ResBos2 : precision resummation for the LHC ERA
With the precision of data at the LHC, it is important to advance theoretical calculations to match it. Previously, the ResBos code was insufficient to adequately describe the data at the LHC. This requires an advancement in the ResBos code, and led to the development of the ResBos2 package. This thesis discusses some of the major improvements that were implemented into the code to advance it and prepare it for the precision of the LHC.The resummation for color singlet particles is improved from approximate NNLL+NLO accuracy to an accuracy of N$^3$LL+NNLO accuracy. The ResBos2 code is validated against the calculation of the total crosssection for DrellYan processes against fixed order calculations, to ensure that the calculations are performed correctly. This allows for a prediction of the transverse momentum and $\phi^*_{\eta}$ distributions for the $Z$ boson to be consistent with the data from ATLAS at a collider energy of $\sqrt{s}=8$ TeV. Also, the effects of choice of resummation scheme are investigated for the CollinsSoperSterman and CatanideFlorianGrazzini formalisms. It is shown that as long as the calculation of each of these is performed such that the order of the $B$ coefficient is exactly 1 order higher than that of the $C$ and $H$ coefficients, then the two formalisms are consistent. Additionally, using the improved theoretical prediction will help to reduce the theoretical uncertainty on the mass of the $W$ boson, by reducing the uncertainty in extrapolating the $\frac{d\sigma}{dp_T^W}$ distribution from the data for the $\frac{d\sigma}{dp_T^Z}$ distribution by taking the ratio of the theory predictions for the $Z$ and $W$ transverse momentum. In addition to improving the accuracy of the color singlet final state resummation calculations, the ResBos2 code introduces the resummation of noncolor singlet states in the final state. Here the details for the Higgs plus jet calculation are illustrated as an example of one such process. It is shown that it is possible to perform this resummation, but the resummation formalism needs to be modified in order to do so. The major modification that is made is the inclusion of the jet conesize dependence in the Sudakov form factor. This result resolves, analytically, the Sudakov shoulder singularity. The results of the ResBos2 prediction are compared to both the fixed order and parton shower calculations. The calculations are shown to be consistent for all of the distributions considered up to the theoretical uncertainty. As the LHC continues to increase their data, and their precision on these observables, the ability to have analytic resummation calculations for noncolor singlet final states will provide a strong check of perturbative QCD.Finally, the calculation of the terms needed to match to N$^3$LO are done in this work. Once the results become sufficiently publicly available for the perturbative calculation, the ResBos2 code can easily be extended to include these corrections, and be used as a means to predict the total crosssection at N$^3$LO as well.
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Electronic Theses & Dissertations
 Copyright Status
 Attribution 4.0 International
 Material Type

Theses
 Authors

Isaacson, Joshua Paul
 Thesis Advisors

Yuan, C.P
Schmidt, Carl
 Committee Members

Brock, Raymond
Piermarocchi, Carlo
O'Shea, Brian
 Date
 2017
 Subjects

Standard model (Nuclear physics)
Quantum chromodynamics
Particles (Nuclear physics)
Large Hadron Collider (France and Switzerland)
 Program of Study

Physics  Doctor of Philosophy
 Degree Level

Doctoral
 Language

English
 Pages
 xvi, 240 pages
 ISBN

9780355514698
0355514699
 Permalink
 https://doi.org/doi:10.25335/vt7akp55