Browsing by Author "Taylor, Simon John"
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Item Radiative decays of low-lying excited-state hyperons(2000) Taylor, Simon John; Mutchler, Gordon S.The quark wave-functions of the lower-lying excited-state hyperons Λ(1405), Λ(1385), and Λ(1520) are not well understood. For example, the Λ(1405) may not be a regular three-quark state but K¯N molecule. Several competing models have been proposed, but none have been convincingly eliminated. Measuring radiative decays provides a means of discriminating between the models. The radiative branching ratios are predicted to be small (∼1%), but the radiative widths vary by factors of 2--10 from model to model. The existing experimental data is sparse and inconsistent; moreover, the radiative decay of the Sigma(1385) has never been observed before (except for one event). These lower-lying excited-state hyperons were produced in a tagged photon-beam experiment in the CLAS detector at TJNAF in the reaction gammap → K+Y* for photon energies from threshold to 2.4 GeV. The radiative branching ratio for the Sigma0(1385) relative to the Sigma0(1385) → Sigmapi0 channel was measured to be 0.021 +/- 0.008+0.004-0.007 corresponding to a partial width of 640 +/- 270+130-220 keV.Item Scintillation detector development for the solenoidal tracker at RHIC (STAR) and the CEBAF large acceptance spectrometer (CLAS)(1996) Taylor, Simon John; Mutchler, Gordon S.After a brief introduction describing some of the physics and mechanics of scintillation detection, results of the development for the Central Trigger Barrel (CTB) for STAR and the Start Counter for CLAS are discussed. For the CTB development, 1 cm x 20 cm x 100 cm scintillators were studied with light guides of various geometries and materials attached to one end in order to optimize the uniformity and overall gain. The best results were obtained using a 61$\sp\circ$ OP-1 light guide attached to a BC 408 scintillator. An alternate approach using a wavelength shifter produces much lower pulse heights than the other method. The CEBAF scintillators are intended to enclose the target area in order to identify the beam bucket for a particular event with timing resolution of 350 ps or less. Single paddle and coupled-paddle approaches are discussed. The coupled-paddle approach meets the design goals.