28 research outputs found
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
Co-Seismic Displacements of the 1992 Landers Earthquake Sequence
We present co-seismic displacement vectors derived from Global Positioning System (GPS) measurements of 92 stations in southern California. These GPS results are combined with five well-determined GPS displacement vectors from continuously tracking stations of the Permanent GPS Geodetic Array, as well as line-length changes from USGS Geodolite and two-color laser trilateration observations, to determine a self-consistent set of geodetic data for the earthquake. These combined displacements are modeled by an elastic dislocation representation of the primary fault rupture planes. On average, the model residuals are about twice the estimated measurement errors
Differential Cross Section Measurements for γn→π-p Above the First Nucleon Resonance Region
The quasifree γd→π-p(p) differential cross section has been measured with CLAS at photon beam energies Eγ from 0.445 to 2.510 GeV (corresponding to W from 1.311 to 2.366 GeV) for pion center-of-mass angles cosθπc.m. from -0.72 to 0.92. A correction for final state interactions has been applied to these data to extract the γn→π-p differential cross sections. These cross sections are quoted in 8428 (Eγ,cosθπc.m.) bins, a factor of nearly 3 increase in the world statistics for this channel in this kinematic range. These new data help to constrain coupled-channel analysis fits used to disentangle the spectrum of N∗ resonances and extract their properties. Selected photon decay amplitudes N∗→γn at the resonance poles are determined for the first time and are reported here. © 2017 American Physical Society
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