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ANTIPROTON ANNIHILATIONS IN COMPLEX NUCLEI

Journal Article · · Nuclear Phys.
; ; ;

BS>An investigation of 356 antiproten annihilations ia nuclear emulsion is reported. The results are generally analyzed to yield information on primary processes, assumed to be annihilations with single protons or neutrons into a number of pions with or without a K-meson pair. The average pion multiplicity is 4.68 plus or minus 0.12 for annihilations at rest and 5.11 plus or minus 0.12 for annihilations in flight (the antiproton energy being on the average of 166 Mev). This increase of 0.4 plus or minus 0.2 pion is to be compared with an expected average increase of 0.1 pion. The pion energy distributions are given with mean values of 391 plus or minus 10 Mev total energy (at rest) and 390 plus or minus 9 Mev (in flight). Emission of K-meson pairs is found to take place in 3 plus or minus % of the annihilation reactions. The average number of pions emitted together with K-mesons is 2.2 plus or minus 0.5. The correction for K-meson pairs unobservable in usual emulsion experiments has been computed. The result that about 40% of the K-meson pairs are undetectable means that the correction for detection efficiency is larger than previoualy assumed. A recalculation of all published duta using emulsion detecters results in a world average of 5.0 plus or minus 1.1% of the annihilations with K-meson pairs for annihilations at rest and in flight (antiproten energy below 250 Mev). The annihilation probability at rest with neutrons is found te be less than that with protons on the basis of a determination of the number of stars with an odd number of charged pions relative to that with an even number. The odd/even ratio is 0.73 plus or minus 0.09. The reabsorption probability of the pions in complex emulsion nuclei is determined. It is found that, on the average, 18% of the pions at rest and 32% of the pions in flight are abeorbed. The diference is understeed as a result of the movement of the center of momentum and the penetration of the antiprotons into the nuclei for the cases prcduced in flight. Comparison of the experimental results with the predictions of various theories is carried out. For the pion production, however, no decision in favor of a particular theoretical model can be made. As regards the production of K-mesons, all theories fail to predict the experimentally found production frequency. The world data on antiproton annihilations are collected, reanalyzed, and discussed. (auth)

Research Organization:
Univ. of Uppsala; Univ. of Stockholm
NSA Number:
NSA-15-012150
OSTI ID:
4070140
Journal Information:
Nuclear Phys., Journal Name: Nuclear Phys. Vol. Vol: 22
Country of Publication:
Country unknown/Code not available
Language:
English

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Related Subjects

ABSORPTION
ANNIHILATION
ANTIPROTONS
CROSS SECTIONS
DISTRIBUTION
DISTURBANCES
EFFICIENCY
ENERGY
ENERGY RANGE
ERRORS
INTERACTIONS
KAONS
MATHEMATICS
MEASURED VALUES
MOTION
NEUTRONS
NUCLEAR EMULSIONS
NUCLEAR MODELS
NUCLEAR REACTIONS
NUCLEAR THEORY
NUCLEI
NUMERICALS
PAIR PRODUCTION
PARTICLE TRACKS
PHYSICS
PIONS
PRODUCTION
PROTONS
SPECTRA