Text: Hyperons and Neutrinos http://conferences.fnal.gov/tevft/book/SECTION7.htm In the beginning, at Fermilab, there were neutrinos and hyperons created by beams from the Main Ring. Among the first experiments proposed, approved, and run were E1A, and E21, the first generation of Fermilab electronic neutrino detectors, and E8 the first generation Fermilab hyperon beam experiment. There were also several bubble chamber exposures in the neutrino beam. These approaches matured into complete programs of experiments in the Tevatron fixed target era. The common physics thread shared by these two rather different beam particles is the weak interaction. Neutrinos are particles which feel only the weak force. This makes them excellent probes of complicated structures, like protons and neutrons. Some of the Tevatron neutrino experiments were so sharply focused in the area, that they have been included in the section on proton, neutron, and meson structure rather than here. Neutrinos are also excellent places to study the weak interaction itself. They don¹t do anything else, so they are a clean weak interaction laboratory. Neutrino scattering cross-sections (the probability that they will actually hit something in a given target) increase linearly with the neutrino energy. This made the 400 GeV Fermilab Main Ring good for doing neutrino physics, and the 800 GeV/c Tevraton even better. The hyperons are the particles in the same family as the proton and the neutron, but containing one or more strange valence quarks. Only the weak interaction does not conserve strangeness; it is the only way a hyperon can decay. This makes hyperons live 1014 times longer than their non-strange cousins, the excited non-strange proton and neutron states. This is long enough to make hyperon beams that will go many meters at Tevatron energies before most of the hyperons decay. Hyperons, like protons, are particles of spin 1/2. This makes it possible to have polarized hyperon beams; something which is impossible with a spin 0 K meson beam. Polarization is a delicate and sensitive probe of both the weak interaction controlling the hyperon¹s decay and the structure of the quarks and other stuff which makes up the hyperon itself. E8 discovered in 1976 that hyperons were produced with significant polarization. Tom Devlin, of Rutgers University, and Lee Pondrom, of the University of Wisconsin, were subsequently awarded the Panofsky prize for this discovery and the sequence of experiments it enabled. Typically only one process happens at a time in weak interactions, one quark decays to another, or a neutrino hits just one quark in a target proton. The combination of the cleanliness of the weak interaction and the high intensity beams of both neutrinos and hyperons available at the Tevatron allowed a set of experiments of unprecedented precision. A carefully crafted experiment can isolate just one particular aspect of the structure of a proton in order to study it carefully. For example, the E632 dimuon result focused in on the charmed quark content of the proton - which only exists in the sea of virtual quark antiquark pairs inside the proton. In a similar but different example, in a series of experiments all the hyperon magnetic moments were measured with high precision, including the W- (by E800) which is made of three strange valence quarks. The results are sufficiently precise to both confirm our basic understanding of the structure of the baryons (the family to which protons, neutrons and hyperons belong) and to confound theoretical description anywhere close to the present experimental uncertainties. E815/NuTeV will make a precision measurement of the Weinberg angle, sin2(qW), a fundamental electro-weak parameter more normally associated with the very high energy scales of e+e- and hadron colliders. E872 is seeking to observe the last fundamental fermion, the t neutrino.

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