Undergraduate Research at Jefferson Lab

Impact Study of EIC's Parity Violating Deep Inelastic Scattering Data

Student: Justin Hink

School: University of Arizona

Mentored By: Nobuo Sato and Wally Melnitchouk

The momentum distributions of partons inside the nucleon are not fully understood, and new parity- violating deep-inelastic scattering (PVDIS) data will help ascertain some of the less well-determined flavor contributions, such as from strange quarks. Furthermore, PVDIS data are sensitive to the fundamental electroweak parameter sin²θ_W, with θ_W the Weinberg angle, which determines the weak couplings of fermions in the framework of the Standard Model. The focus of this project is to perform an impact study of future Electron-Ion Collider data on both our knowledge of parton distribution functions (PDFs) and sin²θ_W, and set limits on beyond the Standard Model physics with different chiral structure. First, general parameters for the PDFs andsin²θ_W were input into the JAM global QCD analysis machinery to fit world data on inclusive DIS. Next, the strength of sin²θ_W at the mass of the Z boson was openly parametrized, while sin²θ_W at other energy values were calculated using the traditional renormalization group equations (RGEs). The fit PDF curves were found with a χ² less than the set limit of 2. The interpolated sin²θ_W values calculated through the RGEs revealed two bands of solutions: one where the current Standard Model resides, and the other where physics beyond the standard model may be found. The sin²θ_W values interpolated without relying on the RGEs displayed a broad limit that matched the two bands of solutions. The fit curves will help limit the theoretical ranges of parameters to a smaller domain, and hence improve our knowledge of the PDFs and of sin²θ_W. To get a better understanding of the two bands of solutions, sin²θ_W data from previous SLAC and Jlab PVDIS experiments will be implemented into the parameters. As the parameter ranges diminish, the value of sin²θ_W will be better determined and the true shapes of the PDFs more clearly revealed, which will enhance the collective knowledge of the structures of hadrons.

[Watch the presentation on YouTube]