Folding model analysis of pion elastic and inelastic scattering from 6Li and 12C

π ^±-Nucleus scattering cross sections are calculated applying the Watanabe superposition model with a phenomenological Woods-Saxon potential. The phenomenological potential parameters are searched for π ^± scattering from ⁶Li and ¹²C to reproduce not only differential elastic cross sections but also inelastic and total and reaction cross sections at pion kinetic energies from 50 to 672 MeV. The optical potentials of ⁶Li and ¹²C are calculated in terms of the alpha particle and deuteron optical potentials. Inelastic scattering has been analyzed using the distorted waves from elastic-scattering data. The values of deformation lengths thus obtained compare very well with the ones reported earlier.     

Differential cross section for elastic π± helium isotopes scattering from 25 to 65 MeV

Measurements of absolute elastic-scattering differential cross sections for π^±He at T^lab_π = 30.2 MeV, 45.1 MeV and 65.0 MeV and for π^±-⁴?⁴He at T^lab_π = 25.1 MeV and 51.1 MeV have been made in the angular range 40° to 145°. An overall accuracy of about ±5% was achieved. The results are compared with available theoretical calculations.     

Untersuchung der Kernphotoreaktionen12C(γ,n),12C(γ, 2n),39K(γ,n) und40Ca(γ,np) bis zur Mesonenschwelle

In order to obtain data on the photon absorption process between the giant resonance and the meson threshold the cross sections of the reactions¹²C(γ,n)¹¹C,¹²C(γ, 2n)¹⁰C,³⁹K(γ,n)³⁸K^g, and⁴⁰Ca(γ,np)³⁸K^g have been determined by the analysis of yield curves at the 140 MeV electron synchrotron of the PTB. Though the (γ,n) cross sections grow small with increasing photon energy they are different from zero up to energies of 60 MeV and above. The cross section of the reaction¹²C(γ, 2n) is extremely small; its highest value amounts to 0.15% of the highest value of the¹²C(γ,n) reaction. The measured⁴⁰Ca(γ,np) cross section is of the order predicted by the naive quasi-deuteron model. The integrated cross sections of the above reactions up to 140MeV are 85±7,0.90±0.10, 139±16, and 76±7MeVmb respectively.     

Phenomenological local potential analysis of π+ scattering

π⁺-nucleus scattering cross section are calculated by solving a Schrödinger equation reduced from the Klein-Gordon equation. Local potentials are assumed, and phenomenological potential parameters are searched energy dependently for π⁺ scattering from ¹²C, ⁴⁰Ca, and ²⁰⁸Pb to reproduce not only differential elastic cross sections but also inelastic and total and reaction cross sections at 800 MeV/c pion laboratory momentum. The collective model is used to calculate the angular distributions of differential inelastic cross sections for pions leading to the lowest 2⁺ and 3^? states of ¹²C. The deformation parameters and lengths are extracted and compared to the corresponding ones from other works. Local potentials well describe the scattering of pions from nuclei.     

Measurement of positive pion production from 14N at low momentum transfer

Double differential cross sections of the reaction ¹⁴N(e, π⁺) have been measured at E₀ = 173.5 MeV for pion production angles of Θ_π = 25° and 100° which correspond to momentum transfer values of q² = 0.22 and 1.14 fm². Using the virtual photon theory single differential cross sections of the reaction ¹⁴n(γ, π⁺)¹⁴C_g.s. are extracted from the measured data. The data are compared with recent DWIA calculations and indicate a larger nuclear spin-flip transition matrix element between ¹⁴N and ¹⁴C than that obtained from β-decay. Mixing parameters for shell model wave functions of ¹⁴N and ¹⁴C ground states are derived from the data.     

A search for πNN bound systems

The d(π⁺, π⁻)T⁺⁺⁺ and the d(π⁻, π⁺) T⁻ reactions were studied at an incident pion energy of 260 MeV. Outgoing negative pions were detected at 35° and 55° in the first reaction, and the positive pions at 45° in the second. Indications for structures corresponding to a (π⁺pp) system with a mass of 2003.0±1.0 MeV and a (π⁻nn) system with a mass of 200.1±1.5 MeV were observed with marginal statistical significance. Upper limits for the cross sections are obtained.     

Backward πd scattering between 140 and 260 MeV

Differential cross sections for elastic scattering of pions by deuterons have been measured for centre-of-mass angles between 130° and 175°, and at laboratory energies 141, 177, and 260 MeV for π⁺, and at 151, 185, and 189 MeV for π^?. At 177 and 260 MeV the cross sections are a factor of 2 lower than the predictions of three-body theories.     

T = 1 excitation mechanism in pion induced reactions on 12C

The cross sections for the reactions π^± → π^±, π⁰ on ¹²C with excitation of the T = 1 states are calculated for the N₃₃¹ energy region. The Chew-Low amplitude for pion-nucleon scattering is used in the framework of impulse approximation which has been supported by recent calculation of pion scattering with excitation of definite nuclear states.     

Radiative width for the 10.35−6.92 MeV transition in 16O

From a measurement of the cross section for ¹²C(α, γ)¹⁶O at the E_α = 4.253±0.014 MeV(E = 10.352±0.011 MeV) resonance, the radiative width for the 10.35 MeV (J^π = 4⁺) to 6.92 MeV (J^π = 2⁺) transition was determined to be Γ_γ = 58±7 meV. This is somewhat higher than the value predicted by large j-j shell-model calculations, but agrees well with predictions based on the rotational and the SU(3) models for a 4p-4h band, and the deformed- basis calculation of Green and Brown.     

