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Nuclear Theory·nucl-th

Monday·March 19, 2018

7 papers—5 primary·2 cross-listed

All7Primary5Cross-lists2
  1. 01

    [Submitted on 15 Mar 2018]

    Asymmetric regularization of the ground and excited state of the helium-4 nucleus

    Johannes Kirscher · Harald W. Grießhammer

    We find the threshold structure of the two- and three-nucleon systems, with the deuteron and 3H/3He as the only bound nuclei, sufficient to predict a pair of four-nucleon states: a deeply bound state which is identified with the helium-4 ground state, and a shallow, unstable state at an energy 0.38(25) MeV above the triton-proton threshold which is consistent with data on the first excited state of helium-4. The analysis employs the framework of Pionless EFT at leading order with a generalized regulator prescription which probes renormalization-group invariance of the two states with respect to higher-order perturbations including asymmetrical disturbances of the short-distance structure of the interaction. In addition to this invariance of the bound-state spectrum and the diagonal triton-proton 1S0 phase shifts in the helium-4 channel with respect to the short-distance structure of the nuclear interaction, our multi-channel calculations with a resonating-group method demonstrate the increasing sensitivity of nuclei to the neutron-proton P-wave interaction. We show that two-nucleon phase shifts, the triton channel, and three-nucleon negative-parity channels are less sensitive with respect to enhanced two-nucleon P-wave attraction than the four-nucleon triton-proton 1S0 phase shifts.

    Comments:
    13 pages, 7 figures, 1 table
    Subjects:
    Nuclear Theory (nucl-th); Atomic Physics (physics.atom-ph)
    arXiv:
    1803.05949 [pdf]
    EPJA(2018)·5 citations
  2. 02

    [Submitted on 16 Mar 2018]

    Chiral kinetic approach to the chiral magnetic effect in isobaric collisions

    Yifeng Sun🇺🇸 · Che Ming Ko🇺🇸

    Based on the chiral kinetic approach using quarks and antiquarks from a multiphase transport model as initial conditions, we study the chiral magnetic effect, i.e., the magnetic field induced separation of charged particles in the transverse plane, in non-central isobaric collisions of ZrZr and RuRu, which have the same atomic number but different proton numbers. For the observable related to the difference between the correlations of particles of opposite charges and of same charges, we find a difference between the two collision systems if the magnetic field has a long lifetime of 0.6 fm and the observable is evaluated using the initial reaction plane. This signal of the chiral magnetic effect becomes smaller and comparable to the background contributions from elliptic flow if the event plane determined from particle emission angles is used. For the other observable given by the correlator related to the distribution of average charge separation in a collision, the signal due to the chiral magnetic effect is found to depend less on whether the reaction or event plane is used in the analysis, and their difference between the two isobaric collision systems is thus a more robust observable.

    Comments:
    9 pages and 8 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1803.06043 [pdf]
    PRC(2018)·46 citations
  3. 03

    [Submitted on 16 Mar 2018]

    Collective motion in prolate {\gamma}-rigid nuclei within minimal length concept via a quantum perturbation method

    M. Chabab · A. El Batoul · A. Lahbas · M. Oulne

    Based on the minimal length concept, inspired by Heisenberg algebra, a closed analytical formula is derived for the energy spectrum of the prolate {\gamma}-rigid Bohr-Mottelson Hamiltonian of nuclei, within a quantum perturbation method (QPM), by considering a scaled Davidson potential in \b{eta} shape variable. In the resulting solution, called X(3)-D-ML, the ground state and the first \b{eta}-band are all studied as a function of the free parameters. The fact of introducing the minimal length concept with a QPM makes the model very flexible and a powerful approach to describe nuclear collective excitations of a variety of vibrational-like nuclei. The introduction of scaling parameters in the Davidson potential enables us to get a physical minimum of this latter in comparison with previous works. The analysis of the corrected wave function, as well as the probability density distribution, shows that the minimal length parameter has a physical upper bound limit.

    Comments:
    17p, 9 figs, 2 tables (accepted for publication in Annals of Physics)
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1803.06220 [pdf]
    Annals Phys.(2018)·13 citations
  4. 04

    [Submitted on 16 Mar 2018]

    Superfluid liquid crystals: pasta phases in neutron star crusts

    D. N. Kobyakov · C. J. Pethick

    The pasta phases predicted to occur near the inner boundary of the crust of a neutron star resemble liquid crystals, a smectic A in the case of sheet-like nuclei (lasagna) and the columnar phase in the case of rod-like nuclei (spaghetti). An important difference compared with usual liquid crystals is that the nucleons are superfluid. We develop the hydrodynamic equations for this system and use them to study collective oscillations. Nucleon superfluidity leads to important qualitative differences in the spectra of these oscillations and also increases their frequencies compared with ordinary liquid crystals. We discuss a number of directions for future work.

