Summary
A liquid hydrogen bubble chamber investigation of π−p interactions has been carried out at a momentum of 2.75 GeV/c. 10645 two-prong events have been measured and the partial cross-sections are: σel=(7.2±0.1) mb, σpπ −π0=(2.8±0.1) mb, σπ −π+ n=(3.9±0.1) mb. In any state of charge, isobar production is very small. ππ mass spectra show a dominant ρ resonance centered at 750 MeV with a full width at half maximum of ⋍130 MeV (σϱ −=0.75 mb, σϱ 0=1.1 mb; forΔ 2⩽8µ2, (σϱ −/σϱ 0=1/2). There is a slight indication of the presence of the f0 (σf 0⩽0.1 mb). Usual tests of the one-pion-exchange mechanism are attempted for the ρ resonances. The ππ elastic cross-section and angular distribution are investigated as a function of the π− incident energy. Finally, the narrow peak in the (π−π+) mass spectrum in the region of 780 MeV is discussed.
Riassunto
Con la camera a bolle ad idrogeno liquido si è eseguito uno studio delle interazioni π−p ad un impulso di 2.75 GeV/c. Si sono misurati 10645 eventi a due rami e le sezioni d’urto parziali sonoσ el=(7.2±0.1) mb, σpπ−π0=(2.8±0.1) mb, σπ −π+ n=(3.9±0.1) mb. In ogni stato di carica la produzione di isobari è piccolissima. Gli spettri di massa ππ presentano una risonanza ρ predominante centrata a 750 MeV con un’ampiezza totale a metà massimo di ⋍130 MeV (σϱ=0.75 mb, σϱ 0=1.1 mb, perΔ 2⩽8µ 2, σϱ −/σϱ 0=1/2). Si ha un lieve indizio della presenza dell’f0 (σf 0≲0.1 mb). Si tentano le prove usuali del meccanismo di scambio di un pione per le risonanze ρ. Si studiano in funzione dell’energia del π− incidente le sezioni d’urto elastico ππ e le distribuzioni angolari. Infine si discute lo stretto picco nello spettro di massa (π−π+), nella regione di 780 MeV.
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Saclay-Orsay-Bari-Bologna Collaboration., Baton, J.P., Berthelot, A. et al. Single pion production in π−-p interactions at 2.75 GeV/c. Nuovo Cim 35, 713–730 (1965). https://doi.org/10.1007/BF02739336
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DOI: https://doi.org/10.1007/BF02739336