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Nuclear Theory·nucl-th

Tuesday·October 10, 2017

20 papers—11 primary·9 cross-listed

All20Primary11Cross-lists9
  1. 01

    [Submitted on 6 Oct 2017]

    Li in a Three-Body Model with Realistic Forces: Separable vs. Non-separable Approach

    L. Hlophe🇺🇸 · Jin Lei🇺🇸 · Ch. Elster🇺🇸 · A. Nogga🇩🇪 · F.M. Nunes🇺🇸

    {\bf Background:} Deuteron induced reactions are widely used to probe nuclear structure and astrophysical information. Those (d,p) reactions may be viewed as three-body reactions and described with Faddeev techniques. {\bf Purpose:} Faddeev equations in momentum space have a long tradition of utilizing separable interactions in order to arrive at sets of coupled integral equations in one variable. However, it needs to be demonstrated that their solution based on separable interactions agrees exactly with solutions based on non-separable forces. {\bf Results:} The ground state of Li is calculated via momentum space Faddeev equations using the CD-Bonn neutron-proton force and a Woods-Saxon type neutron(proton)-He force. For the latter the Pauli-forbidden -wave bound state is projected out. This result is compared to a calculation in which the interactions in the two-body subsystems are represented by separable interactions derived in the Ernst-Shakin-Thaler framework. {\bf Conclusions:} We find that calculations based on the separable representation of the interactions and the original interactions give results that agree to four significant figures for the binding energy, provided an off-shell extension of the EST representation is employed in both subsystems. The momentum distributions computed in both approaches also fully agree with each other.

    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1710.02602 [pdf]
    PRC(2017)·14 citations
  2. 02

    [Submitted on 8 Oct 2017]

    -cluster states in Cr from double-folding potentials

    Peter Mohr

    --cluster states in Cr and Cr are investigated in the double-folding model. This study complements a recent similar work of Souza and Miyake \cite{Sou17} which was based on a specially shaped potential. Excitation energies, reduced widths, intercluster separations, and intra-band transition strengths are calculated and compared to experimental values for the ground state bands in Cr and Cr. The -cluster potential is also applied to elastic scattering at low and intermediate energies. Here, as a byproduct, a larger radial extent of the neutron density in Ti is found.

    Comments:
    9 pages, 7 figures, Europ. Phys. J. A, accepted for publication
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1710.02790 [pdf]
    EPJA(2017)·14 citations
  4. 04

    [Submitted on 8 Oct 2017]

    Nuclear Axial Currents from Scale-Chiral Effective Field Theory

    Yan-Ling Li🇨🇳 · Yong-Liang Ma🇨🇳 · Mannque Rho🇫🇷

    By incorporating hidden scale symmetry and hidden local symmetry in nuclear effective field theory, combined with double soft-pion theorem, we predict that the Gamow-Teller operator coming from the space component of the axial current should remain unaffected by the QCD vacuum change caused by baryonic density whereas the first forbidden beta transition operator coming from the time component should be strongly enhanced. While the latter has been confirmed since some time, the former is given a support by a powerful recent {\it ab initio} quantum Monte Carlo calculation in light nuclei, also confirming the old "chiral filter hypothesis." Formulated in terms of Fermi-liquid fixed point structure of strong-coupled nuclear interactions, we offer an extremely simple resolution to the long-standing puzzle of "quenched ", ~\cite{quenched}, in nuclear Gamow-Teller beta transitions, giant Gamow-Teller resonances and double beta decays.

    Comments:
    More discussions are added. Several typos are corrected
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    1710.02840 [pdf]
    CPC(2018)·13 citations
  5. 05

    [Submitted on 8 Oct 2017]

    Level density of the -nuclei statistical shell-model predictions

    S. Karampagia · R. A. Senkov · V. Zelevinsky

    Accurate knowledge of the nuclear level density is important both from a theoretical viewpoint as a powerful instrument for studying nuclear structure and for numerous applications. For example, astrophysical reactions responsible for the nucleosynthesis in the universe can be understood only if we know the nuclear level density. We use the configuration-interaction nuclear shell model to predict nuclear level density for all nuclei in the -shell, both total and for individual spins (only with positive parity). To avoid the diagonalization in large model spaces we use the moments method based on statistical properties of nuclear many-body systems. In the cases where the diagonalization is possible, the results of the moments method practically coincide with those from the shell-model calculations. Using the computed level densities, we fit the parameters of the Constant Temperature phenomenological model, which can be used by practitioners in their studies of nuclear reactions at excitation energies appropriate for the -shell nuclei.

