T2K is a long-baseline accelerator neutrino oscillation experiment using the high-intensity ν_μ beam produced at J-PARC. Sitting 295 km away, the giant Super-Kamiokande detector, a 50 kt water tank instrumented with 11,129 photosensitive detectors, sees a narrow band beam peaked at 600 MeV. The baseline to energy ratio is finely tuned for studying neutrino oscillations at the atmospheric neutrino squared-mass splitting. The beam is also sampled 280m downstream of the neutrino production target by a series of finely segmented solid scintillator and time projection chamber detectors. Observing changes in the neutrino beam between the two detectors allows oscillation parameters to be accurately extracted. A ν_μ-disappearance analysis was performed on the combined T2K Run 1+2+3+4 dataset, corresponding to integrated J-PARC neutrino beam exposure of 6.57x10²⁰ POT, in a framework of three active neutrino flavour oscillations including matter effects in constant-density matter. The observed reconstructed energy spectrum of 1 μ-like ring events was fitted, and separate fits were made for the normal and the inverted mass hierarchies.

Doctor of Philosophy / Department of Physics / Glenn Horton-Smith / In March 2012, the Double Chooz reactor neutrino experiment published its most precise result so far: sin[superscript]2 2theta13 = 0.109 +/- 0.030(stat.) +/- 0.025(syst.). The statistical significance is 99.8% away from the no-oscillation hypothesis. The systematic uncertainties from background and detection efficiency are smaller than the first publication of the Double Chooz experiment. The neutron detection efficiency, one of the biggest contributions in detection systematic uncertainties, is a primary topic of this dissertation. The neutron detection efficiency is the product of three factors: the Gd-capture fraction, the efficiency of time difference between prompt and delayed signals, and the efficiency of energy containment. [superscript]252 Cf is used to determine the three factors in this study. The neutron detection efficiency from the [superscript]252 Cf result is confirmed by the electron antineutrino data and Monte Carlo simulations. The systematic uncertainty from the neutron detection efficiency is 0.91% used in the sin[superscript]2 2theta13 analysis. The seasonal variation in detector performance and the seasonal variations of the muon intensity are described in detail as well. The detector stability is confirmed by observation of two phenomena: 1) the [electron antineutrino] rate, which is seen to be uncorrelated with the liquid scintillator temperature, and 2) the daily muon rate, which has the expected correspondence with the effective atmospheric temperature. The correlation between the muon rate and effective atmospheric temperature is further analyzed in this thesis to determine the ratio of kaon to pion in the local atmosphere. An upper limit on instability of the neutron detection efficiency is established in the final chapter. The systematic error, 0.13%, from the relative instability is the deviation of the calibration runs. This thesis concludes with the potential systematic errors of neutron detection efficiency and estimation of how these potential systematic errors affect the result of sin[superscript]2 2theta13.

In order to be able to determine neutrino mass hierarchy in the neutrino oscillation experiment JUNO we need to understand the dependence of the response of the signal from the scintillator on the deposited energy inside the scintillator. We measure the nonlinearity of the signal response via the Compton scattering inside the scintillator and via the precision gamma spectroscopy inside the HPGe detector. We observe effects of different parameters on the experiment via the Monte Carlo simulations. We also improve the data processing of the measured data and discuss what improvements of the experiment we can use in the future.

Thesis advisor: Andrzej Herczynski / The magnetic pendulum investigated in this experiment closely models various forms of the gravitational pendulum. However, the apparatus used in this experiment allows for greater insight as the constant and periodic forces can be easily varied. This project extends the previous work of Sang-Yoon Kim and Francis Moon on the magnetic pendulum by including an additional degree of freedom. This additional degree of freedom allows for a greater understanding of the bifurcation points observed. / Thesis (BS) — Boston College, 2007. / Submitted to: Boston College. College of Arts and Sciences. / Discipline: Physics. / Discipline: College Honors Program.

Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1982. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING / Bibliography: leaf 47. / by Michelle Renée Hunt. / B.S.

