HPC Yearbook 19/20


High-Performance Computing 2019-20


Katrin cuts neutrino mass estimate


Researchers from Europe and the US have finalised research which reduces the mass estimate for the neutrino by 50 per cent, writes Robert Roe


A


n international team of scientists that includes researchers at the Department of Energy’s Lawrence Berkeley National


Laboratory and the Karlsruhe Institute of Technology (KIT), Germany have announced a breakthrough in research which aims to measure the mass of the neutrino, one of the most abundant yet elusive elementary particles in the universe. Te Karlsruhe Tritium Neutrino


(Katrin) experiment, housed at the Tritium Laboratory Karlsruhe, on the KIT Campus North site, is investigating the most important open issue in neutrino physics: what is the absolute mass scale of neutrinos? At the 2019 Topics in Astroparticle and


Underground Physics conference in Toyama, Japan, leaders from the Katrin experiment reported in September that the rest mass of the neutrino is not larger than 1 electron volt, or eV. Tese inaugural results, obtained earlier this year by the Katrin experiment, cut the mass range for the neutrino by more than half, by lowering the upper limit of the neutrino’s mass from 2eV to 1eV.


‘Tese findings by the Katrin


collaboration reduce the previous mass range for the neutrino by a factor of two, place more stringent criteria on what the neutrino’s mass actually is, and provide a path forward to measure its value definitively,’ said Hamish Robertson, a Katrin scientist and professor emeritus of physics at the University of Washington. ‘Knowing the mass of the neutrino will


allow scientists to answer fundamental questions in cosmology, astrophysics and particle physics, such as how the universe evolved, or what physics exists beyond the Standard Model’ of particle physics, Robertson added. Te Katrin experiment involves


researchers at 20 research institutions around the globe. Berkeley Lab’s Katrin team is led by Alan Poon, deputy director of the lab’s nuclear science division. Poon noted that Berkeley Lab’s low


background facility, which measures very-low levels of natural radioactivity in materials, was used to certify the high-purity materials used in Katrin’s components and ensure minimal interference with the experiment. Berkeley Lab’s supercomputing resources also aided in Katrin simulations and data analyses. ‘Our Berkeley Lab team applied our


expertise in materials testing and data analysis to help validate this important measurement,’ Poon said. Neutrinos are one of the most common


fundamental particles in our universe, second only to photons. Yet neutrinos are elusive. Tey are neutral particles with no charge. Tey interact with matter only through the aptly named ‘weak interaction,’ which means that opportunities to detect them and measure their mass are both rare and difficult. ‘If you filled the solar system with lead


out to 50 times beyond the orbit of Pluto, about half of the neutrinos emitted by the sun would still leave the solar system without interacting with that lead,’ Robertson said. Neutrinos are also mysterious particles


Te spectrometer for the Katrin experiment, as it works its way through the German town of Eggenstein-Leopoldshafen in 2006 on its way to the nearby Karlsruhe Institute of Technology


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that have shaken up our understanding of physics, cosmology and astrophysics. Te


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