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[PAST EVENT] Melissa A. Cummings, Physics - Oral Exam for the Ph.D.
December 18, 2015
10am - 1pm
Abstract:
Although the proton is a primary constituent of all visible matter in the universe, it is not fundamental in the same way as the point-like electron; rather, it is a complex system composed of quarks and gluons exhibiting many-body interactions. Electron scattering, where a high-energy electron scatters off a proton target, is a powerful probe in studying the internal structure of proton. If the electron and proton in this process are polarized they provide additional degrees of freedom to study the spin structure of the proton. The scattering cross-section of such processes can be parameterized by four structure functions, which can be obtained using different configurations of an unpolarized or polarized proton target. The fourth structure function, g2, describes the spin-dependent behavior of a proton when it is polarized transversely with respect to the electron polarization. While the other three structure functions have been measured over a wide range of kinematics, due to the experimental difficulty of measuring it, data for g2 remains scarce. The g2p Experiment, which ran in Experimental Hall A at Thomas Jefferson National Lab, will provide the first measurement of g2 for the proton at low momentum transfer (0.02 < Q2 < 0.2 GeV2) in the resonance region. These data will provide insight to several physics puzzles, such as why effective field theories fail to predict spin-dependent properties of the nucleon, specifically the proton polarizabilities. This talk will outline the theory and motivation behind the g2p experiment as well as present the current status of the analysis.
Bio:
Melissa Cummings is a native of Palmyra, NY. She graduated from the State University of NY at Geneseo in 2009 with a B.A. in Physics. She began her graduate studies at William & Mary in the fall of the same year, where she started working with Dr. Todd Averett. Her research has been focused on the g2p experiment at Jefferson Lab, which will provide the first measurement of the proton spin structure function g2 at low momentum transfer. After graduating, Melissa will begin working at the Institute for Defense Analyses in Alexandria, VA.
Although the proton is a primary constituent of all visible matter in the universe, it is not fundamental in the same way as the point-like electron; rather, it is a complex system composed of quarks and gluons exhibiting many-body interactions. Electron scattering, where a high-energy electron scatters off a proton target, is a powerful probe in studying the internal structure of proton. If the electron and proton in this process are polarized they provide additional degrees of freedom to study the spin structure of the proton. The scattering cross-section of such processes can be parameterized by four structure functions, which can be obtained using different configurations of an unpolarized or polarized proton target. The fourth structure function, g2, describes the spin-dependent behavior of a proton when it is polarized transversely with respect to the electron polarization. While the other three structure functions have been measured over a wide range of kinematics, due to the experimental difficulty of measuring it, data for g2 remains scarce. The g2p Experiment, which ran in Experimental Hall A at Thomas Jefferson National Lab, will provide the first measurement of g2 for the proton at low momentum transfer (0.02 < Q2 < 0.2 GeV2) in the resonance region. These data will provide insight to several physics puzzles, such as why effective field theories fail to predict spin-dependent properties of the nucleon, specifically the proton polarizabilities. This talk will outline the theory and motivation behind the g2p experiment as well as present the current status of the analysis.
Bio:
Melissa Cummings is a native of Palmyra, NY. She graduated from the State University of NY at Geneseo in 2009 with a B.A. in Physics. She began her graduate studies at William & Mary in the fall of the same year, where she started working with Dr. Todd Averett. Her research has been focused on the g2p experiment at Jefferson Lab, which will provide the first measurement of the proton spin structure function g2 at low momentum transfer. After graduating, Melissa will begin working at the Institute for Defense Analyses in Alexandria, VA.