The Mediterranean region has experienced persistent drying since the middle of the 20th Century and global climate models project further drying in the future as a consequence of increasing greenhouse gases. The Mediterranean region is also known to oscillate between decades of relatively wet and dry conditions due to the strong influence of multidecadal North Atlantic Oscillation (NAO). It is therefore of great importance to understand the relationship between forced long-term drying resulting from human influences and those due to natural variability. To this end, we used observations, reanalyses and comprehensive global climate models in this thesis research. The roles of anthropogenic climate change and internal climate variability in causing the Mediterranean region's late 20th Century extended winter drying trend were examined using 20th Century observations as well as 19 coupled climate models from the CMIP3. The drying was strongly influenced by the robust positive trend in the NAO from the 1960s to the 1990s. Model simulations and observations were used to assess the probable relative roles of radiative forcing and internal variability in explaining the circulation trend that drove much of the precipitation change. It was concluded that the radiatively forced trends were a small fraction of the total observed trends. Instead it was argued that the robust trends in the observed NAO and Mediterranean rainfall during this period were largely due to multidecadal internal variability with a small contribution from the external forcing. Differences between the observed and NAO associated precipitation trends are consistent with those expected as a response to radiative forcing. The radiatively forced trends in circulation and precipitation are expected to strengthen in the current century and these results highlight the importance of their contribution to future precipitation changes in the region. The Mediterranean precipitation climatology and trend were further examined by comparing the newest generation of global climate models (CMIP5) used in the Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report, to the previous generation (CMIP3) and to observations over the latter half of the 20th Century for both the summer and winter half years. The observed drying trend since 1950 was predominantly due to winter drying, with very little contribution from the summer. However, in the CMIP5 multimodel mean, the precipitation trend since 1950 is evenly divided throughout the seasonal cycle. This may indicate that in observation, multidecadal internal variability, particularly that associated with the NAO, dominates the wintertime trend. An estimate of the observed externally forced trend showed that winter drying dominated in observations but the spatial patterns were grossly similar to the multimodel mean trend. The similarity was particularly robust in the eastern Mediterranean region, indicating a radiatively forced component being stronger there. These results also revealed modest improvement for the CMIP5 multimodel ensemble in representation of the observed six-month winter and summer climatology. We further explored the detailed mechanisms leading to the NAO-associated precipitation change, such as the role of the change in mean circulation versus that of the storm tracks in the regional moisture budget, which had not been investigated previously. We employed a moisture budget analysis using 15 CMIP5 models and the ERA-Interim Reanalysis to investigate the relationship between the NAO and the various moisture budget terms for the six-month winter and summer. Compared with the ERA-Interim, the models performed well in their simulation of the relationship between the naturally varying NAO and the large-scale moisture budget. Our results indicated that the shift in the midlatitude transient eddies induced modest moisture convergence, rather than divergence, over the Mediterranean under a positive NAO. The reduction in precipitation in this region during a positive NAO was dominated by the mean moisture divergence, which opposed the transient contribution. There were significant differences between the patterns of NAO-induced moisture budget anomaly and changes due to external radiative forcing. Under radiative forcing there was enhanced evaporation over the Mediterranean Sea, Italy and eastern Europe and drying by the shift in the wintertime storms over nearly all of Europe and the Mediterranean. Under a positive phase of the NAO, on the other hand, there was modest reduction in evaporation and wetting by the storms over the Mediterranean, and drying over northern Europe. The dependence of the Mediterranean moisture budget on the NAO was similarly explored in the summer half of the year and in this season the models exhibited more disagreement with observations, but otherwise showed the similar results as winter. The stronger anthropogenic induced drying signal over the eastern Mediterranean provided a basis to examine the possible cause and impact of the recent severe and persistent drought in Syria that occurred directly prior to the uprising of 2011. The drought devastated Syrian agriculture, resulting in food shortages, widespread unemployment, the collapse of rural social structure and a mass migration of agricultural refugees to Syria's urban areas. Anger at the government's failure to ameliorate conditions was one spark for the uprising that evolved into civil war. We found that though droughts occur periodically in Syria due to natural causes it is likely that the recent drought was more extreme due to the century long drying trend caused by increased radiative forcing. It was estimated that the anthropogenic trend made a drought of such severity several times more likely. Droughts as persistent as the recent one are projected to be commonplace in a future warmer world.

