spurious effects which may change the measured proton number. We find that pile-up alone is not sufficient to describe the data and show that a random double counting of events, adding significantly to the measured proton number, affects mainly the higher order cumulants in most central collisions.
Comments:
10 pages 13 figures, version accepted by JPG
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1709.00879 [pdf]
J.Phys.G(2018)·19 citations
04
[Submitted on 4 Sept 2017]
Many-body forces in magnetic neutron stars
R.O. Gomes · B. Franzon · V. Dexheimer · S. Schramm
In this work, we study in detail the effects of many-body forces on the equation of state and the structure of magnetic neutron stars. The stellar matter is described within a relativistic mean field formalism that takes into account many-body forces by means of a non-linear meson field dependence on the nuclear interaction coupling constants. We assume that matter is at zero temperature, charge neutral, in beta-equilibrium, and populated by the baryon octet, electrons, and muons. In order to study the effects of different degrees of stiffness in the equation of state, we explore the parameter space of the model, which reproduces nuclear matter properties at saturation, as well as massive neutron stars. Magnetic field effects are introduced both in the equation of state and in the macroscopic structure of stars by the self-consistent solution of the Einstein-Maxwell equations. In addition, effects of poloidal magnetic fields on the global properties of stars, as well as density and magnetic field profiles are investigated. We find that not only different macroscopic magnetic field distributions, but also different parameterizations of the model for a fixed magnetic field distribution impact the gravitational mass, deformation and internal density profiles of stars. Finally, we also show that strong magnetic fields affect significantly the particle populations of stars
Comments:
accepted by The Astrophysical Journal
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1709.01017 [pdf]
ApJ(2017)·33 citations
05
[Submitted on 4 Sept 2017]
Collective excitations of a hot anisotropic QCD medium with Bhatnagar-Gross-Krook collisional kernel within an effective description
Avdhesh Kumar🇮🇳 · M. Yousuf Jamal🇮🇳 · Vinod Chandra🇮🇳 · Jitesh R. Bhatt🇮🇳
Collective modes of an anisotropic hot QCD medium have been studied within the semi-classical transport theory employing Bhatnagar-Gross-Krook (BGK) collisional kernel. The modeling of the isotropic medium is primarily based on a recent quasi-particle description of hot QCD equation of state where the medium effects have been encoded in effective gluon and quark/anti-quark momentum distributions that posses non-trivial energy dispersions. The anisotropic distribution functions are obtained in a straightforward the way by stretching or squeezing the isotropic ones along one of the directions. The gluon self-energy is computed using these distribution functions in a linearized transport equation with Bhatnagar-Gross-Krook (BGK) collisional kernel. Further, the tensor decomposition of gluon self-energy leads to the structure functions which eventually controls the dispersion relations and the collective mode structure of the medium. It has been seen that both the medium effects and collisions induce appreciable modifications to the collective modes and plasma excitations in the hot QCD medium.
Comments:
16 pages, 20 figures, two column
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1709.01032 [pdf]
PRD(2018)·34 citations
06
[Submitted on 1 Sept 2017] (cross-list from hep-ph)
Center phase transition from matter propagators in (scalar) QCD
M. Mitter🇦🇹 · M. Hopfer🇦🇹 · B.-J. Schaefer🇩🇪 · R. Alkofer🇦🇹
Novel order parameters for the confinement-deconfinement phase transition of quenched QCD and fundamentally charged scalar QCD are presented. Similar to the well-known dual condensate, they are defined via generalized matter propagators with $U (1)$ -valued boundary conditions. The order parameters are easily accessible with functional methods. Their validity and accessibility is explicitly demonstrated by numerical studies of the Dyson-Schwinger equations for the matter propagators. Even in the case of heavy scalar matter, where the propagator does not show a signature of the phase transition, a discontinuity due to the transition can be extracted in the order parameters, establishing also fundamentally charged scalar matter as a probe for color confinement.
Comments:
accepted version
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
1709.00299 [pdf]
PLB(2018)·5 citations
07
[Submitted on 2 Sept 2017] (cross-list from physics.atom-ph)
Isotope shift, non-linearity of King plots and the search for new particles
V. V. Flambaum🇩🇪 · A. J. Geddes🇦🇺 · A. V. Viatkina🇩🇪
We derive a mean-field relativistic formula for the isotope shift of an electronic energy level for arbitrary angular momentum; we then use it to predict the spectra of superheavy metastable neutron-rich isotopes belonging to the hypothetical island of stability. Our results may be applied to the search for superheavy atoms in astrophysical spectra using the known values of the transition frequencies for the neutron deficient isotopes produced in the laboratory. An example of a relevant astrophysical system may be the spectra of the Przybylski's star where superheavy elements up to Z=99 have been possibly identified. In addition, it has been recently suggested to use the measurements of King plot non-linearity in a search for hypothetical new light bosons. On the other hand, one can find the non-linear corrections to the King-plot arising already in the Standard Model framework. We investigate contributions to the non-linearity arising from relativistic effects in the isotope field-shift, the nuclear polarizability and many-body effects. It is found that the nuclear polarizability contribution can lead to the significant deviation of the King plot from linearity. Therefore, the measurements of the non-linearity of King plots may be applied to obtain the nuclear polarizability change between individual isotopes. We then proceed with providing a rough analytical estimate of the non-linearity arising solely from the effect of a hypothetical scalar boson. Our predictions give theoretical limitations on the sensitivity of the search for new interactions and should help to identify the most suitable atoms for corresponding experiments.
