First investigation of electromagnetic coupling of the d*(2380) hexaquark
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Date
29/11/2018Author
Kay, Stephen John Donald
Metadata
Abstract
This thesis presents the first measurement of the d*(2380) (hexaquark) electromagnetic
coupling, extracted from the deuteron photodisintegration (~γd → d* →~np) reaction. The experiment was carried out at the Mainzer Microtron
(MAMI) facility in the Institut für Kernphysik in Mainz, Germany. A racetrack
microtron at the MAMI facility provided a 1557 MeV longitudinally polarised
electron beam. This electron beam was directed onto a thin radiator to produce
a bremsstrahlung photon beam. Diamond and amorphous (metallic) radiators
were used to produce linearly and circularly polarised photons respectively. The
produced bremsstrahlung photon beam was energy 'tagged' with a resolution
of ~4 MeV over the photon-energy range of 150-1400 MeV using the Glasgow
Photon Tagger. The tagged photons were incident on a 10 cm long liquid
deuterium target. This target was surrounded by a new nucleon recoil polarimeter
apparatus and placed within the Crystal Ball calorimeter at MAMI. An array of
PbWO4 and BaF2 detectors (TAPS) was used to provide calorimetry at forward
angles.
The newly constructed large acceptance recoil polarimeter measures the polarisation
of the nucleons in the final state. The combination of this new
apparatus with the polarised photon beam facility gives access to a number of
single and double polarisation observables. The photon beam asymmetry, Ʃ,
and the double polarisation observable, Cx' , were examined in measurements of
the reaction d(→γ,→n→p) over a large range of energies with a close to full angular
coverage. The observable Cx' is determined for the neutron produced in deuteron
photodisintegration for the first time. The new data constrains mechanisms of
deuteron photodisintegration and assesses the existence and contribution of the
d*(2380) resonance.