Dr. April Townsend successfully defends PhD Thesis

Dr. April Townsend successfully defended her PhD Thesis about "Transverse Single-Spin Asymmetries in pion-induced Drell-Yan and J/Psi Production at COMPASS" on June 28, 2022. April analyzed data taken with the COMPASS experiment at CERN in the years 2015 and 2018, when the SPS 160 GeV pion beam was impinging on the COMPASS transversely polarized proton target. April studied azimuthal modulations in the production of muon pairs emerging in the pion-proton Drell-Yan process. There is a specific set of transverse-momentum-dependent (TMD) spin asymmetries when the proton is transversely polarized, which when measured to be non-zero are indicative of spin-orbit or spin-spin couplings in the proton. In particular, there is the Sivers effect, which is closely linked to the presence of orbital angular momentum of quarks and gluons in the proton. April extracted all TMD-related asymmetries from the complete COMPASS data set, which is the only existing one worldwide in standard Drell-Yan and J/Psi production. The latter process is expected to carry sensitivity to gluon TMDs, while the COMPASS Drell-Yan asymmetries are sensitive to quark TMDs. Not only did April analyze the COMPASS data, but she also served as production manager for the 2015 and 2018 data using the petascale capabilities of TACC's NSF-funded supercomputer Frontera, for which our UIUC COMPASS group had secured a computing allocation. In the data production, the raw data as coming in digitized form from the detectors is turned into physical quantities like momenta and energy of the emerging particles, which requirescomplex reconstruction algorithms and input databases to be set up in a precise way. April was also a member of the team that took care of repairing our group's drift chamber DC5 at CERN. April started as an Instructor of Physics and Mathematics at Fairmont State University in September 2022 and continues to work on the finalization of her COMPASS data analysis and publication in her free time.