Summary
The final results of a bubble chamber experiment on double pion photoproduction in deuterium, from threshold up to 1 GeV, are reported. The total cross-sections of reactions γn→nπ−π+, γn→pπ−π0 and γp→pπ+π− are calculated, by using the spectator model. The squared-mass distributions have been fitted, and the cross-sections of reactions γn→Δ−π+, γn→Δ+π−→pπ0π− and γp→Δ++π− have been obtained. The general features of these cross-sections are consistent with a large nonresonant Δ production, accounted for in a gauge-invariant OPE model.
Riassunto
Si riportano i risultati finali di un esperimento in camera a bolle di fotoproduzione doppia di pioni su deuterio, dalla soglia fino a 1 GeV. Si sono calcolate, facendo uso del modello del nucleone spettatore, le sezioni d’urto totali delle reazioni γn→nπ−π+, γn→pπ0π− e γp→pπ+π−. Sono state aggiustate le distribuzioni di massa quadrata e sono state ottenute le sezioni d’urto delle reazioni γn→Δ−π+, γn→Δ+π−→Pπ0π− e γp→Δ++π−. Le caratteristiche generali di queste sezioni d’urto sono consistenti con un’abbondante produzione di isobaro non risonante Δ, in accordo con un modello OPE invariante per trasformazioni di « gauge ».
Реэюме
Приводятся реэультаты зксперимента на пуэырьковой камере по фоторождению двух пионов на дейтерии от порога до 1 ГзВ. Вычисляются полные поперечные сечения реакций γn→nπ−π+, γn→pπ0π− и γp→pπ+π−. Подгоняются распределения для квадратов масс. Определяются поперечные сечения реакций γn→Δ−π+, γn→Δ+π−→Pπ0π− и γp→Δ++π−. Обшие характеристики зтих поперечных сечений согласуются с интенсивным нереэонансным реждением Δ, которое общяс-няется в калибровочно инвариантной модели с однопионным обменом.
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Scuola di Perfezionamento in Fisica Teorica e Nucleare.
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Carbonara, F., Chiefari, G., Drago, E. et al. Analysis of γn→nπ+π− and γn→pπ−π0 reactions from threshold up to 1 GeV. Nuov Cim A 36, 219–234 (1976). https://doi.org/10.1007/BF02724576
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DOI: https://doi.org/10.1007/BF02724576