The branching ratios of negative pions and protons due to the weak decays of~C and~'B hypernuclei were measured. The negative pionic decay rates (I' -), proton-induced nonmesonic decay rates (I'"), total nonmesonic decay rates (I "), and ratios of the An~nn process to the Ap~pn process (I'"/I' ) were derived from the present measurements combined with previous studies on the mesonic m and total decay rates. The measured Ishows that Pauli blocking is less effective than expected due to pion distortion. We found that I " is nearly equal to unity in units of the free-space A-decay width. The present results also indicate that I " is almost twice that of I . This is in disagreement with calculations based on meson-exchange models in which I " is strongly suppressed.PACS number(s): 21.80.+a, 25.80.Hp
Cascade hypernuclei have been studied in the (K Ϫ ,K ϩ) reaction on a scintillating fiber target. The experimental result is compared with a theoretical calculation in order to extract information concerning the ⌶ Ϫ nucleus potential. ͓S0556-2813͑98͒01108-X͔
At the Hyogo Ion Beam Medical Center (HIBMC) we have developed a new design method for the bar ridge filter used in proton therapy, taking into consideration the scattering and nuclear interaction effects within the filter itself, which are introduced in the design. In our beam delivery system, the bar ridge filter is employed as the range modulator. It is combined with the wobbler system, and produces a three-dimensionally uniform spread-out Bragg peak (SOBP). The design program predicts the three-dimensional dose distribution. Ridge filters of 3-12 cm SOBP in 1 cm increments were designed in the maximum radiation field for 150 MeV and 190 MeV proton beams so that a uniform physical dose area is obtained in the SOBP region three-dimensionally. Measurements were performed with the constructed ridge filters to verify the uniformity and these were compared with the predictions of the design program. The predictions and measurements were found to be in agreement except for the 12 cm SOBP. The uniformities were better than +/- 3.0% for all SOBPs produced. The ridge filters are now clinically in use.
The precise conversion of CT numbers to their electron densities is essential in treatment planning for hadron therapy. Although some conversion methods have already been proposed, it is hard to check the conversion accuracy during practical therapy. We have estimated the CT numbers of real tissues by a calculational method established by Mustafa and Jackson. The relationship between the CT numbers and the electron densities was investigated for various body tissues as well as some tissue-equivalent materials used for a conversion to check the accuracy of the current conversion methods. The result indicates a slight disagreement at the high-CT-number region. A precise estimation of the multiple scattering, nuclear reaction and range straggling of incident particles has been considered as being important to realize higher-level conformal therapy in the future. The relationship between these parameters and the CT numbers was also investigated for tissues and water. The result shows that it is sufficiently practical to replace these parameters for real tissues with those for water by adjusting the density.
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