Solar Neutrinos: Theory

Abstract

The solar neutrino problem can be stated simply. The observed capture rate is [1,2]:

$$ Observed = \left( {2\pm 0.3} \right)SNU $$

(1)

The predicted capture rate for the ³⁷Cl experiment is [3,4]:

$$ \Pr edicted = \left( {7.5\pm 2.5} \right)SNU $$

(2)

[The convenient unit for discussing solar neutrinos is the product of a flux times a cross section and is: 1 SNU = 10^-36 events per target particle per second. I give here preliminary values of event rates predicted by the standard solar model that have been obtained by an improved set of calculations with updated parameters. The final values will be published in reference 4.] The observational error quoted above is 1-σ(by tradition); the error I quote on the predicted rate corresponds to an effective 3-σ auncertainty, defined in [3]. The fact that the theoretical and the experimental numbers differ significantly is the solar neutrino problem. There is no generally accepted solution to the problem although neutrino oscillations in matter provides a plausible and attractive hypothesis [5,6].