First measurement of F double polarisation observable in pion photoproduction

Abstract

The composite structure of the nucleon leads to a spectrum of excited states, or resonances, which contain important constraints on the dynamics and interactions of its constituents. A major world programme measuring meson photoproduction from the nucleon is currently under way to improve our knowledge of this fundamental spectrum. These new generation of measurements exploit polarisation degrees of freedom of the incident photon along with spin degrees of freedom in the target and recoiling nucleons. The meson photoproduction process can be described by 16 independent experimental observables. To fully constrain the four underlying complex photoproduction amplitudes requires the measurement of a least 8 of these. Measurements of double polarisation observables, where the photon beam and nucleon target are polarised are crucial to achieve this requirement. This thesis will present the analysis and extraction of the first preliminary measurement of the double polarisation observable. F in the single pion photoproduction reaction γ→ + p →n + π+ was undertaken to measure both F and T. The resulting measurement of polarisation observables from this reaction in conjunction with with those from the Pπ0 channel will provide stringent constraints on partial wave analyses aiming to extract precision information on the properties of the low lying nucleon resonances.