Chien-Peng ("C.-P.") Yuan

Current understanding of high energy physics is embodied in the Standard Model (SM). Protons and neutrons, and all other strongly interacting particles, are composed of fundamental particles called partons (quarks and gluons). Interactions between the partons are described by the theory of Quantum Chromodynamics (QCD). My research involves the interplay between QCD theory and experimental data from many experiments, including recent experiments at the CERN Large Hadron Collider (LHC). This global analysis of data is necessary to deepen the understanding of QCD, and to determine the probability distributions of the partons in the proton. The resulting CTEQ (CTEQ-TEA) Parton Distribution Functions have been essential to the interpretation of experiments at the world's leading high energy collider facilities: Fermilab (Batavia, IL), RHIC (Brookhaven, NY), DESY (Hamburg, Germany), and CERN (Geneva, Switzerland). With that, we continue our world-leading contributions to enable making precision predictions on collider phenomenology and precise determination of the SM parameters at lepton-hadron and hadron-hadron colliders, relevant to the High Energy Physics and Nuclear Physics communities. The most recent sets of CTEQ-TEA (CT18) PDFs can be found at http://hep.pa.msu.edu/cteq/public/ct18.html.

Transverse momentum (or QT) resummation generalizes the conventional collinear factorization in QCD theory for hadronic processes to calculate both normalization and shape of particle distributions. Since its conception in the late 1970's, QT resummation has been successfully applied to study all-order structure of hadronic differential distributions and provide excellent predictions for a variety of experiments. Its main features and differences from Monte-Carlo showering methods are discussed in a brief overview of resummation theory at http://hep.pa.msu.edu/resum/theory_overview.html. Our group is actively involved in the development of transverse momentum resummation methods in essential collider processes, relevant to the phenomenology of weak gauge (W and Z) bosons, Higgs boson, photon pairs, and New Physics particles (such as W-prime and Z-prime bosons). They have been implemented in the ResBos code. Details can be found at http://hep.pa.msu.edu/resum.

At high energy colliders, top quark can be singly produced via electroweak interaction. In contrast to the top quark pair production via QCD interaction, the special feature of this process is that its production rate is proportional to the coupling of t-b-W. Hence, a precise determination of its production rate can test the coupling of top to the W gauge boson. Since New Physics effects can modify this particular coupling, it is important to have a very precise theory calculation by including higher order corrections predicted by the SM. I proposed how to detect the single top events at hadron colliders back in the early 1990's and performed higher order calculation to improve the theory prediction on its production and decays, and to explore the potential of using top quark polarization to test SM and distinguish New Physics models. A news article entitled ``MSU scientists find evidence for rare single top quarks'' can be found at https://pa.msu.edu/news-events/news/single-top-quarks/

Some publically-available programs for calculating the cross sections and distributions of various scattering processes in high energy collider physics can be found at https://pa.msu.edu/research/high-energy-physics/hep-theory/.