9,734 research outputs found
Study of unstable particle through the spectral function in O(4) theory
We test application of the maximum entropy method to decompose the states
contributing to the unstable correlation function through the spectral
function in the four dimensional O(4) theory. Reliable results are
obtained for the mass and two-particle state energy using
only the correlation function. We also find that the property of the
particle is different between the unstable ()
and stable () cases.Comment: Lattice2002(spectrum), 3 page
Nuclear Quadrupole Effects in Deeply Bound Pionic Atoms
We have studied nuclear quadrupole deformation effects in deeply bound pionic
atoms theoretically. We have evaluated the level shifts and widths of the
hyperfine components using the first order perturbation theory and compared
them with the effects of neutron skin. We conclude that the nuclear quadrupole
deformation effects for deeply bound and states are very difficult to
observe and that the effects could be observed for states. We also
conclude that the deformation effects are sensitive to the parameters of the
pion-nucleus optical potential.Comment: Latex 11pages, Figures available on reques
Realistic calculations of Kbar-N-N, Kbar-N-N-N, and Kbar-Kbar-N-N quasibound states
Binding energies and widths of three-body KbarNN, and of four-body KbarNNN
and KbarKbarNN nuclear quasibound states are calculated in the hyperspherical
basis, using realistic NN potentials and subthreshold energy dependent chiral
KbarN interactions. Results of previous K^-pp calculations are reproduced and
an upper bound is placed on the binding energy of a K^-d quasibound state. A
self consistent handling of energy dependence is found to restrain binding,
keeping the calculated four-body ground-state binding energies to relatively
low values of about 30 MeV. The lightest strangeness -2 particle-stable Kbar
nuclear cluster is most probably KbarKbarNN. The calculated Kbar N -> pi Y
conversion widths range from approximately 30 MeV for the KbarNNN ground state
to approximately 80 MeV for the KbarKbarNN ground state.Comment: v3 matching journal publicatio
Theoretical Response to the Discovery of Deeply Bound Pionic States in 208Pb(d,3He) reactions
Recently, deeply bound pionic states were found experimentally in (d, He)
reactions on Pb. They found an isolated peak structure in the bound
region below the pion production threshold. We study theoretically these
excitation functions in (d, He) reactions on Pb at T=600 MeV.
We found very good agreement with the (d, He) excitation functions and
could identify the underlying structures of the pionic states. We study the
energy dependence of the (d, He) reactions and the change of the excitation
functions with the incident energy.Comment: 5 pages, Latex, Figures available on request, Z.Phys.A.accepte
QUAGMIRE v1.3: a quasi-geostrophic model for investigating rotating fluids experiments
QUAGMIRE is a quasi-geostrophic numerical model for performing fast, high-resolution simulations of multi-layer rotating annulus laboratory experiments on a desktop personal computer. The model uses a hybrid finite-difference/spectral approach to numerically integrate the coupled nonlinear partial differential equations of motion in cylindrical geometry in each layer. Version 1.3 implements the special case of two fluid layers of equal resting depths. The flow is forced either by a differentially rotating lid, or by relaxation to specified streamfunction or potential vorticity fields, or both. Dissipation is achieved through Ekman layer pumping and suction at the horizontal boundaries, including the internal interface. The effects of weak interfacial tension are included, as well as the linear topographic beta-effect and the quadratic centripetal beta-effect. Stochastic forcing may optionally be activated, to represent approximately the effects of random unresolved features. A leapfrog time stepping scheme is used, with a Robert filter. Flows simulated by the model agree well with those observed in the corresponding laboratory experiments
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