Summary
We have analysed the reaction -p ;n→π−π+π− between 2.08 and 2.29 GeV c.m. energy. The population of the 3π Dalitz plot (a total of 2328 events at all energies) is strongly nonuniform and shows a structure that can be qualitatively interpreted with simple Veneziano-type formulae. The moments of the angular distributions of the three-pion plane are also examined.
Riassunto
La reazione -p ;n→π+π−π− è stata analizzata nell’intervallo di energia nel baricentro da 2.08 a 2.29 GeV. La popolazione del diagramma di Dalitz (per un totale di 2328 eventi a tutte le energie) mostra forti disuniformità e strutture che possono essere interpretate qualitativamente con semplici formule alla Veneziano. Si sono inoltre analizzati i momenti delle distribuzioni angolari del piano dei tre pioni.
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References
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For higher spins there are as many amplitudes as there are independent tensors taking into account Bose statistics that can be written in terms of the pion momenta.L andM are the powers of the negative pions’ momenta as used byGoebel et al.
The parameters for the real part of the trajectory are determined as explained above; the coefficient of the imaginary part is approximately equal to that used byLovelace. We note that the agreement of the « theory » with the data is not very sensitive to the values of the parameters; for example with the trajectory function used byLovelace (8) and almost equally good fit is obtained.
This has been found to be the case in similar processes. See for example:B. Petterson andN. A. Törnqvist:Nucl. Phys.,13 B, 629 (1969);N. A. Törnqvist: CERN preprint, TH 1094 (1969);Chan Hong-Mo, R. O. Raitio, G. H. Thomas andN. A. Törnqvist:Nucl. Phys.,19 B, 173 (1970);Aachen-Berlin-CERN-London-Vienna Collaboration: CERN preprint/D. Ph. II/Phys. 70-3 (1970) and the review articlesChan Hong-Mo: CERN preprint TH 1057 and TH 1089 (1969);C. Lovelace: CERN preprint TH 1123 (1969).
We have used the program FOWL (F. James: FOWL,a general Monte Carlo phasespace program (unpublished)) and the routine written byJ. F. L. Hopkinson to compute theB5 amplitude (J. F. L. Hopkinson: DNPL/P21, submitted toNucl. Phys.).
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Bettini, A., Cresti, M., Mazzucato, M. et al. The annihilation -p ;n→π+π−π− between 1.0 and 1.6 GeV/c and its comparison with the veneziano model. Nuov Cim A 1, 333–344 (1971). https://doi.org/10.1007/BF02722674
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DOI: https://doi.org/10.1007/BF02722674