Subjects:
Atomic Physics (physics.atom-ph); Solar and Stellar Astrophysics (astro-ph.SR); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1709.00600 [pdf]
PRA(2018)·99 citations
08
[Submitted on 3 Sept 2017] (cross-list from hep-lat)
Most Strange Dibaryon from Lattice QCD
Shinya Gongyo🇯🇵 · Kenji Sasaki🇯🇵 · Sinya Aoki🇯🇵 · Takumi Doi🇯🇵 · Tetsuo Hatsuda🇯🇵 · Yoichi Ikeda🇯🇵 · Takashi Inoue🇯🇵 · Takumi Iritani🇯🇵 · Noriyoshi Ishii🇯🇵 · Takaya Miyamoto🇯🇵 · Hidekatsu Nemura🇯🇵
The $ΩΩ$ system in the $^{1} S_{0}$ channel (the most strange dibaryon) is studied on the basis of the (2+1)-flavor lattice QCD simulations with a large volume (8.1 fm) $^{3}$ and nearly physical pion mass $m_{π} ≃ 146$ MeV at a lattice spacing $a ≃ 0.0846$ fm. We show that lattice QCD data analysis by the HAL QCD method leads to the scattering length $a_{0} = 4.6 (6) (_{- 0.5}^{+ 1.2}) fm$ , the effective range $r_{eff} = 1.27 (3) (_{- 0.03}^{+ 0.06}) fm$ and the binding energy $B_{ΩΩ} = 1.6 (6) (_{- 0.6}^{+ 0.7}) MeV$ . These results indicate that the $ΩΩ$ system has an overall attraction and is located near the unitary regime. Such a system can be best searched experimentally by the pair-momentum correlation in relativistic heavy-ion collisions.
Comments:
6 pages and 4 figures
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1709.00654 [pdf]
PRL(2018)·154 citations
09
[Submitted on 3 Sept 2017] (cross-list from astro-ph.SR)
Abundance Uncertainties Obtained With the PizBuin Framework For Monte Carlo Reaction Rate Variations
T. Rauscher · N. Nishimura · G. Cescutti · R. Hirschi · A. St.J. Murphy
Uncertainties in nucleosynthesis models originating from uncertainties in astrophysical reaction rates were estimated in a Monte Carlo variation procedure. Thousands of rates were simultaneously varied within individual, temperature-dependent errors to calculate their combined effect on final abundances. After a presentation of the method, results from application to three different nucleosynthesis processes are shown: the $γ$ -process and the s-process in massive stars, and the main s-process in AGB stars (preliminary results). Thermal excitation of nuclei in the stellar plasma and the combined action of several reactions increase the final uncertainties above the level of the experimental errors. The total uncertainty, on the other hand, remains within a factor of two even in processes involving a large number of unmeasured rates, with some notable exceptions for nuclides whose production is spread over several stellar layers and for s-process branchings.
Comments:
8 pages, 4 figures; Proceedings of OMEG 2017, Daejeon, Korea, June 27-30, 2017; to appear in AIP Conf. Proc
Subjects:
Solar and Stellar Astrophysics (astro-ph.SR); High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1709.00690 [pdf]
AIP Conf.Proc.(2018)·2 citations
10
[Submitted on 3 Sept 2017] (cross-list from cond-mat.quant-gas)
Efimov states near a Feshbach resonance and the limits of van der Waals universality at finite background scattering length
Christian Langmack · Richard Schmidt · Wilhelm Zwerger
We calculate the spectrum of three-body Efimov bound states near a Feshbach resonance within a model which accounts both for the finite range of interactions and the presence of background scattering. The latter may be due to direct interactions in an open channel or a second overlapping Feshbach resonance. It is found that background scattering gives rise to substantial changes in the trimer spectrum as a function of the detuning away from a Feshbach resonance, in particular in the regime where the background channel supports Efimov states on its own. Compared to the situation with negligible background scattering, the regime where van der Waals universality applies is shifted to larger values of the resonance strength if the background scattering length is positive. For negative background scattering lengths, in turn, van der Waals universality extends to even small values of the resonance strength parameter, consistent with experimental results on Efimov states in $^{39}$ K. Within a simple model, we show that short-range three-body forces do not affect van der Waals universality significantly. Repulsive three-body forces may, however, explain the observed variation between around $- 8$ and $- 10$ of the ratio between the scattering length where the first Efimov trimer appears and the van der Waals length.
