PaperPanorama

Nuclear Theory·nucl-th

Tuesday·September 1, 2020

19 papers9 primary·10 cross-listed

  1. 01

    [Submitted on 31 Aug 2020]

    Robustness of chiral symmetry in atomic nuclei with reflection-asymmetric shapes

    C. M. Petrache🇫🇷

    The present paper is a comment regarding the robustness of the chirality in presence of the space-reflection asymmetry, which leads to pairs of interleaved positive- and negative-parity bands. The recent results reported in Ref. \cite{2006.12062} which introduced the and quantum numbers to describe an ideal nuclear system with simultaneous chiral and reflection symmetry breaking, are commented.

    Subjects:
    Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
    arXiv:
    2008.12781 [pdf]
    Sci.Bull.(2020)·1 citation
  2. 02

    [Submitted on 30 Aug 2020]

    Practical method for decomposing discretized breakup cross sections into components of each channel

    Shin Watanabe · Kazuyuki Ogata · Takuma Matsumoto

    Background: In the continuum-discretized coupled-channel method, a breakup cross section (BUX) is obtained as an admixture of several components of different channels in multi-channel scattering. Purpose: Our goal is to propose an approximate way of decomposing the discretized BUX into components of each channel. This approximation is referred to as the "probability separation (P-separation)". Method: As an example, we consider Be scattering by using the three-body model with core excitation (, where T is a target). The structural part is constructed by the particle-rotor model and the reaction part is described by the distorted wave Born approximation (DWBA). Results: The validity of the P-separation is tested by comparing with the exact calculation. The approximate way reproduces the exact BUXs well regardless of the configurations and/or the resonance positions of Be. Conclusion: The method proposed here can be an alternative approach for decomposing discretized BUXs into components in four- or five-body scattering where the strict decomposition is hard to perform.

    Comments:
    6 pages, 2 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2008.13125 [pdf]
    PRC(2021)·10 citations
  3. 03

    [Submitted on 30 Aug 2020]

    Shell model structure of proxy-SU(3) pairs of orbitals

    Dennis Bonatsos · Hadi Sobhani · Hassan Hassanabadi

    The Nilsson orbitals used in the substitutions occurring in the proxy-SU(3) scheme, which are the orbitals bearing the maximum value of total angular momentum in each shell, have an extremely simple structure in the shell model basis |N l j Omega>, with each Nilsson orbital corresponding to a single shell model eigenvector. This simple structure is valid at all deformations for these orbitals, while in other orbitals it is valid only at small deformations. Nilsson 0[110] pairs are found to correspond to |1 1 1 0> pairs in the spherical shell model basis, paving the way for using the proxy-SU(3) approximation within the shell model.

    Comments:
    10 pages, 5 tables
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2008.13220 [pdf]
    Eur.Phys.J.Plus(2020)·24 citations
  4. 04

    [Submitted on 30 Aug 2020]

    Advances in modeling nuclear matrix elements of neutrinoless double beta decay

    J. M. Yao🇺🇸

    Accurate nuclear matrix elements (NMEs) for neutrinoless double beta decays of candidate nuclei are important for the design and interpretation of future experiments. Significant progress has been made in the modeling of these NMEs from first principles. The NME for 48Ca shows a good agreement among three different ab initio calculations starting from the same nuclear interaction constructed within the chiral EFT and the same decay operator. These studies open the door to ab initio calculations of the matrix elements for the decay of heavier nuclei such as 76Ge, 130Te, and 136Xe. The ultimate goal is the computation of NMEs in many-body calculations with controllable approximations, using nuclear interactions and weak transition operators derived consistently from chiral EFT. We are expecting more progress towards this goal in the near future.

    Comments:
    3 pages, 1 figure. invited contribution to News and Views in Science Bulletin
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
    arXiv:
    2008.13249 [pdf]
    Sci.Bull.(2021)·6 citations
  5. 05

    [Submitted on 30 Aug 2020]

    Breaking SU(3) spectral degeneracies in heavy deformed nuclei

    Dennis Bonatsos · I.E. Assimakis · Andriana Martinou · S. Peroulis · S. Sarantopoulou · N. Minkov

    Symmetries are manifested in nature through degeneracies in the spectra of physical systems. In the case of heavy deformed nuclei, when described in the framework of the Interacting Boson Model, within which correlated proton (neutron) pairs are approximated as bosons, the ground state band has no symmetry partner, while the degeneracy between the first excited beta and gamma bands is broken through the use of three-body and/or four-body terms. In the framework of the proxy-SU(3) model, in which an approximate SU(3) symmetry of fermions is present, the same three-body and/or four-body operators are used for breaking the degeneracy between the ground state band and the first excited gamma band. Experimentally accessible quantities being independent of any free parameters are pointed out in the latter case.

