27 research outputs found
Hyperon resonances in radiative kaon capture
We use crossing symmetry to extend our Regge model for electromagnetic
kaon production from the proton to the case of radiative kaon capture. Our model is based on the exchange of the K(494) and K*(892) Regge trajectories in the t-channel. We use the parameters fitted to describe the p(gamma,K+)Y reaction to make predictions for the p(K-,gamma)Y process. The differential cross sections of the latter for kaon momenta of 520 and 750 MeV/c show a satisfactory agreement with data from the Crystal Ball Collaboration
Regge-plus-resonance predictions for kaon photoproduction from the neutron
We present predictions for n(gamma,K+)Sigma- differential cross sections and
photon-beam asymmetries and compare them to recent LEPS data. We adapt a
Regge-plus-resonance (RPR) model developed to describe photoinduced and
electroinduced kaon production off protons. The non-resonant contributions to
the amplitude are modelled in terms of K+(494) and K*+(892) Regge-trajectory
exchange. This amplitude is supplemented with a selection of s-channel
resonance diagrams. The three Regge-model parameters of the n(gamma,K+)Sigma-
amplitude are derived from the ones fitted to proton data through SU(2) isospin
considerations. A fair description of the n(gamma,K+)Sigma- data is realized,
which demonstrates the Regge model's robustness and predictive power.
Conversion of the resonances' couplings from the proton to the neutron is more
challenging, as it requires knowledge of the photocoupling helicity amplitudes.
We illustrate how the uncertainties of the helicity amplitudes propagate and
heavily restrain the predictive power of the RPR and isobar models for kaon
production off neutron targets.Comment: 14 pages, 4 figures; Minor revisions; Published in Physics Letters
Regge-plus-resonance predictions for charged-kaon photoproduction from the deuteron
We present a Regge-inspired effective-Lagrangian framework for charged-kaon
photoproduction from the deuteron. Quasi-free kaon production is investigated
using the Regge-plus-resonance elementary operator within the non-relativistic
plane-wave impulse approximation. The Regge-plus-resonance model was developed
to describe photoinduced and electroinduced kaon production off protons and can
be extended to strangeness production off neutrons. The non-resonant
contributions to the amplitude are modelled in terms of K+(494) and K*+(892)
Regge-trajectory exchange in the t-channel. This amplitude is supplemented with
a selection of s-channel resonance-exchange diagrams. We investigate several
sources of theoretical uncertainties on the semi-inclusive charged-kaon
production cross section. The experimental error bars on the photocoupling
helicity amplitudes turn out to put severe limits on the predictive power when
considering quasi-free kaon production on a bound neutron.Comment: 5 pages, 2 figures; Proceedings 19th International IUPAP Conference
on Few-Body Problems in Physics, Bonn, 200
Mapping chiral symmetry breaking in the excited baryon spectrum
We study the conjectured "Insensitivity to Chiral Symmetry Breaking" in the
highly excited light baryon spectrum. While the experimental spectrum is being
measured at JLab and CBELSA/TAPS, this insensitivity remains to be computed
theoretically in detail. As the only existing option to have both confinement,
highly excited states and chiral symmetry, we adopt the truncated Coulomb gauge
formulation of QCD, considering a linearly confining Coulomb term. Adopting a
systematic and numerically intensive variational treatment up to 12 harmonic
oscillator shells we are able to access several angular and radial excitations.
We compute both the excited spectra of and baryons, up to large
spin , and study in detail the proposed chiral multiplets. While the
static-light and light-light spectra clearly show chiral symmetry restoration
high in the spectrum, the realization of chiral symmetry is more complicated in
the baryon spectrum than earlier expected.Comment: 22 pages, 16 figures, submitted to Phys. Rev.
Excited baryons as experimental probes of the quark mass
We observe that excited hadrons provide an opportunity to probe from
experiment the power-law running of the quark mass in the mid infrared, while
the condition m(k)<k remains valid. A relatively clean analysis is possible for
the maximum spin excitations of the Delta baryons, analogous to the yrast
states in nuclei. Such states are accessible at current experimental facilities
such as ELSA and Jlab.Comment: 6 pages, 2 figures, proceedings of ExcitedQCD, Zakopane, Poland