Grant: Subatomic Physics Envelope - Individual

The research in this proposal aims to elucidate the dynamics of the Standard Model (SM) of particle physics, both for SM-dominated processes, and in determining SM contributions to processes currently being studied in intensive, ongoing experimental searches for beyond-the-Standard-Model (BSM) physics at major experimental facilities throughout the world. A precision understanding of SM contributions is crucial to identifying the presence of any BSM effects. It is particularly important to quantify the effects of strong interaction, whose strength makes them both numerically significant and amenable to use of a more restricted set of theoretical techniques. These effects will be evaluated using Quantum Chromodynamics (QCD), the theory of the strong (nuclear and sub-nuclear) interactions, with much of the work involving large scale numerical computations (lattice QCD). Some of the highlights of the proposed research are as follows: (1) Precision determinations of the strong coupling (the constant determining the strength of the strong interactions in the SM): Improvements to the currently available precision are required to allow BSM effects to be searched for using precision measurements of Higgs boson couplings, one of the major goals of the experimental program at the proposed future International Linear Collider. This proposal involves three different independent approaches to such an improved determination. (2) Work on the SM strong interaction contributions to the anomalous magnetic moment of the muon: The current difference between the experimental determination and the SM prediction for this quantity represents one of the longest-standing, and most intriguing, pieces of evidence for the presence of BSM physics. This has prompted more than a decade's worth of intense, ongoing interest across the particle physics community. A new experiment at Fermilab in the US, aimed at reducing the experimental error by a factor of 4, will begin running in 2017. Improving the accuracy of the SM prediction is critical to taking advantage of this improved precision. The current proposal involves several individual projects which will contribute to this improved precision. (3) Work on identifying channels supporting exotic hadronic states: Since the advent of the quark model in the 1960s, there has been intense interest in understanding whether or not strongly interacting particles other than the ""ordinary"" quark model quark-antiquark mesons and three-quark baryons exist in nature. Our group recently provided compelling theoretical evidence for the existence of one such state, and will perform targeted theoretical searches for other candidates. Extensive experimental programs searching for such states exist or are anticipated at current and near-future large-scale experimental facilities. There is thus strong interest in such results/predictions from the experimental community.