270 research outputs found
The Low-Energy Theorem of Pion Photoproduction in Soliton Models of the Nucleon
We derive an analytic expression for the Kroll-Ruderman amplitude up to the
order 1/N_C for general Skyrme-type models of the nucleon. Due to the
degeneracy of intermediate N- and Delta-states we find deviations from the
standard low-energy theorem for the photoproduction of neutral pions.Comment: 17 pages, LATEX, SI-93-TP3S
Bag Formation in Quantum Hall Ferromagnets
Charged skyrmions or spin-textures in the quantum Hall ferromagnet at filling
factor nu=1 are reinvestigated using the Hartree-Fock method in the lowest
Landau level approximation. It is shown that the single Slater determinant with
the minimum energy in the unit charge sector is always of the hedgehog form. It
is observed that the magnetization vector's length deviates locally from unity,
i.e. a bag is formed which accommodates the excess charge. In terms of a
gradient expansion for extended spin-textures a novel O(3) type of effective
action is presented, which takes bag formation into account.Comment: 13 pages, 3 figure
Beyond CP violation: hadronic physics at BaBar
I report on recent studies of hadronic physics performed by the BaBar
Collaboration. Emphasis is given to the measurement of the properties of newly
discovered charmed hadrons and to the searches for light and heavy pentaquarks.Comment: 14 pages, 20 postscript figues, contributed to the Proceedings of the
First APS Topical Group Meeting on Hadron Physics, Fermilab, Batavia, IL
(October 24-26, 2004
The Casimir energy of skyrmions in the 2+1-dimensional O(3)-model
One-loop quantum corrections to the classical vortices in 2+1 dimensional
O(3)-models are evaluated. Skyrme and Zeeman potential terms are used to
stabilize the size of topological solitons. Contributions from zero modes,
bound-states and scattering phase-shifts are calculated for vortices with
winding index n=1 and n=2. For both cases the S-matrix shows a pronounced
series of resonances for magnon-vortex scattering in analogy to the
well-established baryon resonances in hadron physics, while vortices with n>2
are already classically unstable against decay. The quantum corrections
destabilize the classically bound n=2 configuration. Approximate independence
of the results with respect to changes in the renormalization scale is
demonstrated.Comment: 24 pages LaTeX, 14 figure
Strangeness, charm and bottom in a chiral quark-meson model
In this paper we investigate an SU(3) extension of the chiral quark-meson
model. The spectra of baryons with strangeness, charm and bottom are considered
within a "rigid oscillator" version of this model. The similarity between the
quark part of the Lagrangian in the model and the Wess-Zumino term in the
Skyrme model is noted. The binding energies of baryonic systems with baryon
number B=2 and 3 possessing strangeness or heavy flavor are estimated. The
results obtained are in good qualitative agreement with those obtained
previously in the topological soliton (Skyrme) model.Comment: 12 pages, no figures. Journal ref: submitted to Nucl.Phys.
Strange and Heavy Flavoured Hypernuclei in Chiral Soliton Models
The extention of the chiral soliton approach to hypernuclei - strange or
heavy flavoured - becomes more reliable due to success in describing of other
properties of nuclei, e.g. the symmetry energy of nuclei with atomic numbers up
to ~30. The binding energies of the ground states of light hypernuclei with
strangeness S=-1 have been described in qualitative agreement with data. The
existence of charmed or beautiful hypernuclei and Theta-hypernuclei (strange,
charmed or beautiful) with large binding energy is expected within same
approach.Comment: 5 pages, 4 figures. Talk given at the 9-th International Conference
on Hypernuclei and Strange Particle Physics (HYP2006), Mainz, Germany, 10-14
October 2006. Extended version "Baryon States in Chiral Soliton Models; from
Nuclei to Exotic Baryons" presented at the International Workshop "High
Energy Physics in the LHC Era", Universidad Tecnica Federico Santa Maria,
Valparaiso, Chile, 11-15 December 200
Flavored exotic multibaryons and hypernuclei in topological soliton models
The energies of baryon states with positive strangeness, or anti-charm
(-beauty) are estimated in chiral soliton approach, in the "rigid oscillator"
version of the bound state soliton model proposed by Klebanov and Westerberg.
Positive strangeness states can appear as relatively narrow nuclear levels
(Theta-hypernuclei), the states with heavy anti-flavors can be bound with
respect to strong interactions in the original Skyrme variant of the model (SK4
variant). The binding energies of anti-flavored states are estimated also in
the variant of the model with 6-th order term in chiral derivatives in the
lagrangian as solitons stabilizer (SK6 variant). The latter variant is less
attractive, and nuclear states with anti-charm or anti-beauty can be unstable
relative to strong interactions. The chances to get bound hypernuclei with
heavy antiflavors are greater within "nuclear variant" of the model with
rescaled model parameter (Skyrme constant e or e' decreased by ~30%) which is
expected to be valid for baryon numbers greater than B ~10. The rational map
approximation is used to describe multiskyrmions with baryon number up to ~30
and to calculate the quantities necessary for their quantization (moments of
inertia, sigma-term, etc.).Comment: 24 pages, 7 table
Dynamics of topological solitons in two-dimensional ferromagnets
Dynamical topological solitons are studied in classical two-dimensional
Heisenberg easy-axis ferromagnets. The properties of such solitons are treated
both analytically in the continuum limit and numerically by spin dynamics
simulations of the discrete system. Excitation of internal mode causes orbital
motion. This is confirmed by simulations.Comment: LaTeX, 15 pages, 6 figure
Resonances, and mechanisms of Theta-production
After explaining necessity of exotic hadrons, we discuss mechanisms which
could determine production of the exotic Theta-baryon. A possible important
role of resonances (producing the Theta in real or virtual decays) is
emphasized for various processes. Several experimental directions for studies
of such resonances, and the Theta itself, are suggested. We briefly discuss
also recent negative results on the Theta-baryon.Comment: 6 page
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