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Joseph Matheson Karpie, Physics - Final Oral Exam for the Ph.D. Title: The Extraction of Parton Distributions from Lattice QCD
Abstract: A new method for calculating parton distribution functions from lattice QCD is implemented and studied. Lattice QCD calculable matrix elements with space-like separated fields have an analogous operator product expansion to experimental scattering cross sections and thus these matrix elements are known as “Good Lattice Cross Sections”. Using the colinear factorization approach, a Good Lattice Cross Section can be factorized to the short distance matching kernels that are computed in perturbation theory and the non-perturbative parton distribution functions. As a result, using the perturbative matching kernels and the non-perturbatively computed matrix elements, one can obtain the parton distribution functions. The nucleon and pion matrix elements are determined on a set of 2+1 flavors of clover improved quarks with heavier than physical pion mass. The determination of the parton distributions from Good Lattice Cross Sections constitutes an ill-posed inverse problem. Methods for accurate determination of parton distributions from the Good Lattice Cross Sections are studied. With the calculation of several Good Lattice Cross Sections, the determination of the parton distributions can be improved with a simultaneous analysis, similar to the global parton distribution fits to experimental cross sections.
Bio: At 12:57 pm on July 22,1992, Joe Karpie was born in Shawnee, OK. At 3 years old, he saw the land of his birth for possibly the last time as he left to be raised in the woods of Washington, GA. It was there that he learned his mother's knack with computers and his father's love of space; there are many more stars there than in places as populated as Williamsburg. At the age of 13, he moved to Fairport, NY where his growing interest in science and technology was fostered by groups such as the local FIRST robotics team. After graduating from Fairport High School in 2010, he enrolled at Rensselaer Polytechnic Institute, in Troy, NY, where he studied physics until 2014. In the fall of that year, he began his studies at William & Mary. In that first year, he began research with Prof. Orginos studying algorithms for Lattice QCD and the structure of protons. With any luck, his defense will be successful and in September he will begin working as a Postdoc for the Lattice QCD group at Columbia University, in New York City, NY.