H. Yuta, University of Rochester Report No. UR-875-271, 1969 (unpublished). 9~ similar calculation performed by F. Bomse and R. Moses, Phys. Rev. 3, 2163 (1968), also predicts a low-mass Kfa enhancement. Also see the analogous work pertaining to the Ai in F. Winkelmann, R. Mickens, and H. J. Lubatti, Nucl. Phys. m, 535 (1971), and in Ref. 3. "'The quantities da/dt jeXp were calculated in the manner described in Ref. 3. "~h e s e values of m a s s and width a r e similar to those which were found to describe the Q + signal produced in 12.7-GeV/c K'p interactions, s e e M. Farber et al., Phys. Rev. D 1, 78 (1970). We have widened the rcE to account for the different widths observed in Fig. 4. When fitting m a s s spectra we use a distorted Breit-Wigner: The simple Breit-Wigner form i s multiplied by the polynomial employed to describe the background.We present results of an energy-dependent phase-shift analysis for aa energies between 550 and 1150 MeV from reactions a+p -n+rr-A++ and a+p -K+K-A++ a t 7.1 GeV/c. The
We present results on vector meson photoproduction via +yp -. Vp in the LBL-SLAC 82" hydrogen bubble chamber exposed to a linearly polarized photon beam at 2.8, 4.7 and 9.3 GeV. We find p" production to have the characteristics of a diffractive process, i.e., a cross section decreasing slowly with energy and a differential cross section with slope of -6.5 GeV -2 . Within errors the p" production amplitudes are entirely due to natural parity exchange. S-channel helicity is conserved to a high degree in the y --+p' transition. We find evidence for small helicity flip amplitudes for 7rr pairs in the ,o" region. Photoproduction of w mesons is separated into its natural (aN) and unnatural (vu) parity exchange contributions. The E -Y and t-dependence and the spin density matrix of the unnatural parity exchange contribution are consistent with an OPE process.The natural parity exchange part has characteristics similar to p" production.At 9.3 GeV the ratio of a@') to aN(w) is -7. The slope of the Q? differential cross section is -4.5 GeVm2, smaller than that of p" and w production. Natural parity exchange is the main contributor to + production. No evidence for higher mass vector mesons is found in 717~~ ~TTT or m final states. The s-and tdependence of Compton scattering as calculated from p, w and 9 photoproduction using VDM agree with experiment, but the predicted Compton cross section is too small by a factor of two.
A cone-beam computed tomography (CT) system utilizing a proton beam has been developed and tested. The cone beam is produced by scattering a 160 MeV proton beam with a modifier that results in a signal in the detector system, which decreases monotonically with depth in the medium. The detector system consists of a Gd2O2S:Tb intensifying screen viewed by a cooled CCD camera. The Feldkamp-Davis-Kress cone-beam reconstruction algorithm is applied to the projection data to obtain the CT voxel data representing proton stopping power. The system described is capable of reconstructing data over a 16 x 16 x 16 cm3 volume into 512 x 512 x 512 voxels. A spatial and contrast resolution phantom was scanned to determine the performance of the system. Spatial resolution is significantly degraded by multiple Coulomb scattering effects. Comparison of the reconstructed proton CT values with x-ray CT derived proton stopping powers shows that there may be some advantage to obtaining stopping powers directly with proton CT. The system described suggests a possible practical method of obtaining this measurement in vivo.
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