Rescattering mechanisms for\bar pd \to pX reactions

Inclusive proton spectra for the reactions¯pd→3πp, ¯pd→5πp, and¯p d →K¯Kmπp are calculated. In addition to nucleon exchange, the rescattering of pions and kaons, and the production and absorption of heavy mesons is evaluated. In the proton spectator momentum regime of 200 to 600 MeV/c, the role of heavy mesons is found to be negligible. The proper counting of the topological variants of pion and kaon rescattering can explain the cross sections with the exception of the¯pd→3πp channel.     

Relativistic calculation for the reactions\bar p d → 5πp and\bar p d → 3πp at rest

We present a fully relativistic calculation for ¯pd → 5πp and ¯pd → 3πp that includes angular momentum and spin dynamics. We calculate the inclusive proton distributions from two diagrams: the leading “tree” diagram, and the diagram for pion rescattering. Pion-nucleon rescattering proceeds through the Δ, in the RaritaSchwinger formalism, thus preserving the correct angular dependence. We use realistic parameterizations of the deuteron, keeping both theS andD states. The loop integrations for the rescattering amplitude and the phase space integrations have been done numerically. We find that the combined effects of a correct treatment of the rescattered pion and relativity are small in comparison with a simple non-relativistic calculation.     

Multichannel effective range approach to low energy nucleon-antinucleon interactions

MultichannelM-matrix method is applied to an N¯N-system with taking into account elasticp¯ p-scattering, charge-exchangep¯ p → n¯ n reaction andp¯ p annihilation. The isospin breaking in theM-matrix is discussed. We describe the differential and total cross-sections forp¯ p → p¯ p andp¯ p → n¯ n processes, cross-section σ_tot(p¯ p) and the real-to-imaginary ratio of the forward amplitude of elasticp¯ p scattering. The fitting leads to bound state in thep-wave near thep¯ p-threshold, which elucidates a significant role of this wave at small energies.     

Channelingeffekte bei der Lichtausbeute von Anthrazen-, Naphthalin- undp-Terphenylkristallen bei Anregung mit α-Teilchen

The scintillation light yield of anthracene atT=300 °K andT=80 °K and of naphthalene andp-terphenyl atT=80 °K was investigated for impact directions in the (a, c)-plane. The light yield was measured for welldefined integration times. The relative depth of the channeling-minimum observed for impact directions parallel to thec-axis of anthracene is found to increase with increasing integration times. For the first time channeling-minima of the light yield were observed at impact directions parallel to thec- and the [102]-axis of naphthalene and thec- and [¯102]-axis ofp-terphenyl. The [¯102]-axis ofp-terphenyl shows a more pronounced effect than thec-axis.     

Rates for the reactions\bar pp \to \pi \phi andγ φ

We study ¯pp annihilation at rest intoπφ andγφ. Rescattering by ¯K^*K+K^*¯K and ρ⁺ρ^? for ¯pp→πφ states is sizable, of order (0.90 to 2.6) × 10^?4 in the branching ratio, but smaller than experiment. For ¯pp→γφ the rescattering contributions are negligible, but theγφ channel is well explained by aρφ intermediate state combined with vector meson dominance.     

Energy levels of light antiprotonic atoms withl>0

The fine and hyperfine structure of light antiprotonic atoms in states of angular momentuml>0 is calculated. The fine (=l-dependent) structure is dominated by vacuum polarization up to a certainl-value (l=4 for¯pp), and by relativistic effects for largerl. Meson exchange is important only in the hyperfine (=spindependent) structure of theP-states. For¯pp and¯p ³He, the hadronic part of the hyperfine structure is dominated byπ ⁰-exchange.     

Many body modes of antiproton annihilation tested with antiproton production

We study the inclusive (y,¯ p) and (p,p) reactions in nuclei and check the sensitivity to the¯p annihilation mechanisms. We find that including the many body annihilation mechanisms in nuclei reduces appreciably the cross section of these reactions with respect to the evaluation considering only the one body mechanism of¯p annihilation. This shows that the¯p production reactions are more sensitive to¯p annihilation than the direct¯p annihilation reactions and makes the production experiments very useful tools to investigate the complex mechanisms of¯p annihilation in nuclei.     

