Energy loss and nucleon exchange in the reaction of 86Kr with 166Er

Projectile-like products from the reaction ⁸⁶Kr on ¹⁶⁶Er at 8.18 MeV/amu have been measured using a large-area position-sensitive ionization chamber. The observed element distributions for a given energy loss are found to be asymmetric. An analysis of the data in terms of the residual kinetic energy above the Coulomb barrier, however, yields symmetric and Gaussian-shaped element distributions. At large energy losses, the centroids of these Gaussian distributions exhibit a drift towards symmetric mass splits. The correlation between the variance of the element distribution σ_z² and the number of exchanged nucleons N_ex is discussed. The exchange mechanism, as described by a simple one-body dissipation model, can account for a large portion of the measured energy loss.     

Comparison of planar features of K−p interactions with e+e− annihilations and deep inelastic μp scattering

The planar features of hadronic final states in K^?p interactions at 4.5, 5.6 and 14.3 GeV c.m. energy are compared with data from e⁺e^? annihilation and deep inelastic μp scattering. A strong energy variation of the distributions (1/σ)dσ/dp_t², 〈p_t²〉_in and Σp²_{t in} is observed over this energy range. Striking agreement is found between the K^?p data at 14.3 c.m. energy and the leptonic data at similar hadronic c.m. energies. The behaviour of these distributions from K^?p data is not well described by the simple quark fragmentation model, but shows deviations similar to those attributed to hard gluon effects in leptonic interactions.     

Neutral kaon production in K+p interactions at 32 GeV/c

The production of neutral kaons in the reaction K⁺p → Kⁿ + X is studied at the incident momentum of 32 GeV/c. Inclusive cross sections and single-particle distributions are presented and compared with the data at lower energies. The total inclusive cross section amounts to 7.9 ± 0.3 mb at 32 GeV/c and is significantly higher than at lower energies due to the rapid rise of multikaon production. The fraction of Kⁿ's coming from the decay of the K¹ resonances stays roughly constant with energy between 8.2 and 32 GeV/c. In the central and beam fragmentation regions the single-particle distributions reveal no energy dependence between the 16 and 32 GeV/c data in contrast with the behaviour at lower energies, while in the proton fragmentation region the data are compatible with the trend observed at lower energies and with theoretical expectations.     

Analysis of transverse momentum and event shape invN scattering

The transverse momentum distributions of hadrons produced in neutrino-nucleon charged current interactions and their dependence onW are analysed in detail. It is found that the components of the transverse momentum in the event plane and normal to it increase withW at about the same rate throughout the availableW range. A comparison withe ⁺ e ^? data is made. Studies of the energy flow and angular distributions in the events classified as planar do not show clear evidence for high energy, wide angle gluon radiation, in contrast to the conclusion of a previous analysis of similar neutrino data.     

Neutral transverse momentum spectra in 60 and 200A·GeV16O+nucleus and proton+nucleus reactions

Transverse momentum (p _T) distributions fo inclusive photons and neutral pions at midrapidity are measured with a lead glass calorimeter in 60 and are measured with a lead glass calorimeter in 60 and 200A·Gev¹⁶O+nucleus and and proton+nucleus reactions. Inclusive photon distributions are compared for central and peripheral reactions. The degree of centrality is determined either from the charged particle multiplicity or from the remaining projectile energy in the forward direction. Deviations from a nucleus+nucleus interaction model based upon linear extrapolation from p+p reactions are observed in central¹⁶O+Au data. The variation of theaverage transverse momentum is investigated as function of centrality. The target-mass and energy dependence of π⁰ p _T distributions are presented. For¹⁶O+Au a change of slope in these distributions is observed atp _t ≈0.8 GeV/c compatible with hydrodynamic expansion models.     

Nuclide distributions for Fe-like fragments in the 136Xe + 56Fe reaction

The nuclide distributions of Fe-like reaction products from the reaction 5.9 MeV/u ¹³⁶Xe on. ⁵⁶Fe were measured as a function of total kinetic energy loss at a laboratory angle of 55°. The first and second moments of N, Z and A were obtained in addition to the correlation coefficients and the isobaric variances. We compare these results for the Fe-like fragment to those implied by previous measurements of the secondary distribution of the Xe-like fragment. We incorporate the effects of particle evaporation on both the light and heavy complementary primary distributions. There is overall qualitative agreement, but the variances are somewhat smaller than those obtained previously even after correction for particle evaporation. Evaporation calculations are also performed on the primary distributions predicted by a nucleon exchange model, and yield distributions in good agreement with the present experimental data.     

