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Unformatted text preview: HW 4 Phys5405 f07 due 10/4/2007 This assignment will illustrate the use of relativistic kinematics by looking at some of the reactions and decays pertinent to my current research project. The goal is to measure the branching ratio for + to decay into e + rather than + , with much improved accuracy, BR = e + e + . (1) The current standard model of particle physics and cosmology calculates this ratio with an accuracy < . 05%, while the experimental accuracy is at the 0 . 4% level. If the experimental accuracy can be improved by about an order of magnitude a exceptionally sensitive test of the standard model results. 1) So first lets create the . This is usually done at a proton accelerator. For a fixed target, say a neutron in a nucleus, the reaction, neglecting neutron binding energy, would be, p + n n + n + + . (2) Given that the rest energies of the p, n, and = 938.0, 939.5, and 139.6 MeV, what is the minimum KE(p) required to produce the...
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