Low-lying excited states of106Ag studied with the103Rh (α,nγ)106Ag and104Pd (α,pnγ)106Ag Reactions

The level scheme of¹⁰⁶Ag has been studied using the¹⁰³Rh(α,nγ)¹⁰⁶Ag and¹⁰⁴Pd(α,pnγ)¹⁰⁶Ag Reactions. The experimental information is taken fromγ-ray coincidence data using Ge(Li)-Ge(Li) and HPGe-planar Ge(Li) configurations andγ-ray angular distributions. With these measurements 126 γ rays have been assigned to¹⁰⁶Ag with 116 deexciting 78 states below 2.26 MeV in excitation. The location of the 8.4-day 6⁺ isomer is established at 89.63±0.09 keV. Many of the low-lying states are interpreted in terms of a slightly deformed rotor model.     

Thed(7Li,p)8Li cross section nearE cm=0.61 MeV

The absolute cross sectionσ of thed(⁷Li,p)⁸Li reaction near theE _cm=0.61 MeV resonance has been measured using a⁷Li ion beam and a windowless gas target system filled with D₂ gas. The proton yield of the reaction and theβ-delayedα-activity of the residual nuclides⁸Li were observed both concurrently with the elastic scattering yield, relatingσ to the Rutherford scattering cross sectionσ _R. The resulting values,σ (fromp)=143.6±8.9 mb andσ (from⁸Li)=151±20 mb, lead to a weighted mean value ofσ=153±6 mb (x ²=2.26) including all available values andσ=146±5 mb (x ²=0.05) removing some values from the data set. The consequences for the expected flux of high-energy solar neutrinos are discussed.     

Study of the excited 0+ states through conversion electron spectroscopy of neutron rich Zr and Mo fission products

A windowless Si(Li) electron detector has been used in conjunction with the gas filled fission product separator JOSEF to study totally converted transitions in Zr and Mo isotopes. The existence of twoβ-decay modes in⁹⁶Y,⁹⁸Y and¹⁰⁰Nb is confirmed. The half-lives of theβ-decaying levels feeding O ₂ ⁺ states in⁹⁶Zr and⁹⁸Zr are 6.0 ± 0.4 sec and 0.60±0.05 sec respectively. A search for other first excited O ₂ ⁺ states shows that no such states are apparent in¹⁰⁰Zr and¹⁰⁴Mo.     

Multipole mixing ratios of transitions in175Lu populated from the decay of175Hf

Electron capture decay of¹⁷⁵Hf(70 d) provides a possibility for unambiguous determination of the sign and magnitude of multipole mixing ratios for 89 keV and 114 keV transitions in¹⁷⁵Lu. This is because both gamma rays are in coincidence with the 230 keV transition which is of a pureE2 character. The results of theγ —γ directional correlation measurements, in terms ofE2/M1 mixing ratiosδ, areδ ₈₉ = 0.11±0.07 andδ ₁₁₄ = 0.465±0.005. In addition the directional correlation measurements of the 89γ- 343γ and 319γ-114γ cascades yieldδ ₃₄₃ = 0.08±0.07 andδ ₃₁₉ = ?0.152±0.015.Radioactivity ¹⁷⁵Hf from¹⁷⁴Hf(n, γ); measuredγ —γ(θ) deducedδ(E2/M1); Ge(Li) detectors.     

Evidence against a strong sub-threshold structure in the¯p p amplitude

Spectator nucleon distributions in¯pd →mπN are directly related to the antiproton-nucleon annihilation process below threshold. To demonstrate this quantitatively, we analyse the available¯pd → 3πN and¯pd → 5πN data. For these data, (and others) the shape of the annihilation spectrum in the peak region is well described by the tree diagram, and reflects mainly theS-state part of the deuteron wave function. The data are not consistent with a strong structure in the antinucleon-nucleon sub-thresh-old amplitude as reported in the dispersion analysis of¯pp while a weak structure is consistent with the existing data.     

L 2 andL 3 subshell fluorescence and Coster-Kronig yields forZ=96 from the decay of249Cf

TheL ₂ andL ₃ subshell fluorescence and Coster-Kronig yields forZ=96 have been measured by theK-L x-ray coincidence method with high resolution Si(Li) and Ge(Li) x-ray detectors. The results ν₂=0.650±0.036, ω₂=0.552±0.032, ω₃=0.515±0.034, andf ₂₃=0.188±0.019 agree fairly well with theory. New measurements of theL x-ray singles spectra of²⁴⁴Cm and²³⁸Pu with a high resolution Si(Li) detector permitted reevaluation of the values of ω₂ andf ₂₃ forZ=92 and 94 reported by Byrneet al. The revised values atZ=92 are ω₂=0.529±0.035 andf ₂₃=0.23±0.12, and atZ=94, ω₂=0.523±0.023 andf ₂₃=0.24±0.08. These revised values are in much better agreement with theory and with current experiments.     

