CAREER: Constraining Parton Distribution Functions for New-Physics Searches

Michigan State University, East Lansing MI

Investigators

Abstract

This project concerns physics at the femtoscale (a million times smaller than the nanoscale) within nucleons, the fundamental building blocks of the atomic nuclei. As ever improving precision in experiments puts theories to more stringent tests, highly accurate theoretical calculations are required to advance our understanding of the nucleon structure. In this context, this project will contribute precise numerical calculations of nucleon properties in support of the experimental programs at state-of-the-art experimental facilities, such as the Brookhaven and Jefferson Laboratories in the United States, GSI in Germany, and J-PARC in Japan. This research involves the development of high-performance computational methods and large-scale numerical calculations on supercomputers. This project provides excellent training opportunities for students on both theoretical and numerical methods. This project aims to improve the systematic uncertainties in lattice-QCD (LQCD) determinations of the parton distribution functions (PDFs), to leverage these results to reduce uncertainties in global PDF fits, and to use them to provide more precise Standard-Model inputs to aid new-physics searches and guide upcoming QCD-frontier research. In high-energy physics, PDF uncertainty is the dominant error in the theoretical input to quantities such as the Higgs-production cross section. In nuclear physics, investment at RHIC and JLab 12-GeV has been made to explore the sea-quark and gluon structure of nucleons. The PI made the first LQCD calculation of the Bjorken-x dependence of the PDFs using the "large-momentum effective theory" method. The latter is expected to open new doors of opportunity to the study of multidimensional proton structure, such as generalized parton distributions (GPDs) and transverse-momentum distributions (TMDs). By the end of the award period, the PI will work with the global PDF analysis community to incorporate LQCD results, producing fits with the improved precision needed for new-physics searches at LHC and to make predictions for upcoming measurements at current nuclear laboratories and the future EIC.