Global QCD Analysis and Precision Electroweak Physics in High Energy Collier Phenomenology

This award funds the research activities of Professor C.-P. Yuan at Michigan State University. Elementary particle physics addresses the question "What is matter made of?" on the most fundamental level --– which is to say, on the smallest length scales. Our current understanding is that protons and neutrons, and all other strongly interacting particles, are composed of fundamental particles called partons (quarks and gluons). The strong interactions between the partons are described by the theory of Quantum Chromodynamics (QCD). As part of this research project, Professor Yuan aims to develop theoretical methods to extract information from the QCD theory which are critical for interpreting experimental data around the world, including recent experiments at the CERN Large Hadron Collider (LHC). As a result, research in this area advances the national interest by promoting the progress of science in one of its most fundamental directions: the discovery and understanding of new physical law. This project is also envisioned to have significant broader impacts. Professor Yuan will involve postdocs in his research, and thereby provide critical training for junior physicists beginning research in this field. He also intends to give public lectures on their research results and develop new course curricula based on the results of their research. More technically, Professor Yuan will extract the most updated CTEQ-TEA Parton Distribution Functions (PDFs) from a global analysis of the experimental data. (CTEQ is an acronym for "Coordinated Theoretical Experimental Project of QCD", and TEA for "Tung et al".) He will expand the theoretical capabilities of the analysis to include corrections from higher-order QCD interactions, heavy quark mass effects, next-to-leading order quantum electrodynamics (QED) interactions, and transverse momentum resummation. He will also refine the techniques for analyzing the PDF uncertainties and the correlations among the predictions of various physical observables, and investigate the implications of PDFs and their associated uncertainties on the most important physical processes at colliders, particularly at the LHC. Measurements of W, Z, top quark pair, single top quark and Higgs boson productions at the LHC, including both inclusive rates and various kinematical distributions, will provide major new input to the determination of PDFs during the next few years. At the same time, refinements of the PDFs are crucial both for testing the Standard Model at greater precision and for probing New Physics effects at high energy colliders. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.