    Comments:
    7 pages
    Subjects:
    Nuclear Theory (nucl-th); Fluid Dynamics (physics.flu-dyn)
    arXiv:
    1803.06254 [pdf]
    Zh.Eksp.Teor.Fiz.(2018)·14 citations
  5. 05

    [Submitted on 14 Mar 2018]

    Theory of Single Charge Exchange Heavy Ion Reactions

    Horst Lenske · Jessica I.Bellone · Maria Colonna · Jose-Antonio Lay

    The theory of heavy ion single charge exchange reactions is reformulated. In momentum space the reaction amplitude factorizes into a product of projectile and target transition form factors, folded with the nucleon-nucleon isovector interaction and a distortion coefficient which accounts for initial and final state ion-ion elastic interactions. The multipole structure of the transition form factors is studied in detail for Fermi-type non-spin flip and Gamow-Teller-type spin flip transitions, also serving to establish the connection to nuclear beta decay. The reaction kernel is evaluated for central and rank-2 tensor interactions. Initial and final state elastic ion-ion interaction are shown to be dominated by the imaginary part of the optical potential allowing to evaluate the reaction coefficients in the strong absorption limit, realized by the black disk approximation. In that limit the distortion coefficient is evaluated in closed form, revealing the relation to the total reaction cross section and the geometry of the transition form factors. It is shown that at small momentum transfer distortion effects reduce to a simple scaling factor, allowing to define reduced forward-angle cross section which is given by nuclear matrix elements of beta decay-type. The response function formalism is used to describe nuclear charge changing transitions. Spectral distributions obtained by a self-consistent HFB and QRPA approach are discussed for excitations of and , respectively, and compared to spectroscopic data. The interplay of nuclear structure and reaction dynamics is illustrated for the single charge exchange reaction at MeV.

    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1803.06290 [pdf]
    PRC(2018)·64 citations
  6. 06

    [Submitted on 16 Mar 2018] (cross-list from hep-ph)

    Few-body quark dynamics for doubly-heavy baryons and tetraquarks

    Jean-Marc Richard (Lyon)🇫🇷 · Alfredo Valcarce (Salamanca)🇪🇸 · Javier Vijande (Valencia)🇪🇸

    We discuss the adequate treatment of the 3- and 4-body dynamics for the quark model picture of double-charm baryons and tetraquarks. We stress that the variational and Born-Oppenheimer approximations give energies very close to the exact ones, while the diquark approximation might be rather misleading. The Hall-Post inequalities also provide very useful lower bounds that exclude the possibility of stable tetraquarks for some mass ratios and some color wave functions.

    Comments:
    10 pages, 9 figures, to appear in Phys. Rev. C, one ref. added
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1803.06155 [pdf]
    PRC(2018)·90 citations
  7. 07

    [Submitted on 16 Mar 2018] (cross-list from hep-ph)

    On the MSW neutrino mixing effects in atomic weak interactions and double beta decays

    Mihai Horoi🇺🇸

    Matter effects on the mixing of the neutrinos mass eigenstates, also know as the Mikheyev-Smirnov-Wolfenstein effect, seem to be well established in describing the propagation of the neutrino from the source to detecting devices. These effects were mostly considered in bulk matter, but not inside the atoms. Here we consider the effect of the high electron densities existing in the atomic nuclei. We investigate if these effects can affect the known neutrino phenomenology. It was reported that the mixing of the neutrino in high density matter, such as inside a supernova, can affect the Majoron decay probabilities. We investigate if the neutrino mixing effects in the high electron density inside the atomic nuclei can change the neutrinoless double beta decay half-life formula. In both cases we found that the standard results stand. The results look simple, but the road to them is complex and it opens the possibility that the neutrino mixing in atomic nuclei may affect other observables, such as the neutrinoless double beta Majoron decays.

    Comments:
    8 pages, 4 figures
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1803.06332 [pdf]
    EPJA(2020)·3 citations

Affiliations

first authorsco-authorsvia INSPIRE