Date of Award
Doctor of Philosophy (PhD)
Physics & Astronomy
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.
Kunkle, Joshua Milo, "A Search for Dark Matter Through Invisible Decays of the Higgs Boson With the Atlas Detector at the LHC" (2013). Publicly Accessible Penn Dissertations. 769.