Comments:
17 pages, 13 figures; final version as published
Subjects:
Quantum Gases (cond-mat.quant-gas); Nuclear Theory (nucl-th); Quantum Physics (quant-ph)
arXiv:
1709.00749 [pdf]
PRA(2018)·14 citations
11
[Submitted on 3 Sept 2017] (cross-list from nucl-ex)
Collision Energy Dependence of Moments of Net-Kaon Multiplicity Distributions at RHIC
STAR Collaboration: L. Adamczyk · J. R. Adams · J. K. Adkins · G. Agakishiev · M. M. Aggarwal · Z. Ahammed · N. N. Ajitanand · I. Alekseev · D. M. Anderson · R. Aoyama · A. Aparin · D. Arkhipkin and 339 other authors
Fluctuations of conserved quantities such as baryon number, charge, and strangeness are sensitive to the correlation length of the hot and dense matter created in relativistic heavy-ion collisions and can be used to search for the QCD critical point. We report the first measurements of the moments of net-kaon multiplicity distributions in Au+Au collisions at $s_{NN}$ = 7.7, 11.5, 14.5, 19.6, 27, 39, 62.4, and 200 GeV. The collision centrality and energy dependence of the mean ( $M$ ), variance ( $σ^{2}$ ), skewness ( $S$ ), and kurtosis ( $κ$ ) for net-kaon multiplicity distributions as well as the ratio $σ^{2} / M$ and the products $S σ$ and $κ σ^{2}$ are presented. Comparisons are made with Poisson and negative binomial baseline calculations as well as with UrQMD, a transport model (UrQMD) that does not include effects from the QCD critical point. Within current uncertainties, the net-kaon cumulant ratios appear to be monotonic as a function of collision energy.
Comments:
12 pages, 11 figures
Subjects:
Nuclear Experiment (nucl-ex); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1709.00773 [pdf]
PLB(2018)·175 citations
12
[Submitted on 4 Sept 2017] (cross-list from hep-ph)
Hidden-charm and bottom meson-baryon molecules coupled with five-quark states
Yasuhiro Yamaguchi🇯🇵 · Alessandro Giachino🇮🇹 · Atsushi Hosaka🇯🇵 · Elena Santopinto🇮🇹 · Sachiko Takeuchi🇯🇵 · Makoto Takizawa🇯🇵
In this paper, we investigate the hidden-charm pentaquarks as $D ˉ^{(*)} Λ_{c}$ and $D ˉ^{(*)} Σ_{c}^{(*)}$ molecules coupled to the five-quark states. Furthermore, we extend our calculations to the hidden-bottom sector. The coupling to the five-quark states is treated as the short range potential, where the relative strength for the meson-baryon channels is determined by the structure of the five-quark states. We found that resonant and/or bound states appear in both the charm and bottom sectors. The five-quark state potential turned out to be attractive and, for this reason, it plays an important role to produce these states. In the charm sector, we need the five-quark potential in addition to the pion exchange potential in producing bound and resonant states, whereas, in the bottom sector, the pion exchange interaction is strong enough to produce states. Thus, from this investigation, it emerges that the hidden-bottom pentaquarks are more likely to form than their hidden-charm counterparts; for this reason, we suggest that the experimentalists should look for states in the bottom sector.
Comments:
58 pages, 13 figures, and 10 tables, published version
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1709.00819 [pdf]
PRD(2017)·79 citations
13
[Submitted on 4 Sept 2017] (cross-list from hep-ph)
Entropy production and isotropization in Yang-Mills theory with use of quantum distribution function
Hidekazu Tsukiji🇯🇵 · Teiji Kunihiro🇯🇵 · Akira Ohnishi🇯🇵 · Toru T. Takahashi🇯🇵
We investigate thermalization process in relativistic heavy ion collisions in terms of the Husimi-Wehrl (HW) entropy defined with the Husimi function, a quantum distribution function in a phase space. We calculate the semiclassical time evolution of the HW entropy in Yang-Mills field theory with the phenomenological initial field configuration known as the McLerran-Venugopalan model in a non-expanding geometry, which has instabilty triggered by initial field fluctuations. HW-entropy production implies the thermalization of the system and it reflects the underlying dynamics such as chaoticity and instability. By comparing the production rate with the Kolmogorov-Sinaï rate, we find that the HW entropy production rate is significantly larger than that expected from chaoticity. We also show that the HW entropy is finally saturated when the system reaches a quasi-stationary state. The saturation time of the HW entropy is comparable with that of pressure isotropization, which is around $1$ fm/c in the present calculation in the non-expanding geometry.
Comments:
17 pages, 5 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Statistical Mechanics (cond-mat.stat-mech); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th); Quantum Physics (quant-ph)
arXiv:
1709.00979 [pdf]
PTEP(2018)·13 citations

Affiliations

first authorsco-authorsvia INSPIRE