Geoneutrinos and reactor antineutrinos at SNO+

In the heart of the Creighton Mine near Sudbury (Canada), the SNO+ detector is foreseen to observe almost in equal proportion electron antineutrinos produced by U and Th in the Earth and by nuclear reactors. SNO+ will be the first long baseline experiment to measure a reactor signal dominated by CANDU cores ($\sim$55\% of the total reactor signal), which generally burn natural uranium. Approximately 18\% of the total geoneutrino signal is generated by the U and Th present in the rocks of the Huronian Supergroup-Sudbury Basin: the 60\% uncertainty on the signal produced by this lithologic unit plays a crucial role on the discrimination power on the mantle signal as well as on the geoneutrino spectral shape reconstruction, which can in principle provide a direct measurement of the Th/U ratio in the Earth.Comment: 7 pages including 2 figures and 1 table, in XIV International Conference on Topics in Astroparticle and Underground Physics (TAUP 2015) IOP Publishing , published on Journal of Physics: Conference Series 718 (2016) 06200

Radiogenic power and geoneutrino luminosity of the Earth and other terrestrial bodies through time

We report the Earth's rate of radiogenic heat production and (anti)neutrino luminosity from geologically relevant short-lived radionuclides (SLR) and long-lived radionuclides (LLR) using decay constants from the geological community, updated nuclear physics parameters, and calculations of the $\beta$ spectra. We track the time evolution of the radiogenic power and luminosity of the Earth over the last 4.57 billion years, assuming an absolute abundance for the refractory elements in the silicate Earth and key volatile/refractory element ratios (e.g., Fe/Al, K/U, and Rb/Sr) to set the abundance levels for the moderately volatile elements. The relevant decays for the present-day heat production in the Earth ($19.9\pm3.0$ TW) are from $^{40}$K, $^{87}$Rb, $^{147}$Sm, $^{232}$Th, $^{235}$U, and $^{238}$U. Given element concentrations in kg-element/kg-rock and density $\rho$ in kg/m$^3$, a simplified equation to calculate the present day heat production in a rock is: $$h \, [\mu \text{W m}^{-3}] = \rho \left( 3.387 \times 10^{-3}\,\text{K} + 0.01139 \,\text{Rb} + 0.04595\,\text{Sm} + 26.18\,\text{Th} + 98.29\,\text{U} \right)$$ The radiogenic heating rate of Earth-like material at Solar System formation was some 10$^3$ to 10$^4$ times greater than present-day values, largely due to decay of $^{26}$Al in the silicate fraction, which was the dominant radiogenic heat source for the first $\sim10$ Ma. Assuming instantaneous Earth formation, the upper bound on radiogenic energy supplied by the most powerful short-lived radionuclide $^{26}$Al ($t_{1/2}$ = 0.7 Ma) is 5.5$\;\times\;$10$^{31}$ J, which is comparable (within a factor of a few) to the planet's gravitational binding energy.Comment: 28 pages, 6 figures, 5 table

Perceiving the crust in 3D: a model integrating geological, geochemical, and geophysical data

Regional characterization of the continental crust has classically been performed through either geologic mapping, geochemical sampling, or geophysical surveys. Rarely are these techniques fully integrated, due to limits of data coverage, quality, and/or incompatible datasets. We combine geologic observations, geochemical sampling, and geophysical surveys to create a coherent 3-D geologic model of a 50 x 50 km upper crustal region surrounding the SNOLAB underground physics laboratory in Canada, which includes the Southern Province, the Superior Province, the Sudbury Structure and the Grenville Front Tectonic Zone. Nine representative aggregate units of exposed lithologies are geologically characterized, geophysically constrained, and probed with 109 rock samples supported by compiled geochemical databases. A detailed study of the lognormal distributions of U and Th abundances and of their correlation permits a bivariate analysis for a robust treatment of the uncertainties. A downloadable 3D numerical model of U and Th distribution defines an average heat production of 1.5$^{+1.4}_{-0.7}$$\mu$W/m$^{3}$, and predicts a contribution of 7.7$^{+7.7}_{-3.0}$TNU (a Terrestrial Neutrino Unit is one geoneutrino event per 10$^{32}$ target protons per year) out of a crustal geoneutrino signal of 31.1$^{+8.0}_{-4.5}$TNU. The relatively high local crust geoneutrino signal together with its large variability strongly restrict the SNO+ capability of experimentally discriminating among BSE compositional models of the mantle. Future work to constrain the crustal heat production and the geoneutrino signal at SNO+ will be inefficient without more detailed geophysical characterization of the 3D structure of the heterogeneous Huronian Supergroup, which contributes the largest uncertainty to the calculation.Comment: 25 pages, 9 figures, 6 table

Geoneutrinos from the rock overburden at SNO+

SNOLAB is one of the deepest underground laboratory in the world with an overburden of 2092 m. The SNO+ detector is designed to achieve several fundamental physics goals as a low-background experiment, particularly measuring the Earth's geoneutrino flux. Here we evaluate the effect of the 2 km overburden on the predicted crustal geoneutrino signal at SNO+. A refined 3D model of the 50 χ 50 km upper crust surrounding the detector and a full calculation of survival probability are used to model the U and Th geoneutrino signal. Comparing this signal with that obtained by placing SNO+ at sea level, we highlight a 1.4+1.8-0.9 TNU signal difference, corresponding to the ∼5% of the total crustal contribution. Finally, the impact of the additional crust extending from sea level up to ∼300 m was estimated

Studies of MCP-PMTs in the miniTimeCube neutrino detector

This report highlights two different types of cross-talk in the photodetectors of the miniTimeCube neutrino experiment. The miniTimeCube detector has 24 $8 \times 8$-anode Photonis MCP-PMTs Planacon XP85012, totalling 1536 individual pixels viewing the 2-liter cube of plastic scintillator

Political Branding: The Tea Party and Its Use of Participation Branding

The emergence of the Tea Party movement in 2009 witnessed the surfacing of a populist, anti-Obama libertarian mobilization within the United States. The Tea Party, a movement that brought together a number of disparate groups—some new, some established—utilized participation branding where the consumer attributed the movement its own identity and brand. Its consumer-facing approach, lack of one single leader, and lack of a detailed party platform, in combination with its impact on the 2010 election races in America, earmarks it as a contemporary and unconventional brand phenomenon worthy of investigation. Copyright © Taylor & Francis Group, LLC