Summary
Photoproduction of π−-mesons on deuteron has been studied in the first resonance region with an annihilation photon beam with adjustable peak energy (from 250 MeV to 400 MeV). A coincidence detection of both outgoing π−-meson and forward proton has been performed with a set of 9 multiwire proportional chambers (1700 wires) inside the gap of a spectrometer. The momentum of the second proton is computed from three-body kinematics; their distribution is found in excellent agreement with the spectator model, even at the top of the resonance. The differential cross-sections of π− have been measured from 100° to 180° (center of mass); they are in reasonable agreement with conventional multipole calculations and do not indicate an appreciable isotensor term.
Riassunto
Si studia la fotoproduzione di mesoni π− su deutoni nella regione della prima risonanza impiegando un fascio di fotoni di annichilazione di energia di picco regolabile (da 250 Me a 400 MeV). La rivelazione del mesone π− usecente e del protone emesso in avanti viene effettuata col metodo delle coincidenze facendo uso di un gruppo di 9 contatori proporzionali multifilari (1700 fili) posti nell’apertura di uno spettrometro. L’impulso del secondo protone viene calcolato partendo dalla cinematica dei problemi a tre corpi; si trova che la distribuzione di tali protoni è in eccellente accordo cn il modello dell’osservatore, anche in prossimità del picco della risonanza. Si misurano le sezioni d’urto differenziali dei π− nell’intervallo compreso tra 100° e 180° (centro di massa); esse risultano in ragionevole accordo con i convenzionali calcoli di multipolo e non indicano la presenza di un termine isotensoriale di entità apprezzabile.
Реэюме
Было исследовано фоторождение π−-меэонов на дейтерии в области первого реэонанса с испольэованием пучка аннигиляционных фотонов с регулируемым пиком знергии (от 250 МзВ до 400 МзВ). Было проведено детектирование совпадений от вылетаюшего π−-меэона и падаюшего протона с помошью системы 9 пропорцио-нальных камер (1700 проволок) внутри эаэора спектрометра. Импульс второго протона вычисляется иэ трех-частичной кинематики; их распределение находится в прекрасном согласии с моделью, даже в реэонансе. Были иэмерены дифферен-циальные поперечные сечения π− в области углов от 100° до 180° (в системе центра масс). Поперечые сечения находятся в раэумном согласии с обшепринятыми мультипольными вычислениями и не обнаруживают эаметного иэотенэорного члена.
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An erratum to this article is available at http://dx.doi.org/10.1007/BF02727460.
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Boucrot, J., Blum, D., Grossetête, B. et al. Photoproduction of π−-mesons on deuteron monochromatic photons in the first resonance region. Nuov Cim A 18, 635–653 (1973). https://doi.org/10.1007/BF02727581
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DOI: https://doi.org/10.1007/BF02727581