    Comments:
    106 pages, 7 figures, 109 tables
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1710.02885 [pdf]
    Atom.Data Nucl.Data Tabl.(2018)·13 citations
  6. 06

    [Submitted on 9 Oct 2017]

    Green's function method for the single-particle resonances in a deformed Dirac equation

    T.-T. Sun · L. Qian · C. Chen · P. Ring · Z. P. Li

    Single-particle resonances are crucial for exotic nuclei near and beyond the drip lines. Since the majority of nuclei are deformed, the interplay between deformation and orbital structure near threshold becomes very important and can lead to an improved description of exotic nuclei. In this work, the Green's function (GF) method is applied to solve the coupled-channel Dirac equation with quadrupole-deformed Woods-Saxon potentials for the first time. The detailed formalism for the partial-wave expansion of the Green's function is presented. A new approach getting exact values for energies and widths of resonant states by the GF method is proposed. Numerical checks are carried out by comparing with our previous implementation of the spherical GF method and the results from the deformed complex momentum representation~(CMR), the analytical continuation of the coupling constant (ACCC), and the scattering phase shift (SPS) methods, and it is proved that the GF method is very effective and reliably for describing resonance states, no matter they are narrow or broad, spherical or deformed. Finally, Nilsson levels for bound and resonant orbitals in the halo candidate nucleus Mg are calculated from the deformed GF method over a wide range of deformations and some decisive hints of -wave halo formation are shown in this nucleus, namely, the crossing between the configurations and at deformation parameter may enhance the probability to occupy the orbital that is originated from the shell.

    Comments:
    11pages, 5 figures, 2 tables
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1710.02923 [pdf]
    PRC(2020)·32 citations
  7. 07

    [Submitted on 9 Oct 2017]

    decay properties of nucleus Og within two-potential approach

    Jun-Gang Deng · Jun-Hao Cheng · Bo Zheng · Xiao-Hua Li

    The decay half-life of unknown nucleus Og is predicted within two-potential approach, and preformation probabilities of 64 odd- nuclei in the region of proton numbers and neutron numbers from Cf to Og are extracted. In addition, based on the latest experimental data, a new set of parameters for preformation probabilities considering the shell effect and proton-neutron interaction are obtained. The predicted decay half-life of Og is 0.16 ms within a factor of 4.97 as well as the spin and parity of ground states for nuclei Sg, Fl and Lv are , and , respectively.

    Comments:
    Chinese Physics C (2017) in press
    Subjects:
    Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
    arXiv:
    1710.03008 [pdf]
    CPC(2017)·26 citations
  8. 08

    [Submitted on 9 Oct 2017]

    Effects of initial-state dynamics on collective flow within a coupled transport and viscous hydrodynamic approach

    Chandrodoy Chattopadhyay🇮🇳 · Rajeev S. Bhalerao🇮🇳 · Jean-Yves Ollitrault🇫🇷 · Subrata Pal🇮🇳

    We evaluate the effects of preequilibrium dynamics on observables in ultrarelativistic heavy-ion collisions. We simulate the initial nonequilibrium phase within A MultiPhase Transport (AMPT) model, while the subsequent near-equilibrium evolution is modeled using (2+1)-dimensional relativistic viscous hydrodynamics. We match the two stages of evolution carefully by calculating the full energy-momentum tensor from AMPT and using it as input for the hydrodynamic evolution. We find that when the preequilibrium evolution is taken into account, final-state observables are insensitive to the switching time from AMPT to hydrodynamics. Unlike some earlier treatments of preequilibrium dynamics, we do not find the initial shear viscous tensor to be large. With a shear viscosity to entropy density ratio of , our model describes quantitatively a large set of experimental data on Pb+Pb collisions at the Large Hadron Collider(LHC) over a wide range of centrality: differential anisotropic flow , event-plane correlations, correlation between and , and cumulant ratio .

    Comments:
    10 pages, v2: minor revision
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
    arXiv:
    1710.03050 [pdf]
    PRC(2018)·21 citations
  9. 09

    [Submitted on 9 Oct 2017]

    Importance of isobar density distributions on the chiral magnetic effect search

    Hao-jie Xu🇨🇳 · Xiaobao Wang🇨🇳 · Hanlin Li🇨🇳 · Jie Zhao🇺🇸 · Zi-Wei Lin🇺🇸 · Caiwan Shen🇨🇳 · Fuqiang Wang🇨🇳

    Under the approximate chiral symmetry restoration, quark interactions with topological gluon fields in quantum chromodynamics can induce chirality imbalance and parity violation in local domains. An electric charge separation ({\sc cs}) could be generated along the direction of a strong magnetic field ({\bf B}), a phenomenon called the chiral magnetic effect ({\sc cme}). {\sc cs} measurements by azimuthal correlators are contaminated by a major background from elliptic flow anisotropy (). Isobaric Ru+Ru and Zr+Zr collisions have been proposed to identify the {\sc cme} (expected to differ between the two systems) out of the background (expected to be almost the same). We show, by using the density-functional calculated proton and neutron distributions, that these expectations may not hold as originally anticipated, because the two systems may have sizable differences in eccentricity and and because their difference in {\bf B} may suffer from large uncertainties.

