Well motivated theoretical models predict the annihilation of dark matter (DM) into standard model particles, a phenomenon which could be a significant source of photons in the gamma-ray sky. With its unprecedented sensitivity and its broad energy range (20 MeV to more than 300 GeV) the main instrument on board the Fermi satellite, the Large Area Telescope (LAT), might be able to detect an indirect signature of DM annihilations. In this work we revisit several interesting claims of extended dark matter emission made from analyses of Fermi-LAT data: First, based on three years of Fermi Large Area Telescope (LAT) gamma-ray data of the Virgo cluster, evidence for an extended emission associated with dark matter pair annihilation in the bb̄ channel has been reported by Han et al. (arxiv:1201.1003). After an in depth spatial and temporal analysis, we argue that the tentative evidence for a gamma-ray excess from the Virgo cluster is mainly due to the appearance of a population of previously unresolved gamma-ray point sources in the region of interest. These point sources are not part of the LAT second source catalogue (2FGL), but are found to be above the standard detection significance threshold when three or more years of LAT data is included. Second, we confirm the detection of a spatially extended excess of 2-5 GeV gamma rays from the Galactic Center (GC), consistent with the emission expected from annihilating dark matter or an unresolved population of about 10³ milisecond pulsars. However, there are significant uncertainties in the diffuse galactic background at the GC. We have performed a revaluation of these two models for the extended gamma ray source at the GC by accounting for the systematic uncertainties of the Galactic diffuse emission model. We also marginalize over point source and diffuse background parameters in the region of interest. We show that the excess emission is significantly more extended than a point source. We find that the DM (or pulsars population) signal is larger than the systematic errors and therefore proceed to determine the sectors of parameter space that provide an acceptable fit to the data. We found that a population of order a 10³ MSPs with parameters consistent with the average spectral shape of Fermi-LAT measured MSPs was able to fit the GC excess emission. For DM, we found that a pure τ⁺τ⁻ annihilation channel is not a good fit to the data. But a mixture of τ⁻τ⁻ and bb̄ with a (σν) of order the thermal relic value and a DM mass of around 20 to 60 GeV provides an adequate fit. We also consider the possibility that the GeV excess is due to nonthermal bremsstrahlung produced by a population of electrons interacting with neutral gas in molecular clouds. The millisecond pulsars and dark matter alternatives have spatial templates well fitted by the square of a generalized Navarro-Frenk-White (NFW) profile with inner slope γ = 1.2. We model the third option with a 20-cm continuum emission Galactic Ridge template. A template based on the HESS residuals is shown to give similar results. The gamma-ray excess is found to be best fit by a combination of the generalized NFW squared template and a Galactic Ridge template. We also find the spectra of each template is not significantly affected in the combined fit and is consistent with previous single template fits. That is, the generalized NFW squared spectrum can be fit by either of order 10³ unresolved MSPs or DM with mass around 30 GeV, a thermal cross section, and mainly annihilating to bb̄ quarks. While the Galactic Ridge continues to have a spectrum consistent with a population of nonthermal electrons whose spectrum also provides a good fit to synchrotron emission measurements. We also show that the current DM fit may be hard to test, even with 10 years of Fermi-LAT data, especially if there is a mixture of DM and MSPs contributing to the signal, in which case the implied DM cross section will be suppressed.

Using a measure of the jet energy resolution that relies on momentum balance in direct photon events, a correction to the modelled detector resolution is developed. The correction is produced by iteratively unfolding the model from the measured data. Jets in the model are then smeared using this correction, and the result is compared to the data using a χ2 test. This method is shown to be effective at improving the agreement between the data and the model, even when the model initially shows poor agreement to the data. / Graduate / 0798 / bmoir@ualberta.net

First, we review the basics of baryogenesis and models for baryogenesis in the early literature. Then, we discuss the main theme in this thesis, electroweak baryogenesis, which utilizes the electroweak phase transition. We present how the phase transition can be used to achieve baryogenesis. Next, we develop our model, which is the Standard Model with a singlet field coupled to the Higgs doublet negatively and to the right-handed neutrinos. It is a simple extension of the singlet Majoron model. We focus on numerical analysis of the model. Parameter space satisfying all the conditions are found and relevant quantities, such as the critical temperature, the Higgs mass, and the mixing angle are found as well. It turns out that LEP bound on the Higgs mass and the mixing angle is a strong constraint, and only a small fraction of parameter space is acceptable for attaining a strong enough phase transition for baryogenesis.

Thesis (Ph. D.)--University of Washington, 1999. / Vita. Includes bibliographical references (p. 100-102).

Thesis (Ph. D.)--University of Washington, 1999. / Vita. Includes bibliographical references (leaves 219-226).

Thesis (M.S.)--University of Texas at El Paso, 2009. / Title from title screen. Vita. CD-ROM. Includes bibliographical references. Also available online.

Thesis (Ph. D.)--University of Washington, 2007. / Vita. Includes bibliographical references (leaves 163-169).

The computational processes in the intermediate stages of the ventral pathway responsible for visual object recognition are not well understood. A recent physiological study by A. Pasupathy and C. Connor in intermediate area V4 using contour stimuli, proposes that a population of V4 neurons display bjectcentered,position-specific curvature tuning [18]. The “standard model” of object recognition, a recently developed model [23] to account for recognition properties of IT cells (extending classical suggestions by Hubel, Wiesel and others [9, 10, 19]), is used here to model the response of the V4 cells described in [18]. Our results show that a feedforward, network level mechanism can exhibit selectivity and invariance properties that correspond to the responses of the V4 cells described in [18]. These results suggest howobject-centered, position-specific curvature tuning of V4 cells may arise from combinations of complex V1 cell responses. Furthermore, the model makes predictions about the responses of the same V4 cells studied by Pasupathy and Connor to novel gray level patterns, such as gratings and natural images. Thesepredictions suggest specific experiments to further explore shape representation in V4.

Thesis (Honors)--College of William and Mary, 2009. / Includes bibliographical references (p. 54-55). Also available via the World Wide Web.

No description available.