The IceCube Neutrino Observatory at the South Pole is the world's largest neutrino detector with over 1km^3 of instrumented Antarctic ice. While it has been primarily designed to observe astrophysical neutrinos, this size also allows it to collect vast quantities of atmospheric neutrinos. These high-statistics datasets allow for measurements of the properties of neutrinos, in particular the phenomena of neutrino oscillation. One of the outstanding questions in this field is that of the neutrino mass ordering (NMO). The Precision IceCube Next Generation Upgrade (PINGU) is a proposed low-energy extension to IceCube for which a determination of the NMO is a priority science goal. The current low-energy atmospheric neutrino experiment at the South Pole, DeepCore, has been successfully collecting data since 2011. In this thesis the potential of this existing data to determine the NMO has been explored. While it was not expected to have a large sensitivity, this work has explored a Feldman-Cousins treatment for converting the delta-chi^2 between the two discrete mass ordering hypotheses into the standard Gaussian significance metric. Using 2.7 years of data from the DeepCore detector, the inverted mass ordering was preferred at the level of 0.05sigma. The second aspect of this thesis was to study the impact of the systematic uncertainties on the NMO determination. This particular analysis was actually statistics-limited and so the only impactful systematic uncertainties were the parameters that govern atmospheric neutrino oscillations, theta_23 and Deltam^2_31. Therefore, to improve the NMO results, these parameters were constrained by including the global information on them in the fits, yielding a new NMO sensitivity of 0.29sigma. This new global fit also yields measurements of the oscillation parameters of Deltam^2_32,NO=(2.443+/-0.037)e-3eV^2 and sin^2theta_23,NO=0.442+0.026-0.018 for the hypothesis of the normal mass ordering and Deltam^2_32,IO=(-2.510+/-0.036)e-3eV^2 and sin^2theta_23,IO=0.579+0.019-0.021 for the hypothesis of the inverted mass ordering. In addition to the work on the neutrino mass ordering, this thesis also investigated two issues related to predictions of the flux of atmospheric particles. The first related to the treatment of the predictions of the atmospheric neutrino flux, provided in binned tables. Crucially, these contain values representative of the integral of the flux across that bin and so an integral-preserving interpolation must be used. One such method will be presented along with a discussion of how it performs in the two-dimensional case of the atmospheric neutrino flux. The second issue related to quantifying uncertainties on the background muon distributions observed with the IceCube detector coming from the uncertainties on the initial cosmic ray flux. This involved performing a global fit on the available cosmic ray flux measurements and then propagating these uncertainties in to the muon distributions. To finalise this section, the exact manner in which these uncertainties can be included in the physics analyses of IceCube will be discussed.

The continental shelf on the western side of the Antarctic Peninsula is a region of substantial climate and ecosystem change. The Long Term Ecological Research project at Palmer Station has been sampling and studying the shelf ecosystem and physical environment since 1990. This dissertation seeks to improve our understanding of the subtidal and intraseasonal (hereafter defined together as 3-100 days) circulation on the neighboring continental shelf and is particularly motivated by the aims of the project to understand (1) how lateral transports of scalar parameters such as heat affect the vertical stratification and (2) how coastal canyon heads are linked to the larger-scale shelf circulation and why they are such ecologically productive environments. In this dissertation we study: (1) the origin and mixing of mesoscale eddies as agents of heat transport and stirring; (2) the spatial coherence of shelf-scale barotropic velocity fluctuations, their origin through flow-topography interaction with Marguerite Trough Canyon, and their associated heat transports; and (3) the wind-driven dynamics of the long-shore flow manifested through coastal trapped waves and their ability to both induce upwelling at a coastal canyon head and to modulate isopycnal depth at the continental shelf-break. This work takes an observational approach, utilizing the rare and expansive data set afforded by the long-term sampling program including shipboard CTD and ADCP profiles, moored current meter time series, and CTD profiles from an autonomous underwater vehicle.

No description available.

The Madden-Julian Oscillation is a tropical atmospheric phenomenon detected as anomalies in zonal winds, convection and cloudiness. This perturbation has a definitive timescale of about thirty to sixty days, allowing its signal to be extracted from background data. The Madden-Julian Oscillation originates over the western Indian Ocean and generates a convective region which moves east along the equatorial region. This perturbation is thought to contribute to the timing and intensity of the eastern hemisphere monsoons, the El Niño/ Southern Oscillation and tropical storms and cyclones. The current understanding of the Madden-Julian Oscillation is that it restricts the bulk of its' influence to the tropics, however some evidence suggested that the impact is more extensive. Analysis of about 30 years of data showed significant modulation of rainfall by the equatorial passage of the MJO. The real-time multivariate Madden-Julian Oscillation Index was used to estimate the location and amplitude of the Madden-Julian Oscillation, and forms the basis of the basic rainfall prediction tool developed. The method developed here clearly linked the low latitude passage of the Madden-Julian Oscillation with suppressed and enhanced rainfall events in the Australasian region and beyond. A rudimentary forecasting capability at the intraseasonal time scale has been developed suitable for assisting Australian agricultural sector. A subsequent and independent analysis of global mean sea level pressure anomalies provided evidence of teleconnections between the Madden-Julian Oscillation and higher latitude atmospheric entities. These anomalies confirm the existence of teleconnections capable of producing the rainfall pattern outputs. The MJO is strongly influenced by the season. However the seasonally dependant analysis of rainfall with respect to the Madden Julian Oscillation conducted was inconclusive, suggesting aspects of the MJO influence still require clarification. Considering the importance of rainfall variability to the Australian agricultural sector the forecasting tool developed, although basic, is significant.