Baylor University
Department of Physics
College of Arts and Sciences

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Elementary Particle Theory - The Standard Model

The goal of theoretical elementary particle physics is to understand the most fundamental laws which govern our universe, and to understand the structure and nature of the universe at the deepest level. Theorists at Baylor are approaching these questions from a variety of perspectives.

Standard Model Phenomenology

The interactions of all known subatomic particles can be described by a single theoretical framework known as the "Standard Model". This model describes matter in terms of leptons (including electrons, neutrinos, ...) and quarks, together with their interactions via force-carriers called "gauge bosons", which include the photon, W and Z bosons, and gluons. The theory is modeled by a gauge group SU(2)L x U(1) x SU(3)c which encompasses all known forces except gravity, which is too weak on small scales to have been observed in any particle physics experiments. An important constituent of the standard model is the Higgs boson, which is associated with a Higgs field which causes most of the particles in the standard model to acquire a mass.

Large high-energy physics laboratories such as the ones at FermiLab, SLAC, and CERN, have been very successful in verifying the predictions of the standard model, with the exception of finding the Higgs boson. Discovering and uncovering the properties of the Higgs boson is the primary goal of particle colliders currently under construction, including the Large Hadron Collider (LHC) at CERN. Interpreting the results of high-energy collisions in terms of the standard model requires high precision calculations of the various processes and backgrounds which are to be observed. The theoretical high energy physics phenomenology group at Baylor focuses on rigorous quantum field theoretic investigations an emphasis on the theory of higher order radiative corrections to the SU(2)L x U(1) x SU(3)c model of elementary particle interactions. Dr. Ward is engaged in constructing computer realizations of the quantum field theory calculations required for high-precision tests of the Standard Model.

Collision properties are calculated in the context of realistic detector simulations using "Monte Carlo" event generators, which randomly generate scattering events based on the predictions of quantum field theory. The Monte Carlo realization of the radiative corrections has played an essential role in precision Standard Model tests and new physics probes in the LEPII final data analysis, and in the preparation of the physics for the CERN LHC. These calculations also have immediate consequences for the ongoing studies at the lower-energy FNAL Tevatron and for precision Standard Model tests at the B-Factories and at the Φ-Factory. High precision is achieved via resummation methods based on the theory of Yennie, Frautschi and Suura.

Feynman graphs for radiative corrections to pair production

The methods developed by Yennie, Frautschi and Suura for resumming the infrared terms in quantum field theory can also be applied to perturbative quantum gravity. Dr. Ward has been investigating this, and in the process has found a new way to analyze classes of quantum gravity graphs which may otherwise have been expected to produce divergences. This may provide a fruitful new approach to the long-standing problem of quantizing gravity.

If you are interested in studying the role of higher-order radiative corrections in particle physics phenomenology, you may contact Dr. Ward.