    Comments:
    6 pages, 4 figures. v2: Now the magnetic field averaged over the overlap area is presented, instead of that at the single point at the overlap center in the previous version. v3: published version
    Subjects:
    Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
    arXiv:
    1710.03086 [pdf]
    PRL(2018)·110 citations
  10. 10

    [Submitted on 9 Oct 2017]

    Hubbard-Stratonovich-like Transformations for Few-Body Interactions

    Christopher Körber · Evan Berkowitz · Thomas Luu

    Through the development of many-body methodology and algorithms, it has become possible to describe quantum systems composed of a large number of particles with great accuracy. Essential to all these methods is the application of auxiliary fields via the Hubbard-Stratonovich transformation. This transformation effectively reduces two-body interactions to interactions of one particle with the auxiliary field, thereby improving the computational scaling of the respective algorithms. The relevance of collective phenomena and interactions grows with the number of particles. For many theories, e.g. Chiral Perturbation Theory, the inclusion of three-body forces has become essential in order to further increase the accuracy on the many-body level. In this proceeding, the analytical framework for establishing a Hubbard-Stratonovich-like transformation, which allows for the systematic and controlled inclusion of contact three- and more-body interactions, is presented.

    Comments:
    Conference proceeding, 8 pages, 4 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1710.03126 [pdf]
    EPJ Web Conf.(2018)·2 citations
  11. 11

    [Submitted on 9 Oct 2017]

    Transition sum rules in the shell model

    Yi Lu · Calvin W. Johnson

    An important characterization of electromagnetic and weak transitions in atomic nuclei are sum rules. We focus on the non-energy-weighted sum rule (NEWSR), or total strength, and the energy-weighted sum rule (EWSR); the ratio of the EWSR to the NEWSR is the centroid or average energy of transition strengths from an nuclear initial state to all allowed final states. These sum rules can be expressed as expectation values of operators, in the case of the EWSR a double commutator. While most prior applications of the double-commutator have been to special cases, we derive general formulas for matrix elements of both operators in a shell model framework (occupation space), given the input matrix elements for the nuclear Hamiltonian and for the transition operator. With these new formulas, we easily evaluate centroids of transition strength functions, with no need to calculate daughter states. We apply this simple tool to a number of nuclides, and demonstrate the sum rules follow smooth secular behavior as a function of initial energy, as well as compare the electric dipole (E1) sum rule against the famous Thomas-Reiche-Kuhn version. We also find surprising systematic behaviors for ground state electric quadrupole (E2) centroids in the -shell.

    Comments:
    3 figures (updated); paper updated to reflect accepted version
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1710.03187 [pdf]
    PRC(2018)·16 citations
  12. 12

    [Submitted on 6 Oct 2017] (cross-list from hep-ph)

    Spectroscopy and decays of the fully-heavy tetraquarks

    Muhammad Naeem Anwar🇩🇪 · Jacopo Ferretti🇨🇳 · Feng-Kun Guo🇨🇳 · Elena Santopinto🇮🇹 · Bing-Song Zou🇨🇳

    We discuss the possible existence of the fully-heavy tetraquarks. We calculate the ground-state energy of the bound state, where stands for the bottom quark, in a nonrelativistic effective field theory framework with one-gluon-exchange (OGE) color Coulomb interaction, and in a relativized diquark model characterized by OGE plus a confining potential. Our analysis advocates the existence of uni-flavor heavy four-quark bound states. The ground state tetraquark mass is predicted to be ~GeV. Mass inequality relations among the lowest state, where , and the corresponding heavy quarkonia are presented, which give the upper limit on the mass of ground state . The possible decays of the lowest are highlighted, which might provide useful references in the search for them in ongoing LHC experiments, and its width is estimated to be a few tens of MeV.

