Date of Award

2013

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Graduate Group

Physics & Astronomy

First Advisor

Elliot Lipeles

Abstract

Diboson physics provides insight into a wide variety of processes

that are produced copiously at the LHC. Of particular interest

are events where leptons and neutrinos are produced, strong signatures

of electroweak physics. The study of electroweak physics is

essential to understanding the Standard Model and in searches

for phenomena outside the Standard Model.

The most sensitive channels that contributed to the discovery

of the Higgs boson searched for decays to dibosons.

This thesis will present four analyses that utilize

charged leptons and neutrinos whose presence are

inferred from the missing transverse momentum.

Two measurements of Standard

Model cross sections will be presented. The WW cross section is measured

using 35 pb-1 of data collected in 2010 and is

one of the earliest measurements of diboson processes

at the LHC. The ZZ cross section is measured using

4.6 fb-1 of data collected in 2011. A search

for the Higgs in the WW decay channel is presented

also using 4.6 fb-1 of data collected in 2011.

This analysis did not have the sensitivity to discover the

Higgs boson, but when data were added in 2012 this channel

contributed significantly to its discovery.

Finally a search for anomalous invisible decays of the Higgs boson

using 4.6 fb-1 of

data taken in 2011 and 13.1 fb-1 of data taken in 2012

will be presented.

This search is sensitive to new physics that couples to the Higgs

boson that would result in an increased rate of decays to invisible particles.

One possible scenario is that dark matter couples to the Higgs boson.

If the mass of the dark matter particle is less than half of the

mass of the Higgs boson decays to dark matter increase

its invisible branching fraction.

Dark matter is a significant contribution

to the makeup of the universe, but very little is known about it.

This search provides additional limits on how dark matter can couple

to the Standard Model.

No excess of events is observed in this search and

limits are placed on the allowed invisible branching fraction.

These limits are interpreted in the context of simple Higgs portal

models to place constraints on the allowed dark matter mass and

interaction cross section. The results are compared with

current limits on dark matter and place significant restrictions

on the allowed dark matter mass and cross section within these models.

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