Measurement of Hard Exclusive Electroproduction of π⁰ Meson Cross Section in Hall A of JLab with CEBAF at 12 GeV

Thesis/Dissertation · Sun Dec 01 04:00:00 EST 2019

DOI:https://doi.org/10.2172/1574097· OSTI ID:1574097

Dlamini, Mongi ^[1]

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1. Ohio Univ., Athens, OH (United States)

A complete description of nucleon structure requires the simultaneous knowledge of both the spatial and momentum information of the ultimate constituents of the nucleon, the quarks and gluons. Generalized Parton Distributions (GPDs) provide such tools to describe nucleon structure. GPDs are measurable through hard exclusive processes like Deeply Virtual Compton Scattering (DVCS) and Deeply Virtual Meson Production (DVMP). GPDs can describe hard exclusive processes only if Bjorken factorization is achieved during the hard scattering process. While DVCS data have given hints of the factorization regime being attained, such hints have not been observed for DVMP data. Testing for factorization in DVMP processes is the topic of this thesis. Exclusive π⁰ electroproduction has been measured by experiment E12-06-114 in Hall A of JLab. Cross sections have been measured at three fixed Bjorken-x (x_B): 0.35, 0.48 and 0.6 in the Q² range 3 to 9 GeV². In this document we present an analysis of a subset of the data: x_B = 0.35 in the Q² range 3.1 to 4.5 GeV². The different structure functions: unseparated cross section (σ_T + ϵσ_L), longitudinal-transverse interference (σ_LT), transverse-transverse interference (σ_TT), and the polarized response (σ_LT') terms were extracted. The data was compared to a transversity GPD model. The model fails to reproduce the data even though the order of magnitude is in agreement for both model and data. We observe a strong disagreement between the data and the model for σ_LT in terms of both magnitude and the cross section sign. Our results are in a larger and wider Q² domain but they are in agreement with existing measurements.

• Research Organization: Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26)
• DOE Contract Number: AC05-06OR23177
• OSTI ID: 1574097
• Report Number(s): JLAB-PHY-19-3095; DOE/OR/23177-4810
• Country of Publication: United States
• Language: English