Date of Award

Spring 1-1-2017

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

First Advisor

Kevin Stenson

Second Advisor

William T. Ford

Third Advisor

Alysia Marino

Fourth Advisor

Oliver DeWolfe

Fifth Advisor

Michael Shull

Abstract

We present a search for supersymmetry in purely hadronic final states with large missing transverse momentum using data collected by the CMS detector at the CERN LHC. The data were produced in proton-proton collisions with center-of-mass energy of √s = 13 TeV and correspond to an integrated luminosity of 35.9 fb-1. Data are analyzed with variables defined in terms of jet multiplicity, bottom quark tagged jet multiplicity, the scalar sum of jet transverse momentum, the magnitude of the vector sum of jet transverse momentum, and angular separation between jets and the vector sum of transverse momentum. We perform the search on the data using two analysis techniques: a boosted decision tree trained on simulated data using the above variables as features and a four-dimensional fit with rectangular search regions. In both analyses, standard model background estimations are derived from data-driven techniques and the signal data are separated into exclusive search regions. The observed yields in the search regions agree with background expectations. We derive upper limits on the production cross sections of pairs of gluinos and pairs of top squarks at 95% confidence using simplified models with the lightest upersymmetric particle assumed to be a weakly interacting neutralino. Gluinos as heavy as 1960 GeV and top squarks as heavy as 980 GeV are excluded. The limits significantly extend the exclusions obtained from previous results.

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