20,238 research outputs found
Nuclear shape coexistence in Po isotopes: An interacting boson model study
Background: The lead region, Po, Pb, Hg, and Pt, shows up the presence of
coexisting structures having different deformation and corresponding to
different particle-hole configurations in the Shell Model language.
Purpose: We intend to study the importance of configuration mixing in the
understanding of the nuclear structure of even-even Po isotopes, where the
shape coexistence phenomena are not clear enough.
Method: We study in detail a long chain of polonium isotopes, 190-208Po,
using the interacting boson model with configuration mixing (IBM-CM). We fix
the parameters of the Hamiltonians through a least-squares fit to the known
energies and absolute B(E2) transition rates of states up to 3 MeV.
Results: We obtained the IBM-CM Hamiltonians and we calculate excitation
energies, B(E2)'s, electric quadrupole moments, nuclear radii and isotopic
shifts, quadrupole shape invariants, wave functions, and deformations.
Conclusions: We obtain a good agreement with the experimental data for all
the studied observables and we conclude that shape coexistence phenomenon is
hidden in Po isotopes, very much as in the case of the Pt isotopes.Comment: To be published in Physical Review C. arXiv admin note: text overlap
with arXiv:1312.459
The influence of intruder states in even-even Po isotopes
We study the role of intruder states and shape coexistence in the even-even
Po isotopes, through an interacting boson model with configuration
mixing calculation. We analyzed the results in the light of known systematics
on various observable in the Pb region, paying special attention to the
unperturbed energy systematics and quadrupole deformation. We find that shape
coexistence in the Po isotopes behaves in very much the same way as in the Pt
isotopes, i.e., it is somehow hidden, contrary to the situation in the Pb and
the Hg isotopes.Comment: Contribution to the Nuclear Structure and Dynamics 2015 (Portorose,
Slovenia) proceeding
Short distance singularities and automatic O() improvement: the cases of the chiral condensate and the topological susceptibility
Short-distance singularities in lattice correlators can modify their Symanzik
expansion by leading to additional O() lattice artifacts. At the example of
the chiral condensate and the topological susceptibility, we show how to
account for these lattice artifacts for Wilson twisted mass fermions and show
that the property of automatic O() improvement is preserved at maximal
twist.Comment: 12 pages, corrected proof for topological susceptibility, version
published in JHE
Topological susceptibility from twisted mass fermions using spectral projectors
We discuss the computation of the topological susceptibility using the method
of spectral projectors and dynamical twisted mass fermions. We present our
analysis concerning the O(a)-improvement of the topological susceptibility and
we show numerical results for Nf=2 and Nf=2+1+1 flavours, performing a study of
the quark mass dependence in terms of leading order chiral perturbation theory.Comment: 7 pages, 3 figures; presented at the 31st International Symposium on
Lattice Field Theory (Lattice 2013), 29 July - 3 August 2013, Mainz, German
Non-localities and Fermi motion corrections in atoms
We evaluate the p-wave amplitudes from the chiral Lagrangians and from
there construct the p-wave part of the nucleus optical potential plus a
small s-wave part induced from the elementary p-wave amplitude and the nuclear
Fermi motion. Simultaneously, the momentum and energy dependence of the s-wave
optical potential, previously developed, are taken into account and shown to
generate a small p-wave correction to the optical potential. All the
corrections considered are small compared to the leading s-wave potential, and
lead to changes in the shifts and widths which are smaller than the
experimental errors.
A thorough study of the threshold region and low densities is conducted,
revealing mathematical problems for which a physical solution is given.Comment: revised version, 28 pages, Latex, 8 postscript figures. Submitted to
Nucl. Phys.
Partial dynamical symmetry as a selection criterion for many-body interactions
We propose the use of partial dynamical symmetry (PDS) as a selection
criterion for higher-order terms in situations when a prescribed symmetry is
obeyed by some states and is strongly broken in others. The procedure is
demonstrated in a first systematic classification of many-body interactions
with SU(3) PDS that can improve the description of deformed nuclei. As an
example, the triaxial features of the nucleus 156Gd are analyzed.Comment: 5 pages, 3 figures, Phys. Rev. C, in pres
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