Z. D. Thomé

Inadequacy of the spectator model in deuteron break-up induced by high-energy hadrons

Abstract We discuss the experimental features of the spectator distribution in high-energy reactions on deuterons and we compare them with the quantitative and qualitative predictions of various theoretical models. We find that only a particular type of meson exchange can explain the relative channel dependence. Extending our analysis to the case of a hyperon and a nucleon in the final state, we find it more practical to look at this effect from a different point of view, namely introducing isobars in the final scattering state.

Effects of fermi motion on deuterium scattering near a resonance

SummaryIn the framework of the impulse approximation, we study the effects of Fermi motion on the evaluation of differential cross-sections for elastic scattering by deuterons. It is shown that the influence of Fermi motion may become very strong in the region of energies where a resonance occurs in the interaction of the incident particle with the individual nucleons. The calculated effects are more pronounced in the backward directions, where a factor of two may occur between the values obtained with and without account taken of the dependence of the two-particle amplitudes on the nucleon motion.RiassuntoServendosi dell’approssimazione impulsiva, si studiano gli effetti del moto di Fermi sulla valutazione della sezione d’urto differenziale per la diffusione elastica su deuteroni. Si mostra che l’influenza del moto di Fermi può divenire molto forte nella regione delle energie in cui si produce una risonanza nell’interazione fra la particella incidente e il singolo nucleone. Gli effetti calcolati sono maggiormente pronunciati nelle direzioni di rinculo, dove un fattore due può intercorrere fra i valori ottenuti tenendo conto della dipendenza delle ampiezze delle due particelle dal moto del nucleone e quelli ottenuti senza tenerne conto.РеэюмеВ рамках импульсного приближения мы исследуем влияние движения Ферми на оценку дифференциальных поперечных сечений упругого рассеяния дей-тронами. Покаэывается, что влияние движения Ферми может стать очень сильным в области знергий, где имеет место реэонанс при вэаимодействии падаюшей частицы с отдельными нуклонами. Вычисленные зффекты окаэываются более выраженными в направлении наэад, где появляется множитель два между величинами, полученными с учетом и беэ учета эависимости двухчастичных амплитуд от движения нуклона.

Scattering at low energies and the inverse problem at fixed angular momentum

Abstract We consider the inverse formalism at fixed angular momentum and examine how to associate a meaningful regular potential with a given number of scattering parameters in the effective range expansion of an S-wave phase shift. Under the assumption that there are no bound states, we expand k cotg δ ( k ) as a continued fraction in k 2 and show that the necessary condition δ (∞)− Δ (0) = 0 is sufficient in order that a given [ N / M ] Pade approximant of k cotg δ ( k ), with M ⩽ N − 1, be exactly reproducible by a regular Bargmann potential V N B ( r ). We derive explicit conditions on the coefficients of the 3 lower [ N / M ] Pade approximants (and thus on the first four scattering parameters) for the existence of unique V 1,2 B potentials which reproduce exactly such extrapolations. These potentials are found to be stable against the noise produced by experimental errors on the scattering parameters.

HIGH MOMENTUM COMPONENTS OF THE DEUTERON WAVE FUNCTION

The tail of spectator distribution for the reaction K+d −K+ π−pp is studied with the inclusion of inelastic intermediate states in the double scattering. The result seems to indicate the existence of high momentum components for the deuteron wave function.

Off-mass-shell effects in deuteron break-up by pions at low energies

SummaryThe πd → πpn differential cross-section near the 33 resonance is calculated considering the Fermi motion of the nucleons inside the deuteron and the off-mass-shell effect. The off-mass-shell extension of the π amplitude is made using a separable potential model. A comparison with experimental data is presented, with a brief discussion.RiassuntoSi calcola la sezione d’urto differenziale πd → πpn nei pressi della risonanza 33 tenendo conto del moto di Fermi dei nucleoni nel deutone e degli effetti esterni allo strato delle masse. Si determina l’estensione fuori dello strato delle masse dell’ampiezza π usando un modello a potenziali separabili. Si presenta un confronto con dati sperimentali con una breve discussione.РеэюмеВычисляется дифференциальное поперечное сечение процесса лd → лрп вблиэи 33 реэонанса, рассматривая движение Ферми нуклонов внутри дейтрона и учитывая влияние области вне массовой поверхности. Испольэуя модель раэделяемого потенциала, проводится продолжение π амплитуды на область вне массовой поверхности. Проводится сравнение с зкспериментальными данными.

On the tail of the “spectator” in k+D → ko pp

Abstract The large values of the spectator momentum distribution for large values of this variable are explained with a model based on final-state interaction of the two emerging protons. A comparison with recent experimental data is presented.

Final-state interaction effects in low-energy deuteron break-up

SummaryWe study the effects of the neutron-proton interaction as corrections to the impulse approximation calculation of differential cross-section for deuteron break-up scattering. We are mainly concerned with low-energy processes, and apply our results to pion-deuteron scattering at energies below theP33-resonance.RiassuntoSi studiano gli effetti dell’interazione neutrone-protone come correzioni al calcolo nell’approssimazione degli impulsi della sezione trasversale differenziale per lo scattering di rottura del deuterone. Si è particolarmente interessati ai processi di bassa energia, e si sono applicati i nostri risultati allo scattering pione-deuterone ad energie sotto la risonanzaP33.РеэюмеМы исследуем зффекты вэаимодействия нейтронов с протонами, как поправки к вычислению в импульсном приближении дифференциального поперечного сечения рассеяния на дейтоне, которое сопровождается расшеплением. Мы в основном рассматриваем процессы при ниэких знергиях и применяем нащи реэультаты к рассеянию пиона на дейтерии при знергиях нижеP33 реэонанса.

Relativistic correction in double scattering by deuterons

SummaryWe present a relativistic correction to the double-scattering Glauber formula arising from the relativistic correction in the definition of the centre-of-mass and relative co-ordinates. An application is made to the rho photoproduction on deuterons.RiassuntoSi presenta una correzione relativistica della formula di Glauber dello scattering doppio che deriva dalla correzione relativistica nella definizione delle coordinate del centro di massa e relative. La si applica alla fotoproduzione di ρ su deuteroni.РеэюмеМы предлагаем релятивистскую поправку к формуле двукратного рассеяния Глаубера, которая воэникает иэ релятивистской поправки в определении координат центра масс и относительных координат. Предложенный метод применяется к фоторождению р-меэона на дейтроне.