Superallowed Fermi beta decay

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Within the realm of particle physics the description of nature on the submicroscopic scale has evolved into the so-called Standard Model. This is a set of rules which specifies the basic constituents of our Universe and the forces that act between them. At ISAC, studies of the decay of radioactive isotopes are being pursued to obtain a better understanding of these fundamental forces in nature. Most radioactive isotopes decay by the simultaneous emission of two energetic particles a beta (i.e. an electron) and a neutrino. Our present understanding of the weak interaction (the force that causes nuclear beta decay) predicts that for a very few special isotopes the decay properties should be identical and related in a simple way to the vector component of the weak force. Precision measurements of the decay rate for these so-called superallowed Fermi beta decays can be used to test this hypothesis and to determine the strength of the force. The current world data on superallowed Fermi beta decay leads to a result that provides one of the most precise tests of the Standard model. However, this result also depends on small but very important corrections that must be computed before the test can be applied. The TRIUMF-ISAC facility provides beams of these special radioactive isotopes over a wider mass range than was previously available. This allows us to further test the model and to validate the corrections that must be applied.