LANL Scientists’ Link To 2015 Nobel Prize In Physics

LANL News:

Los Alamos National Laboratory scientists played a significant role in the research that led to the awarding of the 2015 Nobel Prizes in Physics to Arthur McDonald, head of the Sudbury Neutrino Observatory (SNO) in Canada and Takaaki Kajita of Japan, head of the Super-Kamionkande (Super K) experiment, for their work in discovering that neutrinos have mass.

The LANL Connection

LANL was instrumental in the design, assembly and data analysis of the SNO experiment. More than 20-plus years—from the start of funding in 1990 to its final results in 2012—more than 30 LANL scientists and technicians were involved in the SNO collaboration. One of LANL’s major contributions was the development and assembly of the neutral current detector (NCD) array that operated from 2003 to 2006 in SNO that made an independent measurement of the total solar neutrino flux, which in turn confirmed its previous result that neutrinos have mass and change type between the sun and earth. 

LANL also played major roles in delivering low-background photomultiplier tubes for the experiment, in the creation of a number of custom calibration sources that were used to calibrate the detector, and in data acquisition software and data analysis and simulations. 

In addition, two current LANL scientists contributed to the Super-K experiment.  Christopher Mauger had a significant role in the calibration and simulation of the detector and received his PhD from Stony Brook University on neutrino oscillations.  Todd Haines worked on Super-K’s veto system, calibrations and analysis.  He started his work at the University of Maryland and continued it while an Oppenheimer Fellow at LANL.

Understanding Neutrinos

Neutrinos are one of the most numerous particles in the entire universe, second only to particles of light. There are three types of neutrinos: electron, muon and tau. Most neutrinos that make it to Earth come from the sun, but others come from cosmic rays, exploding stars, the center of the Earth, nuclear power plants and even nuclear processes within our bodies. They are neutral and rarely interact with other matter. In fact, thousands of trillions of neutrinos pass through our bodies each second. 

Prior to McDonald and Kajita’s discovery, neutrinos were thought to be massless. In the 1960s, scientists studying neutrinos from the sun were detecting only a third of the number of particles they expected to see.  This deficit led to speculation as to the cause of the discrepancy. Some thought it might be the result of faulty theoretical calculations; some wondered if there were problems with the experiment itself; and others thought that the neutrinos might be changing identity as they travelled from the Sun to the Earth.  McDonald and Kajita proved that the reason for the deficit was that the neutrinos were changing identity: from electron-neutrinos (which is the only type produced by the sun) to muon- or tau-neutrinos as they reached Earth. Why is this so significant? Because to change identity the neutrinos must have mass.  

“This discovery fundamentally changed our understanding of matter,” said Keith Rielage, a particle astrophysicist at Los Alamos National Laboratory who contributed heavily to the data analysis from the NCD phase of the experiment. “Knowing that neutrinos have mass allows us to better understand how the universe formed the way it did, leading to galaxies and stars, and even us. Neutrinos are very hard particles to study since they interact so infrequently, so the fact that this research was done and done successfully is a major accomplishment and gives us hope as we look for other particles like dark matter that is even harder to study.”

LANL Contributors

Both current and past LANL scientists and technicians contributed to the research.

Current LANL employees who contributed to SNO:

Tom Bowles, Michael Browne, Steve Elliott, Ernst Esch, Mac Fowler, Kate Frame, Keith Rielage, Laura Stonehill and Richard Van de Water.

Past LANL employees who contributed to SNO:

J. Manuel Anaya, Joe Banar, Steve Brice, Mark Boulay, Tom Burritt, Peter Doe, Emily-Michael Dragowsky, Noel Gagnon, Joe Germani, Azriel Goldschmidt, Andre Hamer (deceased), Jaret Heise, Andrew Hime, Klaus Kirch, Geoff Miller, Stan Seibert, Hardy Seifert, Miles Smith, Hamish Robertson, Nikolai Starinsky, Peter Thornewell, Jerry Wilhelmy, John Wilkerson and Jan Wouters (deceased).

Current LANL employees who contributed to Super-K:

Christopher Mauger, Todd Haines.

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