    Comments:
    Version accepted for publication in Eur. Phys. J. C
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
    arXiv:
    1710.02540 [pdf]
    EPJC(2018)·172 citations
  13. 13

    [Submitted on 6 Oct 2017] (cross-list from nucl-ex)

    Roper resonance -- solution to the fifty year puzzle

    Volker D. Burkert🇺🇸 · Craig D. Roberts🇺🇸

    For half a century, the Roper resonance has defied understanding. Discovered in 1963, it appears to be an exact copy of the proton except that its mass is 50% greater. The mass is the first problem: it is difficult to explain with any theoretical tool that can validly be used to study quantum chromodynamics [QCD]. In the last decade, a new challenge has appeared, viz. precise information on the proton-to-Roper electroproduction transition form factors, reaching GeV. This scale probes the domain within which hard valence-quark degrees-of-freedom could be expected to determine form factor behavior. Hence, with this new data the Roper resonance becomes a problem for strong-QCD [sQCD]. An explanation of how and where the Roper resonance fits into the emerging spectrum of hadrons cannot rest on a description of its mass alone. Instead, it must combine this with a detailed understanding of the Roper's structure and how that is revealed in the transition form factors. Furthermore, it must unify all this with a similarly complete picture of the proton. This is a prodigious task, but a ten-year international effort, drawing together experimentalists and theorists, has presented a solution to the puzzle. Namely, the Roper is at heart the proton's first radial excitation, consisting of a dressed-quark core augmented by a meson cloud that reduces the core mass by approximately 20% and materially alters its electroproduction form factors on , where is the proton's mass. We describe the experimental motivations and developments which enabled electroproduction data to be procured within a domain that is unambiguously the purview of sQCD, thereby providing a real challenge and opportunity for modern theory; and survey the developments in reaction models and QCD theory that have enabled this conclusion to be drawn about the nature of the Roper resonance.

    Comments:
    23 pages, 19 figures
    Subjects:
    Nuclear Experiment (nucl-ex); High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1710.02549 [pdf]
    RMP(2019)·161 citations
  14. 14

    [Submitted on 7 Oct 2017] (cross-list from hep-lat)

    Improved real-time dynamics from imaginary frequency lattice simulations

    Jan M. Pawlowski🇩🇪 · Alexander Rothkopf🇩🇪

    The computation of real-time properties, such as transport coefficients or bound state spectra of strongly interacting quantum fields in thermal equilibrium is a pressing matter. Since the sign problem prevents a direct evaluation of these quantities, lattice data needs to be analytically continued from the Euclidean domain of the simulation to Minkowski time, in general an ill-posed inverse problem. Here we report on a novel approach to improve the determination of real-time information in the form of spectral functions by setting up a simulation prescription in imaginary frequencies. By carefully distinguishing between initial conditions and quantum dynamics one obtains access to correlation functions also outside the conventional Matsubara frequencies. In particular the range between and , which is most relevant for the inverse problem may be more highly resolved. In combination with the fact that in imaginary frequencies the kernel of the inverse problem is not an exponential but only a rational function we observe significant improvements in the reconstruction of spectral functions, demonstrated in a simple 0+1 dimensional scalar field theory toy model.

    Comments:
    8 pages, 5 figures, Talk given at the XXXVth International Symposium on Lattice Field Theory, June 18-24, 2017, Granada, Spain
    Subjects:
    High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
    arXiv:
    1710.02672 [pdf]
    EPJ Web Conf.(2018)·2 citations
  15. 15

    [Submitted on 7 Oct 2017] (cross-list from hep-ph)

    S-matrix analysis of the baryon electric charge correlation

    Pok Man Lo🇩🇪 · Bengt Friman🇩🇪 · Krzysztof Redlich🇩🇪 · Chihiro Sasaki🇵🇱

    We compute the correlation of the net baryon number with the electric charge () for an interacting hadron gas using the S-matrix formulation of statistical mechanics. The observable is particularly sensitive to the details of the pion-nucleon interaction, which are consistently incorporated in the current scheme via the empirical scattering phase shifts. Comparing to the recent lattice QCD studies in the -flavor system, we find that the natural implementation of interactions and the proper treatment of resonances in the S-matrix approach lead to an improved description of the lattice data over that obtained in the hadron resonance gas model.

    Comments:
    6 pages, 2 figures, submitted to phys. lett. b
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1710.02711 [pdf]
    PLB(2018)·59 citations
  16. 16

    [Submitted on 7 Oct 2017] (cross-list from hep-ph)

    Average CsI neutron density distribution from COHERENT data

    M. Cadeddu🇮🇹 · C. Giunti🇮🇹 · Y.F. Li🇨🇳 · Y.Y. Zhang🇨🇳

    Using the coherent elastic neutrino-nucleus scattering data of the COHERENT experiment, we determine for the first time the average neutron rms radius of and . We obtain the practically model-independent value using the symmetrized Fermi and Helm form factors. We also point out that the COHERENT data show a evidence of the nuclear structure suppression of the full coherence.

