Yu. A. Shcherbakov

Self-shunted streamer chamber

Abstract The self-shunted streamer chambers can be used as visualizers of particle tracks and as detectors of event vertices. We discuss the operating conditions of this type of chamber in the presence of a magnetic field, and the features of the hv-pulse generator connected to the chamber. The results in the precision which can be obtained in the reconstruction of the tracks are discussed.

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.

180° Magnetic spectrometer with helium-filled streamer chamber

Abstract In this paper we describe the experimental apparatus exposed to the LNF-LEALE pion beam to measure the large-angle pion-nucleus scattering. This 180° spectrometer consists of a streamer chamber filled with helium at atmospheric pressure, placed in a magnetic field, and used for identification of scattering events. The required degree of localization and brightness of the tracks is obtained without using a Blumlein system. Finally, the momentum resolution obtainable with this spectrometer has been evaluated by a Monte-Carlo technique.

A streamer chamber filled with3He

In streamer chamber technology. For a number of experiments on pion scattering it is necessary to use a streamer chamber filled with /sup 3/He. The experimental setup used for investigation of the elastic and inelastic scattering of pions on /sup 3/He at energies of l00 to 200 MeV is described. (auth)

Inelastic reactions induced by pions on4He at 68, 120, 135, 156, 174 and 208 MeV

SummaryTotal and differential cross sections for the π+4He→π+p3H, π+4He → π+2p2n and π+4He → 3pn reactions have been measured atEπ=68, 120, 135 and 156 MeV. Total and differential cross-sections for the π−4He → π−p3H and π−4He → π−2p2n reactions have also been measured atEπ=120,135, 156, 174 and 208 MeV. The measurements have been performed using high-pressure helium-filled streamer chamber, exposed to the synchrocyclotron of the JINR of Dubna. The analysis of the (πp3H) reactions shows that the proton knock-out process is mainly a quasi-free (πp) scattering involving the Δ(1232)-resonance excitation. The same resonance also seems to be produced in the (π2p2n) reaction. The π+ absorption reaction takes place on a nucleon pair and the cross-section values turn out to be close to those of the π+d → pp reaction.RiassuntoLe sezioni d’urto totali e differenziali delle reazioni π+4He → π+p3H, π+4He → π+2p2n e π+4He → 3pn sono state misurate aEπ=68, 120, 135 e 156 MeV. Anche le sezioni d’urto totali e differenziali delle reazioni π−4He → π−p3He e π−4He → π−2p2n sono state misurate aEπ=120, 135, 156, 174 e 208 MeV. L’esperimento è stato eseguito al fascio di pioni del sincrociclotrone del JINR di Dubna, usando una camera a streamer ad alta pressione riempita con elio. L’analisi delle reazioni (πp3H) ha mostrato che il processo di knock-out del protone è prevalentemente uno scattering su protone quasi libero con eccitazione della risonanza Δ(1232). La stessa risonanza sembra essere prodotta anche nelle reazioni (π2p2n). La reazione di assorbimento di π+ avviene prevalentemente su coppie di nucleoni ed i valori della sezione d’urto sono prossimi a quelli della reazione π+d → pp.

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.

4He(π±, π±p)3H and4He(π±, π±2p2n) reactions induced by pions of 120, 135 and 156 MeV

SummaryWe measured4He(π±, π±p)3H and4He(π±π{±}2p2n) reactions at 120, 135 and 156 MeV. We found that the π+π- ratio is less than for free (π+p)/(π-p) elastic scattering.

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.

Elastic scattering of π+ and π− mesons on3He at 154 MeV

SummaryThe differential cross-sections for the elastic scattering of π+ and π− mesons on3He have been measured at 154 MeV with a high-pressure streamer chamber for angles between 30° and 160° (c.m.s.). The total elastic cross-sections are also presented.RiassuntoSi sono misurate le sezioni d’urto differenziali per lo scattering elastico di mesoni π+ e π− nell’3He a 154 MeV con una camera a scintille ad alta pressione per angoli compresi fra 30° e 60° (c.m.s.). Si danno anche le sezioni d’urto elastiche totali.