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Number 631 #1, April 2, 2003 by
Phil Schewe, James Riordon, and Ben Stein
The First-Ever Large China-Taiwan Scientific
Collaboration
The first-ever large China-Taiwan scientific collaboration has
carried out a reactor experiment which puts a new upper limit on the
neutrino magnetic moment. Consider first the electron; it not only has
electrical charge but also spin, which means that it will act like a
tiny magnet. Even a neutral atom, because of its internal distribution
of negative and positive charge, can have a nonzero magnetic moment.
Consequently neutral atoms can be controlled, to some extent, by
magnetic fields. But what about a neutrino? Neutrinos may well possess a
small amount of mass, But what about magnetism? Can they effectively
have a tiny bit of charge or internal structure? A nonzero neutrino
magnetic moment provides the neutrino with a way to interact
electromagnetically with the world; generally the neutrino is thought to
interact only via the weak nuclear force. Evidence for nonzero magnetic
moment would show up in several ways: in anomalous electron-neutrino
scattering, in radiative decays in which the neutrino casts off a gamma
ray, and in various astronomical settings, such as supernovas. The
TEXONO collaboration, using neutrinos from the 2.9-GW Kuo-Sheng Nuclear
Power Station in Taiwan, looked for a characteristic anomalous electron
energy spectrum arising from electron-neutrino scattering. They did not
see any such evidence, and from this they derive the best
direct-laboratory upper limit on neutrino magnetic moment, 1.3 x
10-10 times the magnetic moment of the electron (a unit also
known as the Bohr magneton). The team also derives an indirect bound
on neutrino radiative decays. (Li et al., Physical Review
Letters, 4 April 2003; contact Henry Wong, Academia Sinica,
Taiwan, 886-2-2789-6789) The TEXONO
Collaboration is supported by several research institutions and their
respective funding agencies from Taiwan and China. An efficient flow of
students and scientists moves in both directions.
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