Exclusive Backward-Angle Omega Meson Electroproduction
[report]
Li Wenliang
2017
unpublished
Exclusive meson electroproduction at different squared four-momenta of the exchanged virtual photon, Q 2 , and at different four-momentum transfers, t and u, can be used to probe QCD's transition from hadronic degrees of freedom at the long distance scale to quark-gluon degrees of freedom at the short distance scale. Backward-angle meson electroproduction was previously ignored, but is anticipated to offer complimentary information to conventional forward-angle meson electroproduction studies
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... nucleon structure. This work is a pioneering study of backward-angle ω cross sections through the exclusive 1 H(e, e ′ p)ω reaction using the missing mass reconstruction technique. The extracted cross sections are separated into the transverse (T), longitudinal (L), and LT, TT interference terms. The analyzed data were part of experiment E01-004 (F π -2), which used 2.6-5.2 GeV electron beams and HMS+SOS spectrometers in Jefferson Lab Hall C. The primary objective was to detect coincidence π in the forward-angle, where the backward-angle ω events were fortuitously detected. The experiment has central Q 2 values of 1.60 and 2.45 GeV 2 , at W = 2.21 GeV. There was significant coverage in φ and ǫ, which allowed separation of σ T,L,LT,TT . The data set has a unique u coverage of −u ∼ 0, which corresponds to −t > 4 GeV 2 . The separated σ T result suggest a flat ∼ 1/Q 1.33±1.21 dependence, whereas σ L seems to hold a stronger 1/Q 9.43±6.28 dependence. The σ L /σ T ratio indicate σ T dominance at Q 2 = 2.45 GeV 2 at the ∼90% confidence level. After translating the results into the −t space of the published CLAS data, our data show evidence of a backward-angle ω electroproduction peak at both Q 2 settings. Previously, this phenomenon showing both forward and backward-angle peaks was only observed in the meson I would like to express my sincere gratitude to my supervisor Prof. Garth Huber for encouraging me to undertake this Ph.D. project and for his continuous support through the development of this work, and for his meticulous and patient guidance. Working with him has been a deeply educational and challenging experience. I also cherish the personal bond that we manage to create along these years. I am also very grateful to Henk Blok and Dave Gaskell for their extremely valuable suggestions, comments and supports during this work. A special thanks to Tanja Horn for her great work on generating data Ntuples, this has significantly simplified the analysis. Great appreciation to Jean-Phillipe Lansberg, Bernard Pire, Krill Semenov and Lech Szymanowski, for providing the invaluable theoretical (TDA model) calculations. Visions offered by Christian Weiss and Mark Strikman have played a critical role throughout the thesis writing. Furthermore, I want to thank the research funding provided by NSERC of Canada and the FGSR of the University of Regina. Since the beginning, Department of Physics has provided amazing supports for my education and research. I would like to thank all members of the department, include others. I am also grateful to all the friends and colleagues met at the university:
doi:10.2172/1408890
fatcat:uykhg2ldp5dkbknuakjo6sciba