    Comments:
    5 pages, 2 tables, 3 figures. To appear in the electronic proceedings of the the 5th Hellenic Institute of Nuclear Physics Workshop (HINPw5), Thessaloniki, Greece, 12-13 April 2019, edited by Ch. Moustakidis
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2008.13256 [pdf]
    2 citations
  6. 06

    [Submitted on 31 Aug 2020]

    A solvable model for octupole phonons

    P. Van Isacker🇫🇷

    A solvable model is proposed for the description of octupole phonons in closed-shell nuclei, formulated in terms of shell-model par\-ticle--hole excitations. With some simple assumptions concerning single-particle energies and two-body interactions, closed expressions are derived for the energy and wave function of the octupole phonon. In particular, it is shown that the components of the octupole phonon are proportional to Wigner coefficients. This analytic wave function is proven to be exactly valid in light nuclei, which have shell closures that coincide with those of the three-dimensional harmonic oscillator, and to be valid to a good approximation in heavier nuclei, which have shell closures due to the spin--orbit interaction. The properties of the solvable model are compared with the results of a realistic shell-model calculation for Pb.

    Comments:
    16 pages, 4 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2008.13579 [pdf]
    Eur.Phys.J.ST(2020)·5 citations
  7. 07

    [Submitted on 31 Aug 2020]

    Higher-rank discrete symmetries in the IBM. II Octahedral shapes: Dynamical symmetries

    A. Bouldjedri🇩🇿 · S. Zerguine🇩🇿 · P. Van Isacker🇫🇷

    The symmetries of the sdg-IBM, the interacting boson model with s, d and g bosons, are studied as regards the occurrence of shapes with octahedral symmetry. It is shown that no sdg-IBM Hamiltonian with a dynamical symmetry displays in its classical limit an isolated minimum with octahedral shape. However, a degenerate minimum that includes a shape with octahedral symmetry can be obtained from a Hamiltonian that is transitional between two limits, U_g(9) x U_d(5) and SO_sg(10) x U_d(5), and the conditions for its existence are derived. An isolated minimum with octahedral shape, either an octahedron or a cube, may arise through a modification of two-body interactions between the g bosons. Comments on the observational consequences of this construction are made.

    Comments:
    18 pages, 5 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2008.13599 [pdf]
    NPA(2020)·4 citations
  8. 08

    [Submitted on 31 Aug 2020]

    Quantum catastrophes from an algebraic perspective

    A. Leviatan · N. Gavrielov

    We study the properties of quantum cusp and butterfly catastrophes from an algebraic viewpoint. The analysis employs an interacting boson model Hamiltonian describing quantum phase transitions between specific quadrupole shapes by interpolating between two incompatible dynamical symmetry limits. The classical properties are determined by using coherent states to construct the complete phase diagrams associated with Landau potentials exhibiting such catastrophes.The quantum properties are determined by analyzing the spectra, transition rates and symmetry character of the eigenstates of critical Hamiltonians.

    Comments:
    14 pages, 11 figures, talk at Symposium "Symmetries in Science XVIII", August 4-9, 2019, Bregenz, Austria
    Subjects:
    Nuclear Theory (nucl-th); Quantum Physics (quant-ph)
    arXiv:
    2008.13717 [pdf]
    J.Phys.Conf.Ser.(2020)·3 citations
  9. 09

    [Submitted on 31 Aug 2020]

    State densities of heavy nuclei in the static-path plus random-phase approximation

    P. Fanto · Y. Alhassid

    Nuclear state densities are important inputs to statistical models of compound-nucleus reactions. State densities are often calculated with self-consistent mean-field approximations that do not include important correlations and have to be augmented with empirical collective enhancement factors. Here, we benchmark the static-path plus random-phase approximation (SPA+RPA) to the state density in a chain of samarium isotopes Sm against exact results (up to statistical errors) obtained with the shell model Monte Carlo (SMMC) method. The SPA+RPA method incorporates all static fluctuations beyond the mean field together with small-amplitude quantal fluctuations around each static fluctuation. Using a pairing plus quadrupole interaction, we show that the SPA+RPA state densities agree well with the exact SMMC densities for both the even- and odd-mass isotopes. For the even-mass isotopes, we also compare our results with mean-field state densities calculated with the finite-temperature Hartree-Fock-Bogoliubov (HFB) approximation. We find that the SPA+RPA repairs the deficiencies of the mean-field approximation associated with broken rotational symmetry in deformed nuclei and the violation of particle-number conservation in the pairing condensate. In particular, in deformed nuclei the SPA+RPA reproduces the rotational enhancement of the state density relative to the mean-field state density.