    Comments:
    6 pages. To be published in Physical Review Letters
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    1710.02730 [pdf]
    PRL(2018)·158 citations
  17. 17

    [Submitted on 8 Oct 2017] (cross-list from hep-ph)

    X(3872): propagating in a dense medium

    K. Azizi🇹🇷 · N. Er🇹🇷

    In cold nuclear matter, the shifts in the mass and current-meson coupling as well the vector self energy of the exotic are calculated using the diquark-antidiquark current within the framework of the in-medium two-point QCD sum rule. At the rest frame of the medium, the three momentum of the considered particle is fixed to remove the contributions of the particles with negative energy. In the calculations, we include the in-medium condensates of quark-quark, gluon-gluon and quark-gluon. It is observed that, the shift due to the nuclear matter is negative and is about when the saturation density is used. Such shift is considerably large and comparable with the nucleon' mass shift due to the nuclear medium. The negative shift in the current-meson coupling due to nuclear matter is approximately . At the saturation density, the vector self energy of the exotic state is found to be GeV. It is shown that the mass, current-meson coupling and vector self energy of strongly depend on the density of cold nuclear matter.

    Comments:
    11 Pages, 3 Figures and 1 Table. A typo was corrected
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
    arXiv:
    1710.02806 [pdf]
    NPB(2018)·29 citations
  18. 18

    [Submitted on 8 Oct 2017] (cross-list from hep-ph)

    Derivation of Brown-Rho scaling from scale-chiral perturbation theory

    Yan-Ling Li🇨🇳 · Yong-Liang Ma🇨🇳

    The medium modified hadron properties are studied by using the scale-chiral perturbation theory PT in which the lightest scalar meson is included as an explicit degree of freedom by regarding it as the Nambu-Goldstone boson of scale symmetry both spontaneously broken and explicitly broken by the QCD trace anomaly. We derive Brown-Rho scaling at the leading order of scale symmetry from PT and formulate how to make higher-order scale-chiral corrections going beyond the leading order of scale symmetry. By taking into account the intrinsic density dependence given by the dilaton condensate in the "bare" parameters of the Lagrangian, the medium modified hadron properties are investigated. Relying on available experimental information and certain reasonable assumptions, we arrive at the leading order scale symmetric effective theory that can be confronted with nature .

    Comments:
    10 pages
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1710.02839 [pdf]
    8 citations
  19. 19

    [Submitted on 8 Oct 2017] (cross-list from hep-ph)

    Rotating Dirac fermions in a magnetic field in 1+2,3 dimensions

    Yizhuang Liu🇺🇸 · Ismail Zahed🇺🇸

    We consider the effects of an external magnetic field on rotating fermions in 1+2,3 dimensions. The dual effect of a rotation parallel to the magnetic field causes a net increase in the fermionic density by centrifugation, which follows from the sinking of the particle lowest Landau level in the Dirac sea for free Dirac fermions. In 1+d = 2n dimensions, this effect is related to the chiral magnetic effect in 2n-2 dimensions. This phenomenon is discussed specifically for both weak and strong inter-fermion interactions in 1+2 dimensions. For QCD in 1+3 dimensions with Dirac quarks, we show that in the strongly coupled phase with spontaneously broken chiral symmetry, this mechanism reveals itself in the form of an induced pion condensation by centrifugation. We use this observation to show that this effect causes a shift in the chiral condensate in leading order, and to discuss the possibility for the formation of a novel pion super-fluid phase in present heavy ion collisions at collider energies.

    Comments:
    20 pages, 14 figures
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
    arXiv:
    1710.02895 [pdf]
    PRD(2018)·25 citations
  20. 20

    [Submitted on 9 Oct 2017] (cross-list from hep-ph)

    Re-examining the resonance in the reaction

    Ling-Yun Dai🇩🇪 · Johann Haidenbauer🇩🇪 · Ulf-G. Meißner🇩🇪

    The reaction is investigated at energies close to the threshold with emphasis on the role played by the resonance. The interaction in the final system, constructed within chiral effective field theory and supplemented by a pole diagram that represents a bare resonance, is taken into account rigorously. The pole parameters of the are extracted and found to be compatible with the ones of the resonance that have been established in the reaction . The actual result for the is MeV and MeV. Predictions for the electromagnetic form factors in the timelike region are presented.

    Comments:
    11 pages, 3 figures
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1710.03142 [pdf]
    PRD(2017)·48 citations

Affiliations

first authorsco-authorsvia INSPIRE