In-beam study of174Lu isomers

Levels in¹⁷⁴Lu have been investigated using the¹⁷⁶Yb(p,3n) reaction. Prompt and delayedγ-ray spectra have been observed with a 0.56-cm³ Ge(Li) detector by a multispectrum analysis method. The half-life and decay mode of two isomeric levels, one at 240.8keV (395±15ns) and the other at 365.1keV (145±3ns) have been firmly established. Hindrance factors are discussed. New delayed transitions in¹⁷⁵Lu are also noted.     

Two meson doorway calculation forpp → Øπ including off-shell effects and the OZI rule

The leading two meson doorway contributions to the reactionpp → øπ, φπ, due to K^*K andpp intermediate states are calculated beyond unitarity approximation. The dependence of the results on the off-shell parametrization is explored and the effect of the finite width of the propagating mesons is estimated. The rates obtained from the rescattering mechanisms are in agreement with the data for ¯pp →φπ annihilation at rest. The vertices entering the calculation do not require any unexplained OZI violation, in particular no substantials? configuration in the nucleon appears to be needed.     

Electronic band structure and Li diffusion paths in (LaLi)TiO3

The electronic structure and the Li diffusion paths in the lithium doped lanthanum titanate have been studied. The band dispersion and the density of states (DOS) are calculated using the linear-muffin-tin-orbital (LMTO) method. The model structure used contains La-rich and La deficient layers, with the 2a_p × 2a_p × 2a_p unit cell and base centered C symmetry. The primitive cell contains 20 atoms represented by La₃LiTi₄O₁₂. The energy contour map, where Li ions are assumed to move within the La-deficient (002) layer, shows that the stable position of Li ions is off centers of the vacant La sites and that Li ions migrate through the bottlenecks at 2c sites surrounded by four oxygen ions.     

Black sphere model for the absorption of negative hadrons by nuclei

The slowing down of hadrons in a moderator entails an intensity loss by nuclear absorption. The loss is expected to be particularly large for negative hadrons, due to a combination of Coulomb attraction and strong local absorption. A black sphere absorption model is set up and used for numerical calculations of absorption probability per momentum loss. ForK ^? and¯p on heavy nuclei, a sharp maximum is found for kinetic energies below 0.1 MeV.     

The structure ofT=1 levels inA=14 nuclei

States in¹⁴C, populated via the¹¹B(α, p) reaction at 14 MeV bombarding energy, were investigated with the Doppler Shift Attenuation Method (DSAM). The analysis ofpγ coincidence spectra taken in a Ge(Li) detector at 0? and 120? with the particle detector near 0? with respect to the beam direction yielded the following lifetimes and lifetime limits for the states at 6.09, 6.59, 7.01 and 7.34 MeV, respectively, <20 fs, <1,200 fs, <7 fs and 160±60 fs. Shell model calculations using the MSDI and an empirical interaction fitted to nuclear states in 1p and 2s 1d shell nuclei, are shown to account very well for the experimental levels andγ-transition rates of 5 different multipolarities. The structure of the (J ^*,T)=(2⁺, 1) levels is discussed in the light of the experimentally observed T_z-dependence of the 2⁺, 1→0⁺, 1E2 matrix elements.     

Correlation between perturbation and collisional transfers in theA,B, C andb states of CO as revealed by high resolution lifetime measurements

Lifetimes and intensities of theA-X, B-A, C-A andb-a systems in CO have been measured at high spectral resolution using the High Frequency Deflection technique. Of special interest are the pressure effects observed in theA-X andb-a transitions, both as a function of the partial pressure of CO and as a function of added catalyst gas such as argon, helium and CO₂. The nature of these pressure effects are examined with the conclusion that resonance induced collision exchange takes place between theA orb states and other states that strongly perturb them. In particular, the collision exchange cross section estimated for theA state is unusually large, being the order of 10^?7 to 10^?8 cm³/s, mol. In contrast, theB andC (Rydberg) states, which are not known to be highly perturbed, showed no evidence of collision induced exchange. In addition, calculations on Franck-Condon factors and ¯r centroids have been carried out for each of the bands studied. Transition moments and oscillator strengths are also extracted from these calculations and from the new data presented in this paper, and considerable discrepancies to earlier values in the literature are found in some cases.