    Comments:
    13 pages, 5 figures, 3 tables
    Subjects:
    Nuclear Theory (nucl-th); Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
    arXiv:
    2008.13722 [pdf]
    PRC(2021)·12 citations
  10. 10

    [Submitted on 27 Aug 2020] (cross-list from hep-ph)

    Triple-X and beyond: hadronic systems of three and more X(3872)

    Lorenzo Contessi🇫🇷 · Johannes Kirscher🇬🇧 · Manuel Pavon Valderrama🇨🇳

    The resonance has been conjectured to be a charm meson-antimeson two-body molecule. Meanwhile, there is no experimental evidence for larger, few-body compounds of multiple charm meson-antimeson pairs which would resemble larger molecules or nuclei. Here, we investigate such multi-meson states to the extent of what can be deduced theoretically from essentials of the interaction between uncharged and mesons. From a molecular , we predict a () octamer with a binding energy \mbox{,} assuming a system close to the unitary limit (as suggested by the mass of the ). If we consider heavy-quark spin symmetry explicitly, the () system is close to unitarity, too. In this case, we predict a bound () hexamer with and a more deeply bound octamer with . These results exemplify with hadronic molecules a more general phenomenon of equal-mass two-species Bose systems comprised of equal number of either type: the emergence of unbound four- and six-boson clusters in the limit of a short-range two-body interaction which acts only between bosons of different species. Finally, we also study the conditions under which a () tetramer might form.

    Comments:
    7 pages, 3 figures, corresponds to the published version
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    2008.12268 [pdf]
    PRD(2021)·4 citations
  11. 11

    [Submitted on 28 Aug 2020] (cross-list from astro-ph.HE)

    Combining Electromagnetic and Gravitational-Wave Constraints on Neutron-Star Masses and Radii

    Mohammad Al-Mamun · Andrew W. Steiner · Joonas Nättilä · Jacob Lange · Richard O'Shaughnessy · Ingo Tews · Stefano Gandolfi · Craig Heinke · Sophia Han

    We perform a joint Bayesian inference of neutron-star mass and radius constraints based on GW170817, observations of quiescent low-mass X-ray binaries (QLMXBs), photospheric radius expansion X-ray bursts (PREs), and X-ray timing observations of J0030+0451. With this data set, the form of the prior distribution still has an impact on the posterior mass-radius (MR) curves and equation of state (EOS), but this impact is smaller than recently obtained when considering QLMXBs alone. We analyze the consistency of the electromagnetic data by including an "intrinsic scattering" contribution to the uncertainties, and find only a slight broadening of the posteriors. This suggests that the gravitational-wave and electromagnetic observations of neutron-star structure are providing a consistent picture of the neutron-star mass-radius curve and the EOS.

    Comments:
    6 pages, 4 figures and supplemental material
    Subjects:
    High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Theory (nucl-th)
    arXiv:
    2008.12817 [pdf]
    PRL(2021)·111 citations
  12. 12

    [Submitted on 29 Aug 2020] (cross-list from physics.atom-ph)

    Nonlinear optical effects in a nucleus

    Tao Li🇨🇳 · Xu Wang🇨🇳

    Intense laser technologies generate light with unprecedented and growing intensities. The possibility emerges that a nucleus responds nonlinearly to an intense light field, pointing to a yet little explored research area of nuclear nonlinear optics. We consider two-photon and three-photon absorption (with subsequent disintegration) processes of the deuteron, the simplest and the most fundamental nontrivial nucleus, as prototypes of nuclear nonlinear optical effects. Quantitative calculations are performed on these processes and novel observable effects are predicted.

