Summary
A partial-wave analysis of the low-mass (pπ+π−) system produced in K−p and π±p interactions has been performed using an isobar model formalism incorporating the assumption of the dominance of pomeron exchange. It is found that the system may be adequately described by states in the «spin-parity rule» seriesJ P = 1/2+, 3/2−, 5/2+, but the presence of waves in the series 1/2−, 3/2+, 5/2− cannot be ruled out. The dominant decay modes are Δ(1236)π and εp. The enhancement in the (pπ+π−) mass distribution at 1.5 GeV is found to be mainly 3/2− Δπ (s-wave), while the enhancement at 1.7 GeV appears to be a mixture of states decaying to both Δπ and pε. No significant phase variation is observed.
Riassunto
Si è effettuata un’analisi dell’onda parziale del sistema a massa bassa (pπ+π−) prodotto nelle interazioni K−p e π±p per mezzo di un formalismo del modello degli isobari comprendente l’ipotesi della dominanza dello scambio dei pomeroni.Si trova che il sistema può essere descritto in maniera adeguata da stati nella serie della «legge di spin-parità»J P = 1/2+, 3/2−, 5/2+, ma la presenza di onde nella serie 1/2−, 3/2+, 5/2− non può essere esclusa. I modi dominanti di decadimento sono Δ(1236)π e εp. L’aumento nella distribuzione della massa (pπ+π−) a 1.5 GeV è principalmente 3/2− Δπ (ondas), mentre l’aumento a 1.7 GeV sembra essere una miscela di stati che decadono sia a Δπ che a pε. Non si è osservata alcuna significativa variazione di fase.
Реэюме
Проводится парциальный аналиэ системы (pπ+π−) с малой массой, обраэованной в K−р и π±p вэаумодействиях, испольэуя формалиэм иэобарной модели, включаюший предположение о доминантности обмена Помероном. Обнаружено, что рассматриваемая система может быт адекватно описана с помошью состояний в последовательноьтиJ P = 1/2+, 3/2−, 5/2+, но невоэможно исключить наличие волн в последовательности 1/2−, 3/2+, 5/2−. Доминантные моды распада преставляют Δ(1236) π и εp. Пик в распределении масс (pπ+π−) при 1.5 ГзВ представляет в основном 3/2− Δπ (s-волна), тогда как пик при 1.7 ГзВ, по-видимому, представляет смесь состояний, распадаюшихся на Δπ и pε. Не наблюдается эаметного иэменения фаэы.
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Bacon, T.C., Barnham, K.W.J., Dornan, P.J. et al. Partial-wave analysis of low-mass (pπ+π−) systems produced in K−p and π±p interactions. Nuov Cim A 42, 431–444 (1977). https://doi.org/10.1007/BF02730275
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DOI: https://doi.org/10.1007/BF02730275