Momentum distributions of <Superscript>4</Superscript>He nuclei from the <Superscript>6</Superscript>He and <Superscript>6</Superscript>Li breakup

Experimental data on the momentum distributions of ⁴He nuclei originating from ⁶He and ⁶Li breakup on various targets are presented over a wide beam energy range. The experiment with ⁶He was performed at the DRIBs accelerator complex for radioactive beams at the Joint Institute for Nuclear Research (JINR, Dubna). The intensity of the ⁶He beam used was 5 × 10⁶ particles per second and its energy was 10 MeV per nucleon. The momentum distributions of breakup products were measured by means of the MSP-144 magnetic spectrometer. The distribution width was shown to be virtually independent of the target mass. A small value of this width, σ ～ 28 MeV/c, confirms the presence of a halo in ⁶He. The measurements performed with ⁶Li beams of energy 18 and 46 MeV per nucleon at the U-400M accelerator yielded a width value of σ ～ 50 MeV/c for the momentum distributions of ⁴He nuclei, which is intermediate between that for ⁶He and those for stable nuclei. A compilation of the widths of the momentum distributions of fragments originating from the breakup of various nuclei is presented versus the binding energy of one or two neutrons in these nuclei, the target mass and the projectile energy.     

Differential cross sections of proton compton scattering at photon laboratory energies between 700 and 1000 MeV

Differential cross sections of proton Compton scattering have been measured at the Bonn 2.5 GeV synchrotron. 78 data points are presented as angular distributions at photon lab energies of 700, 750, 800, 850, 900, and 950MeV. The c.m. scattering angle ranges from 40°–130°, corresponding to a variation of the four momentum transfer squared betweent=?0.10 tot=?0.96 GeV² at 700 and 950 MeV, respectively. Two additional differential cross sections have been measured at 1000MeV, 35.6° and 47.4°. The angular distributions show forward peaks whose extrapolations to 0° are consistent with calculated forward cross sections taken from literature. The small angle data (|t| ?0.2 GeV²) together with the calculated cross sections at 0° are also consistent with the assumption of a slope parameterB of 5 GeV^?2. For the first time a rerise of the angular distributions towards backward angles has been observed. It becomes less steep with increasing energy. The most interesting feature of the angular distributions is a sharp structure which appears betweent=?0.55 GeV² at 700MeV andt=?0.72 GeV² at 950 MeV. Such a rapid varation of the differential cross section witht has never been ovserved in elastic hadron-hadron scattering or photoproduction processes. It indicates the existence of a dynamical mechanism which could be a peculiarity of Compton scattering.     

KNπ final states in K+p interactions at 7.3 GeV/c

Data are presented on the production of the KNπ final states in K⁺p interactions at 7.3 GeV/c. The energy dependence of the KNπ final state cross sections, the effective-mass distributions, and the spectra of c.m. longitudinal momenta are given, and features of these data are compared with predictions of the generalized Veneziano (GV) model. Furthermore, we present the momentum transfer and decay angular distributions for K¹ (890), K¹ (1420) and Δ (1236) production within the KNπ final states and discuss these quasi-two-body reactions in terms of the GV model.     

(p,t) Reaction studies on some even isotopes of samarium

The (p, t) reaction on the even isotopes¹⁴⁴Sm,¹⁴⁸Sm and¹⁵⁰Sm has been investigated at an incident proton energy of 25.5 MeV. Angular distributions have been measured for transitions to the ground state and excited states up to an excitation energy of about 2.5 MeV. Especially theL=0 angular distributions are discussed.     

Neutral kaon production inK + p and π+ p interactions at 250 GeV/c

The inclusive production of neutral kaons is studied inK ⁺ p and π⁺ p interactions at 250 GeV/c. Total and semi-inclusive cross sections and average kaon multiplicities are presented and compared with the data at lower energies. The longitudinal and transverse momentum distributions and their energy dependence are analyzed. The results are interpreted in the framework of recent parton models.     

Pion-pair production on a proton by photons in the energy region of nucleon-resonance excitation

A model is proposed for describing the production of π⁺π^? pairs by real and virtual photons on protons in the energy region of nucleon-resonance excitation. The invariant-mass distributions of the π⁺π^? and π⁺ p systems at the photon point are calculated. The results are compared with available experimental data.     

The study of the (α, α′ f) reaction at 120 MeV on 232Th and 238U: (II). Fission barrier properties deduced from fission probabilities and angular distributions

The fission probabilities and angular distributions of the fission fragments for the (α, α'f) reaction on ²³²Th and ²³⁸U at a bombarding energy of 120 MeV have been measured from about 4 to 14 MeV excitation energy. Evidence for sub-barrier resonances has been found, the negativeparity ones occurring at the same excitation energy where photofission resonances have been observed. The data are analyzed with the two-humped barrier model. For ²³⁸U the data are reasonably well fitted with barriers similar to those known from the literature. For ²³²Th though, the outer barrier parameters are quite different: the height E_B = 6.6 MeV and the width (khω)_B = 1.2 MeV. Also for ²³²Th, introducing an additional mass symmetric and axially asymmetric outer barrier, as was previously found necessary for ²³⁸U, does not result in a good fit to the data at higher excitation energies.     

