The International Society for Optics and Photonics
CREOL, The College of Optics & Photonics
The mission of SPIE Student Chapter is to advance an interdisciplinary approach to the science and application of light and provide professional development opportunities for UCF students.

SPIE Student Chapter Faculty Talk Series: "Tiny neutral ones – neutrinos" by Dr. Michael Bass

Celebrating the International Year of Light 2015

Abstract: The idea that there had to be a particle that was very small, did not carry charge, could be massless, had spin ½ , and took part in beta decay was introduced by Wolfgang Pauli and elaborated on by Enrico Fermi in the early 1930s.  They needed such a particle to save energy, linear and angular momentum conservation in beta decay.  It was found experimentally in 1955.  These neutrinos were associated with electrons. Then things became more complicated and there seemed to be neutrinos associated with the newly discovered muon and tau particles.  Theorists speculated that perhaps these different neutrinos were different eigenstates of one particle (sometimes called different flavors) and therefore the neutrino would have to have mass.  It would be very little mass but still some mass.  Experiments discovered the muon and tau neutrinos.  Nobel prizes were awarded and still the question of neutrino mass remained unanswered.  If the neutrino had mass it would change type or flavor and it would not move at the speed of light.  The work led by Takaaki Kajita and Arthur B. McDonald demonstrated clearly that neutrinos did change flavor and hence had mass.  For that they won the 2015 Nobel Prize in Physics. 

An interesting aside:  From their work and careful analysis it is clear that the total mass of the three neutrinos cannot exceed 10-6 of an electron mass or 10-9 of a proton mass.  This is what it must be if stars are to experience nuclear fusion and beta decay to evolve and live long enough to produce the higher atomic number atoms that make up us. 

Biography: Michael Bass received his PhD in Physics from the University of Michigan and is Professor Emeritus of Optics at UCF. His current research interests are in modeling high power optically pumped, solid-state lasers, thermal management of high power diode laser pump sources, the use of volume Bragg gratings in solid state laser resonators, and novel, all optical two and three dimensional displays. Dr. Bass is a Fellow of both the Optical Society of America and the IEEE.

Posted Friday, October 23, 2015

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