    Subjects:
    Atomic Physics (physics.atom-ph); Nuclear Theory (nucl-th)
    arXiv:
    2008.12956 [pdf]
    J.Phys.G(2021)·6 citations
  13. 13

    [Submitted on 31 Aug 2020] (cross-list from hep-ph)

    Gradient tomography of jet quenching in high-energy heavy-ion collisions

    Yayun He🇨🇳 · Longgang Pang🇨🇳 · Xin-Nian Wang🇨🇳

    We illustrate with both a Boltzmann diffusion equation and full simulations of jet propagation in heavy-ion collisions within the Linear Boltzmann Transport (LBT) model that the spatial gradient of the jet transport coefficient perpendicular to the propagation direction can lead to a drift and asymmetry in the transverse momentum distribution. Such an asymmetry depends on both the spatial position along the transverse gradience and the propagating length. It can be used to localize the initial jet production positions for more detailed studies of jet quenching and properties of the quark-gluon plasma in heavy-ion collisions.

    Comments:
    4 pages in Latex format for POS with 4 PDF figures, prepared for publication in the proceedings of Hard Probes 2020 conference, 1-6 June 2020, Austin, Texas
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    2008.13304 [pdf]
    PoS(2021)·1 citation
  14. 14

    [Submitted on 31 Aug 2020] (cross-list from hep-ph)

    Near-threshold photoproduction of in two-gluon exchange model

    Fancong Zeng🇨🇳 · Xiao-Yun Wang🇨🇳 · Li Zhang🇨🇳 · Ya-Ping Xie🇨🇳 · Rong Wang🇨🇳 · Xurong Chen🇨🇳

    The near-threshold photoproduction of is regarded as one golden process to unveil the nucleon mass structure, pentaquark state involving the charm quarks, and the poorly constrained gluon distribution of the nucleon at large (). In this paper, we present an analysis of the current experimental data under a two-gluon exchange model, which shows a good consistency. Using a parameterized function form with three free parameters, we have determined the nucleonic gluon distribution at the mass scale. Moreover, we predict the differential cross section of the electroproduction of as a function of the invariant mass of the final hadrons , at EicC, as a practical application of the model and the obtained gluon distribution. According to our estimation, thousands of events can be detected per year on EicC near the threshold. Therefore, the relevant experimental measurements are suggested to be carried out on EicC.

    Comments:
    6 pages, 7 figures
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    2008.13439 [pdf]
    EPJC(2020)·21 citations
  15. 15

    [Submitted on 31 Aug 2020] (cross-list from hep-ph)

    Evidence of shadowing in inelastic nucleon-nucleon cross section

    Kari J. Eskola🇫🇮 · Ilkka Helenius🇫🇮 · Mikko Kuha🇫🇮 · Hannu Paukkunen

    The Glauber modeling plays a key role in centrality-dependent measurements of heavy-ion collisions. A central input parameter in Glauber models is the inelastic nucleon-nucleon cross section which is nearly always taken from proton-proton measurements. At the LHC energies depends on the QCD dynamics at small and low interaction scales where the shadowing/saturation phenomena are expected to become relatively more important for larger nuclei than for the proton. Thus, e.g. in Pb+Pb collisions may well be lower than what is seen in proton-proton collisions. In this talk, we demonstrate how to use the recent and measurements as a "standard candle" to extract in Pb+Pb collisions. Our analysis -- built on the ATLAS data, state-of-the-art NNLO QCD calculations and nuclear PDFs -- indicate that at the LHC energies in Pb+Pb collisions is suppressed relative to the proton-proton measurements by tens of percents. We demonstrate that this is in line with expectations from nuclear PDFs.

    Comments:
    5 pages, 4 figures, to appear in the proceedings of the 10th International Conference on Hard and Electromagnetic Probes of High-Energy Nuclear Collisions, 1 - 5 June 2020, Austin, Texas, USA
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    2008.13448 [pdf]
    PoS(2021)·2 citations
  16. 16

    [Submitted on 31 Aug 2020] (cross-list from hep-ph)

    (2900) and invariant mass from QCD Laplace sum rules at NLO

    R.M. Albuquerque🇧🇷 · S. Narison🇫🇷 · D. Rabetiarivony🇲🇬 · G. Randriamanatrika🇲🇬

    We revisit, improve and complete some recent estimates of the and open charm tetraquarks and the corresponding molecules masses and decay constants from QCD spectral sum rules (QSSR) by using QCD Laplace sum rule (LSR) within stability criteria where the factorised perturbative NLO corrections and the contributions of quark and gluon condensates up to dimension-6 in the OPE are included. We confront our results with the invariant mass recently reported by LHCb from decays. We expect that the bump near the threshold can be originated from the molecule and/or scattering. The prominent (2900) scalar peak and the bump (if ) can emerge from a {\it minimal mixing model}, with a tiny mixing angle , between a scalar {\it Tetramole} () (superposition of nearly degenerated hypothetical molecules and compact tetraquarks states with the same quantum numbers) having a mass =2743(18) MeV and the first radial excitation of the molecule with mass MeV. In an analogous way, the (2900) and the (if ) could be a mixture between the vector {\it Tetramole} with a mass MeV and its first radial excitation having a mass MeV with an angle . A (non)-confirmation of the previous {\it minimal mixing models} requires an experimental identification of the quantum numbers of the bumps at 3150 and 3350 MeV.

