Reaction mechanism of <Superscript>6</Superscript>Li scattering at 600 MeV

Elastic scattering and inclusive breakup of ⁶Li particles on ¹²C, ⁵⁸Ni, ⁹⁰Zr, and ²⁰⁸Pb targets are measured at 100A MeV. The elastic scattering data are compared with single channel and Coupled Discretized Continuum Channels calculations. The coupling-effect between the elastic and the breakup channels is important even at an incident energy of 100A MeV and cannot be neglected. The inclusive breakup data are investigated for orbital dispersion effects which are found to be less significant at 100A MeV. The longitudinal momentum distributions are broader than predicted by theoretical expectations. Received: 17 December 1999 / Revised version: 9 February 2000     

Study of the Three-Nucleon Force Effects in the 2H(p, n) Breakup Reaction at 170 MeV

For the study of three nucleon force (3NF) effects in the intermediate energy region, the differential cross sections and the vector analyzing power A _y were measured for the ²H(p, n) inclusive breakup reaction at 170 MeV. The polarized proton beam of 170 MeV was injected to the deuterated polyethylene (CD₂) target and the energy of scattered neutrons were deduce by TOF method. The data was compared with the results of the Faddeev calculations with and without 3NFs. Concerning about the differential cross sections, we can see large discrepancies between the data and the calculations in the region where the energies of scattered neutrons are low, which are similar to the results of the ²H(p, p) inclusive breakup reaction at 250 MeV.     

Λ polarization in12C(π −,Λ) reactions atp π=4 GeV/c

We study theΛ formation cross sections andΛ polarizations based on the Regge pole amplitudes in theπ ^?+¹²C→Λ+X(inclusive) reactions and the exclusive kaon channel reactions atp _π =4 GeV/c. We found that the experimental data of inclusive cross sections can be reproduced qualitatively well by our calculation. As for the polarization, we have the experimental data that were reported by two different groups, although they have opposite sign and different magnitudes. Our calculated results do not agree with either set of data. We show that the sign of polarization is sensitive to the outgoingΛ kinetic energy in the inclusive reactions and to the outgoing kaon angle in the exclusive kaon channel reactions.     

Measurement of the 2H(p,n) Breakup Reaction at 170 MeV and the Three-Nucleon Force Effects

The effects of three nucleon force (3NF) have been actively studied via the nucleon–deuteron (Nd) scattering states. The differential cross sections and the vector analyzing powers A _y of the ²H(p, n) inclusive breakup reaction at 170 MeV were measured for the study of 3NF effects in the intermediate energy region. The polarized proton beam of 170 MeV was injected to the deuterated polyethylene (CD₂) target and the energy of scattered neutrons were measured by using TOF method. The data were compared with the Faddeev calculations based on modern nucleon–nucleon (NN) forces with and without the 3NF. Concerning the differential cross sections, we can see large discrepancies between the data and the calculations in the region of scattered neutron energies are low, which is similar to the results of the ²H(p, p) inclusive breakup reaction at 250 MeV.     

Interaction of 17F with a 208Pb target below the Coulomb barrier

The interaction of loosely bound (S _p = 600 keV) ¹⁷F ions with a ²⁰⁸Pb target was studied at E _lab = 86 MeV, below the Coulomb barrier, by measuring the differential cross-section for the quasi-elastic scattering and the cross-section for the exclusive breakup process ¹⁷F $ \rightarrow$ ¹⁶O + p . The small reaction and exclusive breakup cross-sections confirm the small reactivity of this system, even at low energy, and indicates that the ¹⁷F small binding energy plays a minor role in the reaction dynamics.     

Microscopic description of diffractive deuteron breakup by <Superscript>3</Superscript>He nuclei

A microscopic formalism for describing observed cross sections for deuteron breakup by threenucleon nuclei was developed on the basis of the diffraction nuclear model. A general formula that describes the amplitude for the reaction ²H(³He, ³Hep)n and which involves only one adjustable parameter was obtained by using expansions of the integrands involved in terms of a Gaussian basis. This formula was used to analyze experimental data on the exclusive cross sections for deuteron breakup by ³He nuclei at the projectile energy of 89.4MeV. The importance of employing, in calculations, a deuteron wave function that has a correct asymptotic behavior at large nucleon–nucleon distances was demonstrated.     

