R. Mach

Elastic scattering of π±-Mesons on3He in the energy interval (68÷208) MeV

SummaryDifferent cross-section measurements of elastic scattering of π± on3He are presented. The study was done both for positive and negative pions at 98, 120, 135, 145, 156 MeV, for negative pions also at 198 and 208 MeV and for positive pions also at 68MeV. The experiment was carried out with a high-pressure helium self-shunted streamer chamber surrounded by a hodoscope of scintillation counters. The results are compared with optical-model calculations using spin-and isospin-dependent potentials. The energy dependence of the total elastic (π±,3He) scattering cross-section is discussed. Estimates of the (π3He3H) coupling constant according to the theory of Chew and Low are presented.RiassuntoSono presenti i risultati della misura della sezione d’urto differenziale di diffusione elastica (π+,3He) a 68, 98, 120, 135, 145, 156 MeV e (π−,3He) as 98, 120, 135, 145, 156, 198, 208 MeV. I dati sperimentali sono confrontati con le previsioni del modello ottico ed inoltre viene fatta una stima della costante di accoppiamento (π3He3H).РеэюмеИэмерены дифференциальные сечения упругого рассеяния пионов на ядрах3He при знергиях 68, 98, 120,135, 145, 156, 198, 208 MзB. Эксперименты вы-полнены на гелиевой стримерной камере высокого давления. Данные сопоста-вляются с расчетами по оптииеской модели. Даются оценки констаяты свяэиf2(π3He3H).

Elastic scattering of π±-mesons on4He in the energy interval (68÷208) MeV@@@Рассеяние эаряженных пионов на ядрах4He в диапаэоне знергий (68÷208) MзB

SummaryDifferential cross-section measurements of elastic scattering of π± on4He are presented. The experiment was carried out with the high-pressure helium self-shunted streamer chamber surrounded by a hodoscope of scintillation counters. Measurements were fulfilled both for positive and negative pions at 68, 98, 135, 145 and 156 MeV, for negative pions also at 120, 174 and 208 MeV. The differential and total elastic-scattering cross-sections are compared with optical-model calculations using the Kisslinger and Laplacian potentials. Some results, obtained from an energy-dependent phase shift analysis, are also presented.RiassuntoSono presentati i risultati della misura della sezione d’urto differenziale di diffusione elastica (π±,4He) a 68, 98, 135, 145, 156 MeV e (π−,4He) a 120, 174, 208 MeV. I dati sperimentali sono confrontati con le previsioni del modello ottico. È stata pure fatta un’analisi in fase dipendente dell’energia.РеэюмеПриводятся новые данные по дифференциальным сечениям упругого рассеяния эаряженных пионов на ядрах гелия-4, полученные в зкспериментах с гелиевой стримерной камерой высокого давления на синхроциклотроне ЛЯП ОИЯИ. Приводятся данные по фаэовому аналиэу, эависяшему от знергии, проводится сравнение с расчетами по оптической модели.

On the relationship between the pion and electron elastic scattering by the three-nucleon system

SummaryDifferential cross-sections ofπ-3He elastic scattering have been measured at 145, 180 and 195 MeV and compared with the optical-model predictions. In constructing the optical potential, the strong-interaction nuclear form factors are extracted from the electric and magnetic form factors, taking into account the mesonic-exchange effects in the electron-nucleus scattering. A possibility of determining the nuclear magnetic radius fromπ-3He elastic-scattering data is discussed.RiassuntoLe sezioni d’urto differenziali della diffusioneelasticaπ-3He sono state misurate a 145, 180 e 195 MeV e confrontate con le previsioni del modello ottico. Nel costruire il potenziale ottico, i fattori di forma nucleari dell’interazione forte sono stati ricavati dai fattori di forma elettrico e magnetico, tenendo conto degli effetti di scambi mesonici nella diffusione elettrone-nucleo. È discussa la possibilità di determinare il raggio magnetico nucleare dalla diffusione elasticaπ-3He.РезюмеБыли измерены дифференциальные поперечные сечения упругогоπ-3He рассеяния при энергиях 145, 180 и 195 МэВ. Проведено сравнение полученных результатов с предсказаниями оптической модели. При конструировании оптического потенциала ядерные форм-факторы сильных взаимодействий вычитаются из электрических и магнитных форм-факторов, принимая во внимание эффекты обмена мезонами в процессе электрон-ядерного рассеяния. Обсуждается возможность определения ядерного магнитного радиуса из упругогоπ-3He. рассеяния.

On applicability of the Glauber model for pion elastic scattering by helium in the δ33 resonance region

Elastic scattering of pions by3He and4He in the region of the first pion-nucleon resonance is calculated within the Glauber theory. The spin-flip and charge-exchange effects are fully taken into account. Calculated results are compared with experiment and with predictions obtained using the optical model. Some conclusions are drawn concerning the validity of approximations used in deriving the two models. The calculations make clearer some of the limitations of using the Glauber model for very low energies.

Pion-induced knock-out reactions on4He

SummaryNew experimental values of the ratio

On the energy dependence of (τ-,12C) backward-scattering cross-section

\sigma \left( {^4 He(\pi ^ + ,\pi ^ + p)^3 H} \right)/\sigma \left( {^4 He(\pi ^ + ,\pi ^ + n)^3 He} \right) + \sigma \left( {^4 He(\pi ^ + ,\pi ^0 p)^3 He} \right)

??????? ????????? p ??????? ?? ?????3He ? ????????? ??????? (68208) M?B

are given atEπlab − 110 and 160 MeV. This ratio as well as the total and differential cross-sections of pion-induced knock-out reactions on4He are discussed in terms of simple theoretical models.RiassuntoSi danno nuovi valori sperimentali del rapporto