Improved neutrino point source search method for IceCube's high energy starting event sample
Date
2017
Authors
Aartsen, Mark Gerald
Editors
Advisors
Hill, Gary C.
Whelan, Ben
Protheroe, Raymond John
Whelan, Ben
Protheroe, Raymond John
Journal Title
Journal ISSN
Volume Title
Type:
Theses
Citation
Statement of Responsibility
Conference Name
Abstract
High Energy Neutrino Astronomy is a new field that has the potential to solve the
mystery of the origin of cosmic ray particles, the highest energy particles that have
been observed. The IceCube Neutrino Observatory has recently discovered the existence
of a high energy astrophysical neutrino
flux. We are able to calculate for our
"track-like" sub-population of events a directional origin to within a square degree,
yet it remains difficult to establish whether these neutrinos come from bright distinguishable
sources or a sea of individual weak neutrino producers. The current goal
of neutrino point source analyses is the observation of a bright neutrino source above
expected background rates of neutrinos, in our case both from a uniform distribution
of astrophysical neutrino sources and background neutrino events produced in
cosmic ray interactions with our own atmosphere. This thesis presents a new form
of point source analysis that tests the data under the model of the combination
of multiple background hypotheses and a single point source hypothesis, where the
predicted background distributions can be produced through simulation. We apply
this analysis to the High Energy Starting Event sample produced by IceCube, and
show how this analysis differs to previous analyses on these events. We find that
the fit using a background in the likelihood that does not match the distribution
of the events can result in a bias in the fitted strength of a point source, and that
the relative power of the analysis compared to the previous point source analysis
can depend on the point source location, where the power is seen to be comparable
in the southern sky but improved in the northern sky. Our results from applying
our new form of point source analysis to the data do not show strong evidence for
a point source hypothesis, with p-values of 0.468 for all events in our sample and
0.922 for a subset of shower topology events in our sample.
School/Discipline
School of Physical Sciences
Dissertation Note
Thesis (Ph.D.) -- University of Adelaide, School of Physical Sciences, 2018
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