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The Differential Cross Section and Λ Recoil Polarization from γδ -> Κ0(ρ) [report]

Nicholas Compton
2017 unpublished
Presented is the analysis of the differential cross section and Λ recoil polarization from the reaction γd → K 0 Λ(p). This work measured these observables over beam energies from 0.90 GeV to 3.0 GeV. These measurements are the first in this channel to cover such a wide range of energies. The data were taken using the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Laboratory (JLAB) along with a tagged photon beam. This analysis was completed by identifying events of interest that
more » ... interest that decayed into the final state topology of π − π + π − p(p). Through conservation of energy and momentum, the K 0 , Λ, and missing mass of the spectator proton were reconstructed. Utilizing the same analysis techniques, the observables were measured on two different experiments with good agreement. Photoproduction of strange mesons from the neutron are difficult to measure, consequently there are only a few measurements of this kind. Despite that, these reactions supply essential complementary data to those on the proton. The differential cross sections and the recoil polarization extracted, span the region where new nucleon resonances have been found from studies of the reaction γp → K + Λ. Comparisons between the K + Λ and K 0 Λ cross section demonstrate that possible interference terms near 1900 MeV are less pronounced in the latter. This unexpected result inspired a partial wave analyses (PWA) to be fitted to the data. The fit solution shows that this measurement fostered an improvement on the knowledge of observed resonance parameters, necessary to understanding these excited states. The study of nucleon resonances is a key motivating factor since the resonance masses can be calculated from the theory of the strong nuclear force, called quantum chromodynamics, or QCD.
doi:10.2172/1427017 fatcat:mfasqjveirdllppdaropxhixze