Summary
Measurements of the energy spectra and the excitation yields of π− and π+, from the reactions γ+p → π−+π++p and γ+p → → π++π0+n together, were done at a laboratory angle 58.2° with bremstrahlung maximum energies up to around 1 GeV, using the 1.3 GeV electron synchrotron. The differential cross-sections were derived and compared with a simple isobar model. The results show that, while the energy spectra and the excitation yields ofπ − agree with the model of theT=1/2 isobar excitation decaying into Δ+π as well as with the existing data, those of π+ show some discrepancy with the same model. Discussions are given to explain the particular feature of π+ distributions observed in the present experiment.
Riassunto
Per mezzo dell’elettrosincrotrone di 1.3 GeV si sono eseguite misure degli spettri di energia e delle rese di eccitazione di π− e π+ dalle reazioni combinate γ+p → → π−+π++p e γ+p → π++π0+n, ad un angolo di 58.2° nel sistema del laboratorio con energie di bremsstrahlung massime sino a circa 1 GeV. Si sono dedotte le sezioni d’urto e le si è confrontate con un semplice modello isobarico. I risultati mostrano che, mentre gli spettri di energia e le rese di eccitazione del π− concordano col modello della eccitazione dell’isobaroT=1/2 che decade in Δ+π e con i dati esistenti, quelli del π+ presentano qualche discordanza con il suddetto modello. Si discute il modo di spiegare il particolare comportamento delle distribuzioni dei π+ osservate in questo esperimento.
Реэюме
Испольэуя злектронный синхротрон 1.3 ГзВ, были проведены иэмерения знергетических спектров и выходных воэбуждений π− и π+ иэ реакций ρ+p → → π−+π++p и ρ+p → π++πo+n при лабораторном угле 58.2°, с максимальными знергиями тормоэного иэлучения вплоть до 1 ГзВ. Выводятся дифференциальные поперечные сечения, которые сравниваются с простой иэобарной моделью. Полученные реэультаты покаэывают, что хотя знергетические спектры и выходные воэбуждения для π− согласуются с моделью иэобарного воэбужденияT=1/2, которое распадается на Δ+π, а так же с сушествуюшими данными, то знергетические спектры и выходные воэбуждения для π+ обнаруживают некоторое расхождение с той же моделью. Проводятся обсуждения, чтобы общяснить особенность π+ распределений, наблюденных в настояшем зксперименте.
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Kusumegi, A., Mishina, M., Murata, Y. et al. Double-pion photoproduction off protons below 1 GeV. Nuov Cim A 7, 727–752 (1972). https://doi.org/10.1007/BF02728807
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DOI: https://doi.org/10.1007/BF02728807