Beam Normal Single Spin Asymmetry in Forward Angle Inelastic Electron-Proton Scattering using the Q-Weak Apparatus
Beam Normal Single Spin Asymmetry in Forward Angle Inelastic Electron-Proton Scattering Using the Q-weak Apparatus. (December 2014) Nuruzzaman, M. S., Mississippi State University; M. Sc., Indian Institute of Technology Roorkee; B. Sc., University of Kalyani Chair of Advisory Committee: Liguang Tang The Q-weak experiment in Hall-C at the Thomas Jefferson National Accelerator Facility has made the first direct measurement of the weak charge of the proton through the precision measurement of the
... measurement of the parity-violating asymmetry in elastic electron-proton scattering at low momentum transfer. There is also a parity conserving Beam Normal Single Spin Asymmetry or transverse asymmetry (B n ) on H 2 with a sin(φ)-like dependence due to two-photon exchange. If the size of elastic B n is a few ppm, then a few percent residual transverse polarization in the beam, combined with small broken azimuthal symmetries in the detector, would require a few ppb correction to the Q-weak data. As part of a program of B n background studies, we made the first measurement of B n in the N-to-∆(1232) transition using the Q-weak apparatus. The final transverse asymmetry, corrected for backgrounds and beam polarization, was found to be B n = 42.82 ± 2.45 (stat) ± 16.07 (sys) ppm at beam energy E beam = 1.155 GeV, scattering angle θ = 8.3 • , and missing mass W = 1.2 GeV. B n from electron-nucleon scattering is a unique tool to study the γ * ∆∆ form factors, and this measurement will help to improve the theoretical models on beam normal single spin asymmetry and thereby our understanding of the doubly virtual Compton scattering process. To help correct false asymmetries from beam noise, a beam modulation system was implemented to induce small position, angle, and energy changes at the target to characterize detector response to the beam jitter. Two air-core dipoles separated by ∼10 m were pulsed at a time to produce position and angle changes at the target, for virtually any tune of the beamline. The beam energy was modulated using an SRF cavity. The hardware and associated control instrumentation will be described in this dissertation. Preliminary detector sensitivities were extracted which helped to reduce the width of the measured asymmetry. The beam modulation system has also proven valuable for tracking changes in the beamline optics, such as dispersion at the target. iv Dedicated to my parents Md. Shamsuzzoha, Nurun Nahar, my wife Shampa Samanta, my sister ACKNOWLEDGEMENTS This experiment was sponsored by the Department of Energy Office of Science (DOE), National Science Foundation (NSF), NSERC and the State of Virginia. I am very grateful for the support I received and the opportunities that were available during this time. I am indebted to a seemingly countless number of people for what I have accomplished. I would like to thank the individuals listed below. My supervisor, Liguang Tang, provided me with many opportunities and I am very grateful for his support through the entire process. When I first joined Hampton University (HU) graduate program, Dr. Tang welcomed me to his research group and explained all the opportunities I can have. He provided many interesting projects to work on, including the weak charge measurement of proton at Jefferson Lab. He encouraged me to attend several conferences during my time at HU, including those in American Physical Society Atlanta, California and Washington conferences. I feel very proud and fortunate to work with my Jefferson Lab supervisor Dave Mack. It was delight working with him. He helped me to understand the lab environment and equipment in many ways. We discussed different topics of experimental nuclear physics field regularly, which helped me to build my knowledge about the field. He always encouraged me to think about great ideas. His deep knowledge and understanding of the field also helped me to solve problems very quickly. I can not thank Dr. Dipangkar Dutta enough for his encouragement and help in my professional and personal life. My research career started at Mississippi State University (MSU) with Dr. Dutta. He introduced me to the Jefferson Lab (JLab) and allowed me to work in different projects with him as my advisor, including the nuclear transparency of kaons and weak charge measurement of the proton at Jefferson Lab.