Neutrino Mass: Sentence Outline
Abstract. Long assumed to be massless, the
ubiquitous yet ghostly neutrino may have some substance after all.
After a brief introduction to the tiny subatomic particle, I discuss
two popular methods of measuring its mass: direct measurement and
indirect via detection of so-called "neutrino oscillations." Promising
claims of nonzero mass from indirect measurements are presented, along
with implications for particle physics, solar dynamics, and the
ultimate fate of the universe.
- "Invented" in 1930 by Wolfgang Pauli to account for energy
seemingly lost in the neutron decay process, the neutrino long evaded
- Pauli assumed a precisely zero neutrino mass. Testing this
assumption is even harder than detecting a neutrino, primarily because
the mass is zero or almost zero.
- While direct approaches remain severely limited, indirect
measurement has made substantial progress recently by successfully
detecting the phenomenon called neutrino "mixing" or "oscillation" 
- The principle seems clear enough theoretically, but how can these
oscillations be detected in practice?
- Measuring a nonzero mass is significant for several reasons, not
least of which is simply that particle physicists have assumed the contrary
- The idea of neutrino oscillations, long thought to be only of
theoretical interest but now apparently vindicated by experiments, has
carried mass measurements beyond conventional approaches.
 David Griffiths, Introduction to Elementary Particles (Wiley, New
York, 1987), pp. 22-28.
 John Learned, "Discovery of Neutrino Oscillations and Mass" (Online:
http://www.phys.hawaii.edu/,jgl/neutrino news.html), June 1998.
 Wick C. Haxton and Barry R. Holstein, hep-ph/9905257, (1999).