Browsing by Author "White, Joseph LaSalle"

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    Measurement of the analyzing power in inclusive, high-x(F) charged pion production with a 200 GeV/c polarized proton beam
    (1991) White, Joseph LaSalle; Roberts, Jabus B.
    The analyzing power, A$\sb{\rm N},$ in inclusive $\pi\sp{+}$ and $\pi{-}$ production by a 200 GeV/c polarized proton beam was found to have a striking $x\sb{F}$ dependence in which the magnitude of A$\sb{\rm N}$ increases from 0 to 0.42 for the $\pi\sp{+}$ data and decreases from 0 to $-0.38$ for the $\pi\sp{-}$ data for increasing $x\sb{F}$ over the kinematic range $0.2 \le x\sb{F} \le 0.9$ and 0.2$GeV/c \le p\sb{T} \le 2.0GeV/c.$ The higher values of $x\sb{F}$ and $p\sb{T}$ in these kinematic ranges insure that the measured particle came from an interaction of the beam and target through a direct channel and that quark scattering through gluon exchange is the dominant interaction. The charged pions were identified and tracked with a large forward multi-particle spectrometer based upon a Helium gas threshold Cherenkov counter. A simple parton recombination model correctly predicts the signs of the spin parameters measured in this experiment. It also correctly predicts the magnitudes of the $\pi\sp{+}$ and $\pi\sp\circ$ analyzing power at high $x\sb{F}$ but the $\pi\sp{-}$ analyzing power is twice the predicted value. The $\pi\sp{+},$ $\pi\sp{-},$ and $\pi\sp\circ$ analyzing powers were also measured with a polarized anti-proton beam. These data and their interpretation with the simple model suggest that the transverse spin of the proton can be correlated with its quarks in certain kinematic regions, however, the details are still not well understood.
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    Measurement of the analyzing power in inclusive, high-x(F) neutral pion production at 185 GeV/c
    (1989) White, Joseph LaSalle; Roberts, Jabus B.
    The analyzing power, A, in inclusive $\pi\sp0$ production by a polarized proton beam at 185 GeV/c was found to be 0.10 $\pm$ 0.03 for $\langle$x$\sb{\rm F}\rangle$ = 0.52 and $\langle$p$\sb{\rm T}\rangle$ = 0.8 Gev/c. The $\pi\sp0$'s were detected using a combined lead-glass, lead-scintillator photon absorption calorimeter constructed at the Bonner Lab. Using a simple parton recombination model applied to spin parameter measurements, A$\sb{\rm N}$ = 0.19 $\pm$ 0.02 for this reaction. Since the measured A is consistent with this model, it suggests that the leading quark in a high energy scattering reaction retains the transversity of the incident proton. This can be generalized to suggest that a valence quark model can be used to describe the spin of the proton in certain kinematic regions. A polarized antiproton beam was also produced and A was observed to be nonzero but with low statistics due to short running time. These results show that spin effects continue to be present and have importance at the highest measured energies.