Evidence for Neutrino Instability

  • F. Reines
Part of the Lie Groups: History, Frontiers and Applications book series (LGR, volume 11)


We report evidence for neutrino instability obtained from the analysis of data taken on the charged and neutral current branches of the reaction
$$ \overline {v_e } + d\left( {\begin{array}{*{20}c} { \nearrow \;n + n + e^ + \;c.c.} \\ { \searrow \;n + p + \overline {v_e } \;n.c.} \\ \end{array} } \right) $$
at 11.2 meters from a 2000 MW Savannah River reactor. Tests of the results show them to be consistent with data on \( \overline {\nu _e } + p \to n + e^ + \) also taken at 11.2 meters and 6.0 meters.

If we assume that, for the low energies involved (< 10 MeV), \( \overline v _e \) reflects contributions from only two neutrino states of masses m1 and m2, then the deuteron data taken by themselves imply limits on \( \Delta = (m_1^2 - m_2^2 ) \) and on sin2 2θ, where θ is the “mixing angle” of Pontecorvo.


Neutrino Oscillation Atmospheric Neutrino Neutrino Flux Reactor Neutrino Single Neutron 
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  1. 1.
    E. Pasierb, H.S. Gurr, J. Lathrop, F. Reines, and H.W. Sobel, Phys. Rev. Lett. 43, 96 (1979). As will emerge from the present discussion, it is more nearly correct to label the neutral current branch as \( {\text{v}}_{{\text{reactor}}} {\text{ + d }} \to {\text{n + p + v}}_{{\text{reactor}}} \).ADSCrossRefGoogle Scholar
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    We wish to thank A. Hahn for pointing out an effect which changed this quantity by about 10%.Google Scholar
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    The positron spectrum from the reaction \( \overline v _e + p \to n + e^ + \) was measured concurrently with the operation of the elastic scattering detector \( {\text{v}}_{{\text{reactor}}} ^{ + e^ - \to } v_{{\text{reactor}}} ^{ + e^ - } \) F. Reines, H.S. Gurr, and H.W. Sobel, Phys. Rev. Lett. 37, 315 (1976). Analysis of this portion of the data is proceeding and will be published elsewhere. Because the elastic scattering of reactor neutrinos is suspected to be sensitive to neutrino instability, we are subjecting our published and subsequent data to careful scrutiny.ADSCrossRefGoogle Scholar
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    We note that the negative results of R. Davis, Phys. Rev. 97, 766 (1955), and private communication (1980) who looked at a nuclear reactor for \( {\text{v + }}^{{\text{39}}} {\text{C1}} \to ^{{\text{37}}} {\text{Ar + e}}^{\text{ - }} \) and saw < 1/50 of that which would be produced if the reactor v were ve, can in the light of the present results be interpreted as ruling against lepton → antilepton oscillation, i.e., \( {\text{v}}_{\text{e}} \ne {\text{v}}_{\text{e}} \) .ADSCrossRefGoogle Scholar
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    An extended discussion of this interesting topic of possible ranges of Δ allowed by the deuteron and other data is in preparation.Google Scholar
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    Data on \( \overline v _e + p \to n + e^ + \) obtained by the California Institute of Technology-Grenoble group at a distance of 8.7 meters from the 57 MW research reactor of Institut Laue-Langevin seems to be consistent with these conclusions. (Private communication, F. Boehm, P. Vogel, April, 1980).Google Scholar
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    A moveable detector designed for this purpose by S.Y. Nakamura, W.R. Kropp, H.W. Sobel, and F. Reines is nearing completion. See also S.Y. Nakamura et al., Contribution to v-76, Aachen.Google Scholar
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    An experiment to study reaction (1) in more detail is under development by a Georgia Tech-University of South Carolina group. In addition to detecting the neutrons they propose to measure as well the energy spectrum of the product protons, so yielding as a function of energy. (T. Ahrens and T.P., Lang, Phys. Rev. C3, 979 (1971); T.P. Lang et al., in Neutrinos 78, É.C. Fowler (ed.), Purdue University, 1978, p. C68).ADSGoogle Scholar
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Copyright information

© Robert Hermann 1980

Authors and Affiliations

  • F. Reines
    • 1
  1. 1.Department of PhysicsUniversity of CaliforniaIrvineUSA

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