125 research outputs found
Model-independent resonance parameter extraction using the trace of K and T matrices
A model-independent method for the determination of Breit-Wigner resonance
parameters is presented. The method is based on eliminating the dependence on
the choice of channel basis by analyzing the trace of the K and T matrices in
the coupled-channel formalism, rather than individual matrix elements of the
multichannel scattering matrix.Comment: 6 pages, 16 figure
A mass formula for baryon resonances
Light-baryon resonances with u,d, and s quarks only can be classified using
the non-relativistic quark model. When we assign to baryon resonances with
total angular momenta J intrinsic orbital angular momenta L and spin S we make
the following observations: plotting the squared masses of the light-baryon
resonances against these intrinsic orbital angular momenta L, Delta's with even
and odd parity can be described by the same Regge trajectory. For a given L,
nucleon resonances with spin S=3/2 are approximately degenerate in mass with
Delta resonances of same total orbital momentum L. To which total angular
momentum L and S couple has no significant impact on the baryon mass. Nucleons
with spin 1/2 are shifted in mass; the shift is - in units of squared masses -
proportional to the component in the wave function which is antisymmetric in
spin and flavor. Sequential resonances in the same partial wave are separated
in mass square by the same spacing as observed in orbital angular momentum
excitations. Based on these observations, a new baryon mass formula is proposed
which reproduces nearly all known baryon masses.Comment: 4 pages, 1 figur
In-medium broadening of nucleon resonances
We analyze the effects of an in-medium broadening of nucleon resonances on
the exclusive photoproduction of mesons on nuclei as well as on the total
photoabsorption cross sections in a transport calculation. We show that the
resonance widths observed in semi-inclusive photoproduction on nuclei are
insensitive to an in-medium broadening of nucleon resonances. This is due to a
simple effect: the sizeable width of the nuclear surface and Fermi motion.Comment: 4 pages, 3 figures, minor changes in the tex
P-A Measurements in the 48-Ca(p,n)48-Sc Reaction at 135 MeV
This research was sponsored by the National Science Foundation Grant NSF PHY-931478
Incoherent Photoproduction of -mesons from the Deuteron near Threshold
Incoherent photoproduction of the -meson on the deuteron is studied for
photon energies from threshold to 800 MeV. The dominant contribution, the
N-N amplitude, is described within an isobar model. The final
state interaction derived from the CD-Bonn potential is included and found to
be important for the description of the production cross section close to
threshold. Possible effects from the final state interaction are
discussed.Comment: 11 pages, revtex, including 6 figure
Fragmentation of High-spin Stretched States in the (p,n) Reaction on 36-Ar and 40-Ca
This research was sponsored by the National Science Foundation Grant NSF PHY-931478
Search for a State at E_x = 2.6MeV in 20-Na via the 20-Ne(p,n)20-Na Reaction and Possible Breakout from the Hot CNO Cycle
This research was sponsored by the National Science Foundation Grant NSF PHY-931478
Quasi-Two-Body Decays of Nonstrange Baryons
We examine the decays of nonstrange baryons to the final states ,
, , , , , and
, in a relativized pair-creation() model which has
been developed in a previous study of the decays of the same baryon
states. As it is our goal to provide a guide for the possible discovery of new
baryon states at CEBAF and elsewhere, we examine the decays of resonances which
have already been seen in the partial-wave analyses, along with those of states
which are predicted by the quark model but which remain undiscovered. The level
of agreement between our calculation and the available widths from the
partial-wave analyses is encouraging.Comment: 41 pages, CEBAF-TH-93-1
High-Spin Stretched States in Nuclei Excited via (p,n) Reactions
This research was sponsored by the National Science Foundation Grant NSF PHY 87-1440
Delta rho pi interaction leading to N* and Delta* resonances
We have performed a calculation for the three body system
by using the fixed center approximation to Faddeev equations, taking the
interaction between and , and, and and
from the chiral unitary approach. We find several peaks in the modulus
squared of the three-body scattering amplitude, indicating the existence of
resonances, which can be associated to known and and baryon states.Comment: Presented at the 21st European Conference on Few-Body Problems in
Physics, Salamanca, Spain, 30 August - 3 September 201
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