30,182 research outputs found
On the nature of the Lambda(1405) as a superposition of two states
We use recent data on the reaction with the
mass distribution of forming the with a peak
at 1420 MeV and a relatively narrow width of MeV, together with
those of the reaction to show that there are two
states instead of one as so far assumed.Comment: Contribution to the PANIC05 Conference, Santa Fe, October 200
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
Disentangling the nuclear shape coexistence in even-even Hg isotopes using the interacting boson model
We intend to provide a consistent description of the even-even Hg isotopes,
172-200Hg, using the interacting boson model including configuration mixing. We
pay special attention to the description of the shape of the nuclei and to its
connection with the shape coexistence phenomenon.Comment: To appear in CGS15 conference proceedings (EPJ Web of Conferences
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
Note on the space group selection rule for closed strings on orbifolds
It is well-known that the space group selection rule constrains the
interactions of closed strings on orbifolds. For some examples, this rule has
been described by an effective Abelian symmetry that combines with a
permutation symmetry to a non-Abelian flavor symmetry like or
. However, the general case of the effective Abelian symmetries was
not yet fully understood. In this work, we formalize the computation of the
Abelian symmetry that results from the space group selection rule by imposing
two conditions only: (i) well-defined discrete charges and (ii) their
conservation. The resulting symmetry, which we call the space group flavor
symmetry , is uniquely specified by the Abelianization of the space group.
For all Abelian orbifolds with supersymmetry we compute and
identify new cases, for example, where contains a dark
matter-parity with charges 0 and 1 for massless and massive strings,
respectively.Comment: 28 pages, 1 tabl
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