119064025
Point symmetries in the Hartree-Fock approach. I. Densities, shapes, and currents
Three mutually perpendicular symmetry axes of the second order, inversion, and time reversal can be used to construct a double point group denoted by D2h(TD). Properties of this group are analyzed in relation to the symmetry and symmetry-breaking effects within the mean-field (Hartree-Fock) theories, both in even and odd fermion systems. We enumerate space symmetries of local one-body densities, and symmetries of electromagnetic moments, that appear when some or all of the D2h(TD) elements represent self-consistent mean-field symmetries.
119356133
The Shears Mechanism in 142Gd in the Skyrme-Hartree-Fock Method with the Tilted-Axis Cranking
We report on the first Skyrme-Hartree-Fock calculations with the tilted-axis cranking in the context of magnetic rotation. The mean field symmetries, differences between phenomenological and self-consistent methods and the generation of shears-like structures in the mean field are discussed. Significant role of the time-odd spin-spin effective interaction is pointed out. We reproduce the shears mechanism, but quantitative agreement with experiment is rather poor. It may have to do with too large core polarization, lack of pairing correlations or properties of the Skyrme force.
23672287
Superdeformation in the quasicontinuum: Microscopic view of the excited superdeformed bands and the corresponding level densities.
Microscopic calculations of both the normal and the superdeformed rotational bands have been performed for a number of rare earth nuclei. The universal'' Woods-Saxon potential and the extended Strutinsky method have been used. Excited bands up to a prescribed energy limit {ital E}{sup *} (usually 2.5 to 3.5 MeV) have been calculated individually by minimizing the corresponding nuclear energies over the quadrupole and hexadecapole deformations. This turns out to be essential, when comparing with experimental results for the known discrete bands. An important influence of the superdeformed neutron ({ital N}=86) shell closure on the microscopically calculated rotational-level densities is illustrated and discussed.
16534405
Solution of the Skyrme—Hartree—Fock equations in the Cartesian deformed harmonic oscillator basis II. The program HFODD
Abstract We describe a method of solving the nuclear Skyrme-Hartree-Fock problem by using a deformed Cartesian harmonic oscillator basis. The complete list of expressions required to calculate local densities, total energy, and self-consistent fields is presented, and an implementation of the self-consistent symmetries is discussed. Formulas to calculate matrix elements in the Cartesian harmonic oscillator basis are derived for the nuclear and Coulomb interactions.
24677742
Critical frequency in nuclear chiral rotation.
Self-consistent solutions for the so-called planar and chiral rotational bands in 132La are obtained for the first time within the Skyrme-Hartree-Fock cranking approach. It is suggested that the chiral rotation cannot exist below a certain critical frequency which under the approximations used is estimated as Planck's omega(crit) approximately 0.5-0.6 MeV. However, the exact values of Planck's omega(crit) may vary, to an extent, depending on the microscopic model used, in particular, through the pairing correlations and/or calculated equilibrium deformations. The existence of the critical frequency is explained in terms of a simple classical model of two gyroscopes coupled to a triaxial rigid body.
119453196
Search for the Jacobi shape transition in light nuclei
Abstract.The $\gamma$-rays following the reaction 105 MeV 18O + 28Si have been measured using the EUROBALL IV, HECTOR and EUCLIDES arrays in order to investigate the predicted Jacobi shape transition. The high-energy $\gamma$-ray spectrum from the GDR decay indicates the presence of large deformations in the hot 46Ti nucleus, in agreement with new theoretical calculations based on the rotating liquid-drop model.
15493314
Pentaquark implications for exotic mesons
If the exotic baryon {theta}{sup +}(1540) is a correlated ududs with J{sup P}=(1{sup +}/2), then there should exist an exotic meson {theta}{sup +} with strangeness +2, J{sup P}=1{sup -}, mass {approx}1.6 GeV, decaying to K{sup +}K{sup 0} with width O(10-100) MeV. The {pi}{sub 1}(1400;1600) may be broad members of 10{+-}10 in such a picture, and it is possible that vector mesons in the 1.4-1.7 GeV mass range are related to this multiplet. We suggest that dynamical correlations may limit the spectrum of J{sup P(C)} such that the 1{sup -({+-}}{sup )} states are isolated.
117742301
Light-Meson Two-Photon Decays in Full QCD
We present a study of two-photon decays of light mesons, focusing on the neutral pion decay. This important process highlights the effects of the axial anomaly in QCD but has been little studied on the lattice. By applying the Lehmann-Symanzik-Zimmermann (LSZ) reduction formula, we reconstruct the electromagnetic matrix elements from three-point vector-vector Green functions calculated on 2+1-flavor isotropic clover lattices.
119265714
Helicity operators for mesons in flight on the lattice
Motivated by the desire to construct meson-meson operators of definite relative momentum in order to study resonances in lattice QCD, we present a set of single-meson interpolating fields at non-zero momentum that respect the reduced symmetry of a cubic lattice in a finite cubic volume. These operators follow from the subduction of operators of definite helicity into irreducible representations of the appropriate little groups. We show their effectiveness in explicit computations where we find that the spectrum of states interpolated by these operators is close to diagonal in helicity, admitting a description in terms of single-meson states of identified JPC. Lastly, the variationally determined optimal superpositions of the operators for each state give rapid relaxation in Euclidean time to that state, ideal for the construction of meson-meson operators and for the evaluation of matrix elements at finite momentum.
121740666
Baryon spectroscopy in lattice QCD with spin identification
Lattice QCD calculations are presented for the spectra of N* excited states with spins up to J = 7/2. The lattice operators and analysis methods used to identify the continuum spins in the lattice calculations are reviewed. In simulations with mπ ≥ 392 MeV, the low-lying excited states of lattice QCD are found to have the same quantum numbers as the states of SU(6) ⊗O(3) symmetry. The lattice spectra are inconsistent with either a quark-diquark model or parity doubling of states.
26774971
Electroweak production of hybrid mesons in a flux-tube simulation of lattice QCD.
We make the first calculation of the electroweak couplings of hybrid mesons to conventional mesons appropriate to photoproduction and to the decays of B or D mesons. E1 amplitudes are found to be large and may contribute in charge exchange gammap-->nH(+) allowing production of (among others) the charged 1(-+) exotic hybrid off a(2) exchange. Axial hybrid meson photoproduction is predicted to be large courtesy of pi exchange, and its strange hybrid counterpart is predicted in B-->psiK(H)(1(+)) with branching ratio B approximately 10(-4). Higher multipoles and some implications for hybrid charmonium are briefly discussed.