250 research outputs found
Dynamical coupled-channels: the key to understanding resonances
Recent developments on a dynamical coupled-channels model of hadronic and
electromagnetic production of nucleon resonances are summarized.Comment: Invited Plenary talk at the 20th European Conference on Few-Body
Problems in Physics (EFB20), September 10-14 2007, Pisa, Italy. To appear in
the proceedings in Few-Body System
The role of components in the nucleon and the N(1440) resonance
The role of components in the nucleon and the N(1440) resonance is
studied by explicit coupling of the lowest positive parity state
to the components in the harmonic oscillator quark model. The lowest
energy component, where the 4-quark subsystem has the flavor-spin
symmetry , is close in energy to the lowest positive
parity excitation of the nucleon in the quark model. The confining
interaction leads to a strong mixing of the system and the
positive parity excited state of the system. This result is in line with
the phenomenological indications for a two-component structure of the N(1440)
resonance. The presence of substantial components in the N(1440) can
bring about a reconciliation of the constituent quark model with the large
empirical decay width of the N(1440).Comment: Accepted for publication in Nucl. Phys.
A microscopic NN to NN*(1440) potential
By means of a NN to NN*(1440) transition potential derived in a
parameter-free way from a quark-model based NN potential, we determine
simultaneously the and coupling constants.
We also present a study of the target Roper excitation diagram contributing to
the reaction.Comment: Talk presented at the Fourth International Conference on Perspectives
in Hadronic Physics (ICTP, Trieste, Italy, May 2003). To appear in EPJA. 6
pages, 9 figures, needs svepj.clo and svjour.cl
Saturation properties of helium drops from a Leading Order description
Saturation properties are directly linked to the short-range scale of the
two-body interaction of the particles. The case of helium is particular, from
one hand the two-body potential has a strong repulsion at short distances. On
the other hand, the extremely weak binding of the helium dimer locates this
system very close to the unitary limit allowing for a description based on an
effective theory. At leading order of this theory a two- and a three-body term
appear, each one characterized by a low energy constant. In a potential model
this description corresponds to a soft potential model with a two-body term
purely attractive plus a three-body term purely repulsive constructed to
describe the dimer and trimer binding energies. Here we analyse the capability
of this model to describe the saturation properties making a direct link
between the low energy scale and the short-range correlations. We will show
that the energy per particle, , can be obtained with reasonable accuracy
at leading order extending the validity of this approximation, characterizing
universal behavior in few-boson systems close to the unitary limit, to the
many-body system.Comment: 5 pages, 3 figure
Fast generation of spin-squeezed states in bosonic Josephson junctions
We describe methods for fast production of highly coherent-spin-squeezed
many-body states in bosonic Josephson junctions (BJJs). We start from the known
mapping of the two-site Bose-Hubbard (BH) Hamiltonian to that of a single
effective particle evolving according to a Schr\"odinger-like equation in Fock
space. Since, for repulsive interactions, the effective potential in Fock space
is nearly parabolic, we extend recently derived protocols for shortcuts to
adiabatic evolution in harmonic potentials to the many-body BH Hamiltonian. The
best scaling of the squeezing parameter for large number of atoms N is \xi^2_S
~ 1/N.Comment: Improved and enlarged version, accepted at Phys. Rev.
Single photo and electroproduction of pions at EBAC@JLAB
Within the Excited Baryon Analysis Center we have performed a dynamical
coupled-channels analysis of the available data in the region of
1.6 GeV and 1.45 (GeV/c). The channels included are
, , , and which has , , and components. With the hadronic parameters of the model
determined in our previous investigations of reaction, we have
found that the available data in the considered 1.6 GeV region can be
fitted well by only adjusting the bare helicity amplitudes
for the lowest states in , , and
partial waves. The meson cloud effect, as required by the unitarity conditions,
on the form factors are examined.Comment: 6 pages, invited talk at NSTAR 2009, Beijing (China), 2009, to appear
in the proceeding
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