Proton-neutron correlation in the deuteron breakup at 56 MeV and prior-form DWBA analysis

Proton-neutron angular correlations in the ¹²C, ⁵¹V and ¹¹⁸Sn(d, pn) reactions have been measured at 56 MeV to investigate the deuteron breakup process. The elastic breakup which leaves the target nucleus in its ground state dominates the coincident spectra. The elastic breakup cross sections are estimated to be 36–48% of the inclusive breakup yields at 15° or 17.5°. In the angular correlations the protons are emitted predominantly on the side of the beam opposite to the neutrons. The experimental data have been analyzed using the prior-form DWBA. For both nuclear and Coulomb breakup, sufficient convergence of the calculations is obtained by including the pn angular momenta up to l = 2. For the nuclear breakup calculations, the l = 0 and 2 contributions dominate the cross sections. For the Coulomb breakup the l = 1 contribution is predominant. In the calculations the effect of the Coulomb breakup is seen at forward angles of the angular correlation. The DWBA calculations reproduce fairly well the coincident energy spectra and the angular correlations in the angular region where the protons are emitted on the side of the beam opposite to the neutrons. On the other hand the calculations overestimate the break-up cross sections by a factor of 2 to 10 in the angular region where the protons are emitted on the same side of the beam as the neutrons. The distributions of deuteron c.m. angular momenta that contribute to the breakup amplitude are examined to obtain information on the region of space in which the breakup reactions takes place.     

Breakup Reactions of Drip-Line Nuclei Near N = 20, 28

The one-neutron removal cross section from ²⁹Ne, ^33,35,37Mg, and ^39,41Si on a Pb target have been measured at around 240 MeV/nucleon at the RIBF (RI-Beam Factory) at RIKEN. This main goal of the experiment was to extract the inclusive Coulomb breakup cross sections in order to probe possible halo structures through their enhanced low-energy E1 strengths - so-called soft E1 excitations. The results showed significant enhancement of the one-neutron removal Coulomb breakup cross section for ³⁷Mg. This in turn provides evidence for the existence of halo structure in ³⁷Mg.     

Projectile breakup dynamics for 6Li + 59Co : Kinematical analysis of \alpha - d coincidences

A study of the kinematics of the $ \alpha$ -d coincidences in the ⁶Li + ⁵⁹Co system at a bombarding energy of E _lab = 29.6 MeV is presented. With exclusive measurements performed over different angular intervals it is possible to identify the respective contributions of the sequential and direct projectile breakup components. The angular distributions of both breakup components are fairly well described by the Continuum-Discretized Coupled-Channels framework (CDCC). Furthermore, a careful analysis of these processes using a semiclassical approach provides information on both their lifetime and their distance of occurrence with respect to the target. Breakup to the low-lying (near-threshold) continuum is delayed, and happens at large internuclear distances. This suggests that the influence of the projectile breakup on the complete fusion process can be related essentially to the direct breakup to the ⁶Li high-lying continuum spectrum.     

Contributions of exclusive pion electroproduction reactions to inclusive structure functions

The contributions of exclusive π⁺n, π⁰p, and π^?π⁺p channels to the inclusive structure function F ₂(x, Q ²) are determined from the CLAS collaboration data analysis. Reliability of the CLAS data on the inclusive structure function and single-pion electroproduction channels is verified. The total contribution of the uninvestigated π⁺π⁰n and π⁰p channels to this function and the integrated cross sections of these channels at photon virtualities Q ² = 0.4 and 0.5 GeV² are predicted.     

