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Probing the strange nature of the nucleon with phi photoproduction

Description: The presence inside the nucleon of a significant component of strange-antistrange quark pairs has been invoked to explain a number of current puzzles in the low energy realm of QCD. The {sigma} term in {pi}N scattering is a venerable conundrum which can be explained with a 10%--20% admixture. The spin crisis brought on by the EMC result and follow on experiments was first interpreted as requiring a large strange content of s quarks whose spin helped cancel the contribution of the u and d quarks to the nucleon spin, again of order 10%. Excess phi meson production in p{anti p} annihilation at LEAR has also been explained in terms of up to a 19% admixture of s{anti s} pairs. Charm production in deep-inelastic neutrino scattering would appear to provide evidence for a 3% strange sea. It is clear that a definite probe of the strange quark content would be an invaluable tool in unraveling a number of mysteries. The longitudinal beam target asymmetry in {psi} photoproduction is a particularly sensitive probe of that content. It is explored here.
Date: March 6, 1997
Creator: Lowry, M.M.
Partner: UNT Libraries Government Documents Department

A portable cryostat for the cold transfer of polarized solid HD targets: HDice-I

Description: A device has been developed with moveable liquid nitrogen and liquid helium volumes that is capable of reaching over two meters into the coldest regions of a cryostat or dilution refrigerator and reliably extracting or installing a target of solid, polarized hydrogen deuteride (HD). This Transfer Cryostat incorporates a cylindrical neodymium rare-earth magnet that is configured as a Halbach dipole, which is maintained at 77 K and produces a 0.1 T field around the HD target. Multiple layers provide a hermetic 77 K-shield as the device is used to maintain a target at 2 K during a transfer between cryostats. Tests with frozen-spin HD show negligible polarization loss for either H or D over typical transfer periods. Multiple target transfers with this apparatus have shown an overall reliability of about 95% per transfer, which is a significant improvement over earlier versions of the device.
Date: February 1, 2014
Creator: Bass, Christopher D.; Sandorfi, Andy M.; Bade, C.; Blecher, M.; Caracappa, A.; D'Angelo, A. et al.
Partner: UNT Libraries Government Documents Department