A study of diffusion phenomena in the rare earth region: The reaction 159Tb + 620 MeV 86Kr

Kinetic energy spectra, charge and angular distributions have been measured with ΔE-E telescopes for over twenty-five identified elements from the reaction ${}^{159}\text{Tb}\text{+ 620}\text{MeV}{}^{86}\text{Kr}$. At all angles and for all observed atomic numbers, the energy spectra indicate the presence of energetically relaxed products in the vicinity of the Coulomb barrier. Elements near the projectile also show a sizable contribution from incompletely damped events at angles close to the grazing angle. The charge distributions are peaked near the projectile Z and demonstrate a strong shape dependence on the angle of observation. The angular distributions show a weakening of the side peaking with increasing proton transfer to or from the projectile. Angular distributions and angle-integrated charge distributions have been calculated with a diffusion model which assumes the formation of a rotating intermediate complex with an l-dependent lifetime. The mass exchange between the two segments of the intermediate complex is treated as a diffusive process which is described by the master equation. Values for the diffusion constant, the overlap of the two density distributions, the mean lifetime of the intermediate complex and the spread in the average lifetime were used which semiquantitatively reproduced data from the 620 MeV ⁸⁶Kr reaction on ¹⁸¹Ta and ¹⁹⁷Au targets. Satisfactory agreement was obtained between these calculations and the data from the ¹⁵⁹Tb target. In addition, by increasing the lifetime of the complex by 30 %, the previously measured data for the ^{107, 109}Ag + 620 MeV ⁸⁶Kr reaction was semiquantitatively reproduced.     

Sequential fission angular distributions from mass-asymmetric heavy-ion reactions

The angular distributions of sequential fission fragments have been measured for the reactions of ⁴⁰Ar with ¹⁹⁷Au and ²³⁸U as a function of reaction Q-value and charge transfer. These angular, distributions are used to study the angular momentum and alignment of the deep-inelastic products which undergo fission. All of the fission fragment angular distributions are strongly focused into the plane defined by the beam and the projectile-like fragment velocity vectors. The in-plane angular distributions from reactions with uranium are isotropic for small energy losses and become anisotropic as the energy loss increases. For large negative Q-values, the in-plane anisotropy increases as the deep-inelastic products become more symmetric. The variation of the in-plane anisotropy with mass asymmetry for the two systems in this work was compared to a compilation of previous work and a consistent pattern was found. These alignment data are compared to equilibrium statistical calculations.     

Global optical model potentials for symmetrical lithium systems: 6Li+6Li, 7Li+7Li at Elab = 5–40 MeV

Angular distributions of ⁶Li+⁶Li elastic scattering were measured for E_lab = 5–40 MeV. An optical model analysis of these data together with older data of ⁷Li+⁷Li elastic scattering taken at E_lab = 8–17 MeV was performed with the aim to search for a “global” OM potential which describes elastic scattering in both LiLi systems in a broad energy range. Both surface and volume absorbing potentials can be found which fulfill this requirement if a linear energy dependence is assumed of the depths of the real as well as the imaginary potential. These depths, if fitted to individual angular distributions, are found to vary in a correlated manner with the beam energy. This is taken as indication of strong coupling between elastic, inelastic, and reaction channels. This is corroborated by the existence of resonances in reaction channels at these energies where the potential depths are most pronouncedly changing.     

The 27Al(t,p)29Al reaction at Et = 15 MeV

The ²⁷Al(t, p)²⁹Al reaction was studied at an incident energy of E_t = 15 MeV. Proton angular distributions were measured for the first 23 low-lying states. Comparisons of the data to DWBA calculations based on cluster-model and pure-configuration form factors were made which provided decompositions of the angular distributions into contributing L-values. Comparisons were also made to DWBA predictions based on microscopic amplitudes from a complete, sd-basis shell-model calculation.     

Energy straggling of Cl ions in gases

Energy-loss distributions for Cl ions in Ar-CH₄ and isobutane were measured at incident energiesE ₀=9.4, 17.1, 27.1 and 39.4 MeV up to relative energy lossesΔE/E ⁰?0.7. The full widths at half maximum are larger than predicted by the Landau-Vavilov-theory by more than a factor two. A semiempirical formula is derived which reproduces well all data measured. Reasonable agreement is obtained between this formula and other energy straggling data of heavy ions reported in the literature.     

Energy deposition and GDR emission in the reaction 209Bi(α,α′) at 240 MeV

Neutron fold distributions measured for the reaction ²⁰⁹Bi(α,α′) at 240 MeV have been analyzed with the help of Statistical Model calculations to determine the distribution of excitation energy, E_x, in the primary target fragments as a function of the projectile energy loss, EL. The reconstructed distributions in excitation energy feature a plateau which extends from the kinematical limit E_x = EL to very small excitations, indicating a variety of interactions of the beam particles with the target nucleus. The requirement of an additional coincidence with a light charged particle leads to the selection of a significant higher average excitation energy. Those results are extrapolated to explore the effects of including the excitation energy distributions in the analysis of previous GDR measurements in ²⁰⁸Pb. Corrections of the derived GDR parameters due to the partial transfer of excitation energy are suggested.