Cross sections for exclusive channels in\bar pp reactions at 12 GeV/c

The data obtained in an exposure of BEBC to an r.f. separated beam of antiprotons at 12 GeV/c are used to derive exclusive cross sections for reactions having one or more neutral strange particles in the final state. Particular attention is given to the estimation of the background. An upper limit of the cross section for the inclusive production of the charmed mesonD ^* is also given.     

Breakup process for 100 MeV 3He interacting with 165Ho and 166, 167Er nuclei

The projectile breakup process for 100 MeV ³He interacting with ¹⁶⁵Ho and ^{166, 167}Er nuclei was studied by measuring singles and coincidence spectra of the breakup fragments and following γ-rays. By comparing the data of the ³He-induced reaction with those of the α-induced reaction, the breakup process was found to make a large contribution to the charged-particle spectra of the ³He-induced reaction. Contributions of the elastic breakup, inelastic breakup, and breakup fusion processes were deduced individually from the particle-γ coincidence measurements.     

(e,e′K+) reaction on nuclei

We discuss the importance of the A(e, e′K⁺)_ΛA¹ reactin in nuclear physics. Cross section are given for exclusive and inclusive processes. The elementary p(e, e′K⁺)Λ, which is not well-known, is also discussed.     

Antisymmetrized Green’s function approach to (e, e′) reactions with a realistic nuclear density

A completely antisymmetrized Green’s function approach to the inclusive quasielastic (e, e′) scattering, including a realistic one-body density, is presented. The single-particle Green’s function is expanded in terms of the eigenfunctions of the non-hermitian optical potential. This allows one to treat final state interactions consistently in the inclusive and in the exclusive reactions. Nuclear correlations are included in the one-body density. Numerical results for the response functions of ¹⁶O and ⁴⁰Ca are presented and discussed.     

Compilation of coupling constants and low-energy parameters

The double-pomeron coupling strength in the dual resonance model is found in both the inclusive and exclusive regions by comparison with experiments. Double-pomeron coupling occurs in inclusive experiments in the Mueller diagram for the central plateau region. Its strength can also be bounded from its non-observation in the two-particle to four-particle exclusive experiments. The dual resonance model is used to perform the analytic continuation of a six-point amplitude between these regions. The results show that the coupling strength for two forward pomerons in the exclusive region must be less than $\text{1}\text{300}$ of that in the inclusive region. This is experimental evidence for substantial forward double-pomeron decoupling in exclusive processes.     

The breakup of 16O into He: An event-by-event study of nucleus-nucleus collisions at 75, 175 and 2000 MeV/A

We present an event-by-event study of the breakup of the ¹⁶O in ¹⁶O + emulsion nucleus interactions at 75, 175 and 2000 MeV/A. The events are categorized according to their multiplicity of projectile He nuclei. The multiplicity depends on the degree of target destruction. Although the fragmentation model describes the gross features of inclusive He spectra, an event-by-event study reveals deviations from the model. The momenta of the He nuclei, emitted from the projectile, depend on helium multiplicity and the breakup properties of the target nucleus. The probability that the ¹⁶O projectile breaks up into multiple He fragments is larger at 75 MeV/A than at 2000 MeV/A. At 75 MeV/A the mean velocity of projectile He is on the average 0.06c below the projectile velocity. This recoil velocity depends on the target nucleus destruction also for the most peripheral collisions.     

Dynamic polarization in the Coulomb breakup of loosely bound F

Angular distributions of the Coulomb breakup of radioactive ¹⁷F were measured by impinging a 10 MeV/nucleon beam on ²⁰⁸Pb and on ⁵⁸Ni to study the dynamic polarization effects. The breakup products, oxygen and a proton, were detected in coincidence. First-order perturbation theory significantly overpredicts the breakup cross section for the ²⁰⁸Pb target. Dynamical calculations with a dynamic polarization as the leading order correction were performed. The calculations reproduce the data for ¹⁷F on ⁵⁸Ni but overpredict the breakup of ¹⁷F on ²⁰⁸Pb by a factor of two at forward angles.