Summary
The reaction π−+d → 2n+ϒ for zero-energy pions has been studied in a deuterium bubble chamber by observing the electron pairs produced by the internal conversion of the photons. The energy partition and mass distributions of the pairs are in agreement with the theory of Kroll and Wada. The energy spectrum was compared with the calculations of Joseph to find the effect of the neutron-neutron interaction. Satisfactory agreement is obtained if the singlet scattering lengtha s is less than — 10 fermi. The branching ratio σ(π−+d → 2n)/σ(π−+d → 2n+ϒ) was found to be 2.89±0.09. The pion photoproduction cross-section was calculated from this to be (0.110±0.022)η mb, in contrast to the directly measured value of (0.197±0.014)η mb. The reaction π−+d → 2n+π0 was not seen; the fraction of captures which go through this channel is less than 0.07%.
Riassunto
Si è studiata la reazione π−+d → 2n+ϒ per pioni di energia nulla in una camera a bolle di deuterio, osservando le coppie di elettroni prodotte per conversione interna dei fotoni. La ripartizione dell’energia e le distribuzioni delle masse concordano con la teoria di Kroll e Wada. Si è confrontato le spettro d’energia con i calcoli di Joseph per cercare l’effetto della interazione neutrone-neutrone. Si ottiene un’accordo soddisfacente se la lunghezza di scattering del singolettoa s è inferiore a — 10 fermi. Si è trovato che il rapporto di suddivisione σ(π−+d → 2n)/(σ(π−+d → 2n+ϒ) è 2.89±0.09. Da questo si è calcolato che la sezione efficace per la fotoproduzione di pioni è (0.110±0.022)η mb, in contrasto col valore direttamente misurato (0.197±0.014)η mb. Non si è osservata la reazione π++d → 2n+π0; la frazione di catture che passano per questo canale è inferiore a 0.07%.
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Submitted as a thesis to the Department of Physics of the University of Chicago in partial fulfillment of requirements for the Ph. D. degree.
Research supported by a joint program of the Office of Naval Research and the National Science Foundation.
The bubble chamber used was that designed byR. H. Hildebrand, who directed its operation during the cyclotron runs with the help ofE. H. Denton, S. Lucero, J. H. Doede andR. M. Handler. Earlier work to improve the operation of the bubble chamber and its equipment was done byH. G. E. Kobrak andM. A. Pyka. The film was scanned by two groups, one under the supervision of Mrs.K. Richey, the other organized byJ. Berryhill and directed byR. L. Weiss, who also were responsible for the measuring. Measuring was done on the table designed byS. D. Warshaw and built and serviced byL. Seefeldt. Several helpful conversations were held withV. L. Telegdi.
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Kloeppel, P.K. Interactions of stopping negative pions with deuterium. Nuovo Cim 34, 11–26 (1964). https://doi.org/10.1007/BF02725865
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DOI: https://doi.org/10.1007/BF02725865