    Comments:
    28 pages, 15 Figures, 5 Tables - Version to appear in Nuclear Physics A after some minor corrections on proofs
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
    arXiv:
    2008.13463 [pdf]
    NPA(2021)·58 citations
  17. 17

    [Submitted on 31 Aug 2020] (cross-list from hep-ph)

    Cosmological particle creation in the little bang

    S.V. Akkelin🇺🇦

    Particle production by expanding in the future light cone scalar quantum field is studied by assuming that the initial state is associated with the quasiequilibrium statistical operator corresponding to fluid dynamics. We calculate particle production from a longitudinally boost-invariant expanding quantum field designed as a simple but reliable model for the central rapidity region of a relativistic collision. Exact diagonalization of the model is performed by introducing a notion of quasiparticles.

    Comments:
    17 pages
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
    arXiv:
    2008.13606 [pdf]
    PRD(2021)·6 citations
  18. 18

    [Submitted on 31 Aug 2020] (cross-list from astro-ph.HE)

    Medium modifications for light and heavy nuclear clusters in simulations of core collapse supernovae -- Impact on equation of state and weak interactions

    Tobias Fischer · Stefan Typel · Gerd Röpke · Niels-Uwe F. Bastian · Gabriel Martínez-Pinedo

    The present article investigates the role of heavy nuclear clusters and weakly bound light nuclear clusters based on a newly developed equation of state for core collapse supernova studies. A novel approach is brought forward for the description of nuclear clusters, taking into account the quasiparticle approach and continuum correlations. It demonstrates that the commonly employed nuclear statistical equilibrium approach, based on non-interacting particles, for the description of light and heavy clusters becomes invalid for warm nuclear matter near the saturation density. This has important consequences for studies of core collapse supernovae. To this end, we implement this nuclear equation of state provided for arbitrary temperature, baryon density and isospin asymmetry, to spherically symmetric core collapse supernova simulations in order to study the impact on the dynamics as well as on the neutrino emission. For the inclusion of a set of weak processes involving light clusters the rate expressions are derived, including medium modifications at the mean field level. A substantial impact from the inclusion of a variety of weak reactions involving light clusters on the post bounce dynamics nor on the neutrino emission could not be found.

    Comments:
    24 pages, 9 figures
    Subjects:
    High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
    arXiv:
    2008.13608 [pdf]
    PRC(2020)·34 citations
  19. 19

    [Submitted on 27 Aug 2020] (cross-list from hep-ph)

    Study of Transverse Spherocity and Azimuthal Anisotropy in Pb-Pb collisions at = 5.02 TeV using A Multi-Phase Transport Model

    Neelkamal Mallick🇮🇳 · Raghunath Sahoo🇮🇳 · Sushanta Tripathy🇲🇽 · Antonio Ortiz🇲🇽

    Transverse spherocity is an event shape observable having a very unique capability to separate the events based on their geometrical shapes. Recent results from experiments at the LHC suggest that transverse spherocity is an important event classifier in small collision systems. In this work, we use transverse spherocity for the first time in heavy-ion collisions and perform an extensive study on azimuthal anisotropy of charged particles produced in Pb-Pb collisions at TeV using A Multi-Phase Transport Model (AMPT). The azimuthal anisotropy is estimated using the 2-particle correlation method, which suppresses the non-flow effects significantly with an appropriate pseudorapidity gap of particle pairs. The results from AMPT are compared with estimations from PYTHIA8 (Angantyr) model and it is found that with the chosen pseudorapidity gap the residual non-flow effects become negligible. We found that the high spherocity events have nearly zero elliptic flow while low spherocity events contribute significantly to elliptic flow of spherocity-integrated events. Our studies indicate that using transverse spherocity in heavy-ion collisions, one can enhance and/or suppress the collective effects.

    Comments:
    Same as the published version. arXiv admin note: text overlap with arXiv:2001.06849
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    2008.13616 [pdf]
    J.Phys.G(2021)·35 citations

Affiliations

first authorsco-authorsvia INSPIRE