Towards Precision Standard Model Calculations

Abstract

For many years the consistency of the Standard Model(SM) of particle physics has been unflinching. The structure and content of the Standard Model has remained whole in the face of shockingly many experimental tests. Predicting the existence of new particles and yielding incredibly accurate calculations of fundamental measurements have been the hallmark of the Standard Model. Currently, experimentalists are testing several Standard Model quantities to such precision that 5th order terms are needed in theoretical calculations to match this precision. Never-the-less, the predictions of the Standard Model have kept pace with experiment and have yet to be contradicted. Unfortunately, this incredible stretch of experimental validation comes at a cost. Several very large problems still are without solutions and finding them in the particle content of the Standard Model alone is unlikely. The huge range of scales seen in nature, a dark matter candidate, and the cosmic baryon asymmetry still loom as major flaws in the Standard Model. In this manuscript we aim to increase the accuracy of several Standard Model predictions to push the experimental limits of the Standard Model. We start with a brief introduction to the Standard Model and its sector we will be mainly concerned with, namely QCD. In Chapter 2, we will consider the Standard Model as an effective field theory for a new physics model that resides at a mass scale much higher than the electro-weak scale. By interpreting the SM as an effective theory it allows us to extend the Standard Model Lagrangian with new, higher-dimensional operators that depend on the scale of new physics. We then calculate the next-to-leading order corrections to these operators in QCD and combine these calculations with parton showers via the \\texttt{POWHEG} method. In the final section of Chapter 2 we present a discussion of the bounds on the scale of new physics that can be drawn from comparing our results to Large-Hadron-Collider(LHC) searches. In the third chapter of this manuscript, we will briefly introduce the importance of W+charm events at the LHC followed by a discussion of NLO QCD calculations and heavy meson fragmentation resummation. Next, we give a general method for combining a fixed order, massive calculation with a massless calculation with large logarithms resummed. Numerical results of resummation and an implementation of the afore mention method are discussed followed by future outlook.

Cite this paper

@article{girard2018towards,
  title = {{Towards Precision Standard Model Calculations}},
  author = {Girard, Michael},
  journal = {eScholarship (California Digital Library)},
  year = {2018}
}

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