Beam-, Target- and Double- Spin Asymmetry Measurements in Deeply Virtual π⁰, π⁺ and π^- Meson Production

Thesis/Dissertation · Fri Mar 01 00:00:00 EST 2019

DOI:https://doi.org/10.2172/1574096· OSTI ID:1574096

Murdoch, Gavin ^[1]

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1. Univ. of Glasgow, Scotland (United Kingdom)

This thesis presents measurements of spin asymmetries in single pion electroproduction from the EG1-DVCS experiment carried out at the Thomas Jefferson National Accelerator Facility in 2009 with use of the CEBAF Large Acceptance Spectrometer. The experiment made use of a 6 GeV longitudinally polarised electron beam and (dynamically) longitudinally polarised targets of ¹⁴NH₃ and ¹⁴ND₃ (giving access to protons and deuterons), providing the means to measure three spin asymmetries: beam-, target-, and double-spin. Deeply Virtual Meson Production for the π⁰, π⁺ and π^- channels were studied for the kinematic range of Q² > 1 GeV² and W > 2 GeV. The collection of measurements includes the analysis of numerous reconstruction topologies, as well as making use of different target materials. These are the world's first charged pion spin asymmetry measurements in this kinematic regime. The sPlot maximum likelihood fit based background subtraction technique was implemented in the data analysis, showing strong agreement with a traditional and commonly used cuts-based approach. This novel technique was thoroughly tested to develop implementation and execution. The results obtained will provide a reference point for future analyses at the upgraded experimental facility and motivate the use of the sPlot technique. These measurements will provide insight into the structure of nucleons through their interpretation in relation to Generalised Parton Distributions which describe substructure correlations between longitudinal momentum and transverse position of partons. In particular, here the spin asymmetries dependence on t, the squared four-momentum transfer to the target nucleon, carries information on the spatial parton distributions in the transverse plane.

• Research Organization: Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Nuclear Physics (NP)
• DOE Contract Number: AC05-06OR23177
• OSTI ID: 1574096
• Report Number(s): JLAB-THY-19-3096; DOE/OR/23177-4809
• Country of Publication: United States
• Language: English