April 22, 2016
Colloquium Speaker: Shawn Usman
Mr. Shawn M. Usman is an R&D Scientist at the National Geospatial-Intelligence Agency (NGA). He leads multidisciplinary teams in particle physics research to advance the fields of geophysics and nonproliferation. Most notably, Mr. Usman established a research program to image neutron/antineutrino emissions from radioactive elements. In addition to possible future nonproliferation applications, the research seeks to characterize the planet’s natural radioactivity giving scientists key insights into the composition of the Earth and its associated geodynamics
Mr. Usman attended Purdue University where he completed dual Bachelor of Science degrees in both Physics and Mathematics in 2006. In 2012, he completed his Master of Science degree in Applied Physics from The Johns Hopkins University, Baltimore, Maryland.
Every second greater than 1025 antineutrinos radiate to space from Earth, shining like a faint antineutrino star. Underground antineutrino detectors have revealed the rapidly decaying fission products inside nuclear reactors, verified the long-lived radioactivity inside our planet, and informed sensitive experiments for probing fundamental physics. Mapping the anisotropic antineutrino flux and energy spectrum advance geoscience by defining the amount and distribution of radioactive power within Earth while critically evaluating competing compositional models of the planet. We present the Antineutrino Global Map 2015 (AGM2015), an experimentally informed model of Earth’s surface antineutrino flux over the 0 to 11 MeV energy spectrum, along with an assessment of systematic errors. The open source AGM2015 provides fundamental predictions for experiments, assists in strategic detector placement to determine neutrino mass hierarchy, and aids in identifying undeclared nuclear reactors. We use cosmochemically and seismologically informed models of the radiogenic lithosphere/mantle combined with the estimated antineutrino flux, as measured by KamLAND and Borexino, to determine the Earth’s total antineutrino luminosity at 3.4 +2.3 -2.2 E25 antineutrinos per second. We find a dominant flux of geo-neutrinos, predict sub-equal crust and mantle contributions, with ~1% of the total flux from man-made nuclear reactors.