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Il Nuovo Cimento (1955-1965)

, Volume 39, Issue 2, pp 417–441 | Cite as

The reaction Open image in new window ππ at 3 GeV/c and the production mechanism of Open image in new window

  • M. Ferro-Luzzi
  • R. George
  • Y. Goldschmidt-Clermont
  • V. P. Henri
  • B. Jongejans
  • D. W. G. Leith
  • G. R. Lynch
  • F. Muller
  • J. -M. Perreau
Article

Summary

In a study of the four-particle states K+p→
ππ at 3 GeV/c, it is found that the quasi-two-body process K+p→
* occurs in large proportion. The cross-sections for the various charge and decay modes of K*
* are in good agreement with the predictions based on isotopic-spin invariance. The sharply peaked c.m. production angular distribution suggests peripheralism. Within the framework of a simple one-meson-exchange model the decay angular distributions of K* and
* are consistent with the assumption that the reaction proceeds predominantly through the exchange of a single pion. Such a model is unable to explain the nonzero value of the « interference » parameter Reϱ1, 0 (−0.13±0.02). In addition, the model requires the inclusion of a drasticad-hoc form factor, similar to the one used at 1.96 GeV/c, in order to fit the observed production angular distribution. A modified one-meson-exchange model taking into account the absorption due to competing processes and developped by Jackson, Donohue, Gottfried, Keyser and Svensson, does not explain the absolute value of the cross-section, but predicts, with a minimum of assumptions, a production angular distribution and decay correlations in reasonable accord with experiment.

Riassunto

In uno studio degli stati a quattro particelle K+
a 3 GeV/c si è trovato che il processo di due quasi-corpi K+p→
* avviene in grande proporzione. Le sezioni d’urto per i vari modi di carica e di decadimento del K*
* sono in buon accordo con le predizioni basate sull’invarianza dello spin isotopico. Il forte picco della distribuzione angolare della produzione nel centro di massa suggerisce il periferalismo. Entro lo schema di un semplice modello a scambio di un mesone le distribuzioni angolari del decadimento del K* e del
* sono in accordo con l’ipotesi che la reazione proced a tramite lo scambio di un solo pione. Tale modello non è in grado di spiegare il valore non nullo del parametro di « interferenza » Reϱ1,0 (−0.13±0.02). Inoltre il modello esige che siano introdotti drastici fattori di formaad hoc, simili a quello usato a 1.96 GeV/c per approssimare la distribuzione angolare di produzione osservata. Un modello modificato a scambio di un mesone che tiene conto dell’assorbimento dovuto a processi in competizione, sviluppato da Jackson, Donhue, Gottfried, Keyser e Svensson, non spiega il valore assoluto della sezione d’urto, ma predice, con un minimo di ipotesi, una distribuzione angolare di produzione e delle correlazioni di decadimento in ragionevole accordo con l’esperienza.

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Copyright information

© Società Italiana di Fisica 1965

Authors and Affiliations

  • M. Ferro-Luzzi
    • 1
  • R. George
    • 1
  • Y. Goldschmidt-Clermont
    • 1
  • V. P. Henri
    • 1
  • B. Jongejans
    • 1
  • D. W. G. Leith
    • 1
  • G. R. Lynch
    • 1
  • F. Muller
    • 1
  • J. -M. Perreau
    • 1
  1. 1.CERNGeneva

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