| Budget Amount *help |
¥1,900,000 (Direct Cost: ¥1,900,000)
Fiscal Year 1986: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1985: ¥1,200,000 (Direct Cost: ¥1,200,000)
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| Research Abstract |
Our group have studied for ( <gamma> , <pi^+> ) reactions on various nuclei since the first publication on angular distribution of photoproduced <pi^+> from <^(12)C> by our group. For ( <gamma> , <pi^-> ) reaction, backgrounds are strong, but we found a possibility for this reaction and have been preparing experiments since 1984. After a little improvement, we completed experiments on <^(13)C> (e, <pi^-> ) and changed the detector from SSD system to MWPC and back counters with a part of the Grant-in aid for Scientific Research. The charcter of this new system has been studied in 1986 and then applied for <^(15)N> (e, <pi^-> ).
The nuclear transitions with <P_(1/2)> <-!>> <P_(1/2)> as for <^(13)C> ( <gamma> , <pi^-> ) <^(13)N_g.s.> and <^(15)N> ( <gamma> , <pi^-> ) <^(15)O_g.s.> show particular interests on a strong contribution of a higher order spin-dependent term in addition to the spin term (Krol Ruderman term) which is always strong, and also on a comparable E0 component which is interesting for nuclear structure study. These two reactions have been measured with <^(13)C> (e, <pi^-> ) and <^(15)N> (e, <pi^-> ) reactions, and the results are used for the derivation of ( <gamma> , <pi^-> ) angular distributions.
The experimental results are compared with the theoretical estimates which have been obtained with active discussions between the theorist and our group members supported by the Grant. For <^(13)C> , the angular distributions are well explained by the theory if we negrect the E0 contribution which concerns <DELTA> effect in nuclei. For <^(15)N> , a large disagreement is found between experimental and theoretical studies. This disagreement should be important, so we are planning further theoretical calculations and experimental confirmation.
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