32 research outputs found
Extended SAID Partial-Wave Analysis of Pion Photoproduction
A unified Chew-Mandelstam description of single-pion photoproduction data,
together with pion- and eta-hadroproduction data, has been extended to include
measurements carried out over the last decade. We consider photo-decay
amplitudes evaluated at the pole with particular emphasis on ng couplings and
the influence of weighting on our fits. Both energy-dependent and single-energy
analysis (energy-binned data) are considered.Comment: 30 pages, 18 figures, and 14 table
Singularity structure of the pi N scattering amplitude in a meson-exchange model up to energies W < 2.0 GeV
Within the previously developed Dubna-Mainz-Taipei meson-exchange model, the
singularity structure of the pi N scattering amplitudes has been investigated.
For all partial waves up to F waves and c.m. energies up to W = 2 GeV, the
T-matrix poles have been calculated by three different techniques: analytic
continuation into the complex energy plane, speed-plot and the regularization
method. For all 4-star resonances, we find a perfect agreement between the
analytic continuation and the regularization method. We also find resonance
poles for resonances that are not so well established, but in these cases the
pole positions and residues obtained by analytic continuation can substantially
differ from the results predicted by the speed-plot and regularization methods.Comment: 21 pages, 4 figures, 4 table
Geodetic Constraints on the 2014 M 6.0 South Napa Earthquake
On 24 August 2014, the M 6.0 South Napa earthquake shook much of the San Francisco Bay area, leading to significant damage in the Napa Valley. The earthquake occurred in the vicinity of the West Napa fault (122.313° W, 38.22° N, 11.3 km), a mapped structure located between the Rodger’s Creek and Green Valley faults, with nearly pure right‐lateral strike‐slip motion (strike 157°, dip 77°, rake –169°; http://comcat.cr.usgs.gov/earthquakes/eventpage/nc72282711#summary, last accessed December 2014) (Fig. 1). The West Napa fault previously experienced an M 5 strike‐slip event in 2000 but otherwise exhibited no previous definitive evidence of historic earthquake rupture (Rodgers et al., 2008; Wesling and Hanson, 2008). Evans et al. (2012) found slip rates of ∼9.5 mm/yr along the West Napa fault, with most slip rate models for the Bay area placing higher slip rates and greater earthquake potential on the Rodger’s Creek and Green Valley faults, respectively (e.g., Savage et al., 1999; d’Alessio et al., 2005; Funning et al., 2007)
Eta and Etaprime Photoproduction on the Nucleon with the Isobar Model EtaMAID2018
The isobar model EtaMAID has been updated with new and high precision data
for eta and etaprime photoproduction on protons and neutrons from MAMI, ELSA,
GRAAL and CLAS. The background is described in a recently developed Regge-cut
model, and for the resonance part the whole list of nucleon resonances has been
investigated with 21 N* states contributing to eta photoproduction and 12 N*
states contributing to etaprime photoproduction. A new approach is discussed to
avoid double counting in the overlap region of Regge and resonances. A
comparison is done among four newly updated partial waves analyses for
observables and partial waves. Finally, the possibility of a narrow resonance
near W=1900 MeV is discussed, that would be able to explain unexpected energy
and angular dependence of observables in p(gamma,etaprime)p near etaprime
threshold.Comment: 31 pages, 29 figures, replaced with revised versio
Beam-target helicity asymmetry for γ→n→→π−p in the N*resonance region
We report the first beam-target double-polarization asymmetries in the γ þ nðpÞ → π− þ pðpÞ reaction
spanning the nucleon resonance region from invariant mass W ¼ 1500 to 2300 MeV. Circularly polarized
photons and longitudinally polarized deuterons in solid hydrogen deuteride (HD) have been used with the
CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab. The exclusive final state has been
extracted using three very different analyses that show excellent agreement, and these have been used to
deduce the E polarization observable for an effective neutron target. These results have been incorporated
into new partial wave analyses and have led to significant revisions for several γnN* resonance
photocouplings
Beam-Target Helicity Asymmetry for γ (over-right-arrow) n (over-right-arrow) → π − p in the N* Resonance Region
We report the first beam-target double-polarization asymmetries in the γ þ nðpÞ → π− þ pðpÞ reaction
spanning the nucleon resonance region from invariant mass W ¼ 1500 to 2300 MeV. Circularly polarized
photons and longitudinally polarized deuterons in solid hydrogen deuteride (HD) have been used with the
CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab. The exclusive final state has been
extracted using three very different analyses that show excellent agreement, and these have been used to
deduce the E polarization observable for an effective neutron target. These results have been incorporated
into new partial wave analyses and have led to significant revisions for several γnN* resonance
photocouplings