The (p, π±) reactions on 12,13C at 200 MeV

Angular distributions from the (p, π^±) reactions have been measured at 200 MeV on ¹²C and ¹³C leading to discrete final states in the residual nuclei. A comparison of the cross sections is made between transitions to isobaric analog and non analog final states. Differences between the (p, π⁺) and (p, π^?) reactions are found in the shape and magnitude of the differential cross section as well as in the energy variation.     

On the pion-nucleus dynamics at low energies

Low-energy pion scattering (up to 50 MeV) on ¹²C and ¹⁶O is described quantitatively in the framework of the UST approach. It is shown that at T_π ∼ 50 MeV the differential cross sections arise as a result of a strong interference between the pure potential and absorption channels. The importance of nuclear structure effects in the pion-nucleus dynamics at low energies is discussed.     

Measurements of the (γ, n0) reaction on 12C and 16O and the investigation of the reaction mechanism

Differential (γ, n₀) cross sections on ¹²C and ¹⁶O have been measured for photon energies 60 MeV ? E_γ ? 160 MeV. These results combined with the corresponding (γ, p₀) cross sections support an absorption mechanism of the photon by neutron-proton pairs.     

Lifetime of the second excited state of K

Energy distributions of neutrons from the (d, n) reactions on ^12–14C leading to unbound states of ^13–15N have been measured at 6.3 or 6.5 MeV deuteron energy. Angular distributions have been extracted for ^{13, 14}C(d, n) transitions and analysed with DWBA using the extra-polation technique to give l-values and transition strengths for ten unbound states in ¹⁴N and six in ¹⁵N. For the ¹⁵N level at 10.541 MeV it is concluded that J^π is $\text{3}\text{2}$^?. A new ¹⁵N level is observed at 11.44 MeV. The 0° (d, n) cross sections have been set in proportion to (p, p₀) resonance cross sections, and a pronounced l-dependence of the ratio is obtained.     

Measurements of 12C(π+, πN)11C and 19F(π+, πN)18F cross sections near the 32, 32 resonance

Reaction cross sections for ¹²C(π⁺, πN)¹¹C at 134, 161, 177, and 200 MeV and for ¹⁹F(π⁺,πN) at 161, 177, and 200 MeV were measured by activation methods.     

Direct Measurement of 12C+4He Fusion Cross Section at E cm = 1.5 MeV at KUTL

¹²C+⁴He fusion reaction at E _cm  = 0.3 MeV is one of the main reaction in ⁴He-burning in stars, and is very important in nuclear synthesis. However the fusion cross section has not been determined yet in spite of 40 years efforts in the world. Recently we succeeded in the measurement at 1.5 MeV. We have a plan to make direct measurement of the total fusion cross section down to 0.7 MeV at Kyushu University Tandem accelerator Laboratory (KUTL), and to determine the cross section at 0.3 MeV by extrapolation.     

The 24Mg(α, α')24Mg reaction; statistical analysis

The ²⁴Mg(α, α')²⁴Mg reaction to the 1.37 MeV state has been studied over an α-energy range of 9.625–13.825 MeV, in ≈40 keV steps, and over a 25°–160° angular interval. These cross sections have been analysed in terms of statistical theory and a number of deviations from its predictions are found. These deviations point to the importance of non-statistical processes, such as intermediate structure, to the α-scattering. The average compound nuclear width o₁ 62±7 keV is found for ²⁸Si over the 18–22 MeV excitation.     

Pion-nuclear total cross sections near the 32, sol32 resonance

The π⁺ total nuclear cross sections for ⁹Be, ¹²C, ¹⁶O, and ²⁷Al have been measured in the energy range 114 to 210 MeV, while π^? data have been taken at 153 MeV. In the center-of-mass coordinate system the π-nucleus total cross sections reach their maximum value near the π-nucleon $\text{(}\text{3}\text{2}\text{,}\text{3}\text{2}\text{)}$ resonance (T_π^C.M.= 1.52 MeV) where they scale as $\text{A}{}^{\mathrm{<mtext>2</mtext><mtext>3</mtext>}}$. The measured total cross sections exhibit considerable broadening with respect to the π-nucleon resonance.     

Electromagnetic corrections to the s-wave scattering lengths in pionic hydrogen

Motivated by the recently performed X-ray precision experiments on pionic hydrogen (preceding paper), we reconsider the problem of electromagnetic corrections to the π - N scattering lengths. Based on a relativistic two-channel approach, we find corrections to the π⁻p elastic and single-charge-exchange (SCE) scatering lengths due to the point-Coulomb interaction, the finite-size Coulomb interaction (including the pion size), the first-order vacuum polarization (Uehling potential) and the (π⁻p) - (π⁰n) mass difference (mass difference effect). We also estimate the contribution due to the (γ,n) decay channel. The total corrections to the elastic and the SCE scattering lengths are found to be δ_ε = −(2.1 ± 0.5) × 10⁻² and δ_Γ = −(1.3 ± 0.5) × 10⁻². Previously published values for the corrections are critically compared with our results.     

Scattering of <Emphasis Type="Italic">π</Emphasis><Superscript>±</Superscript> mesons on a <Superscript>9</Superscript>Be nucleus in the Δ<Subscript>33</Subscript>-resonance region

Within the Glauber diffraction theory of multiple scattering, the differential cross sections for the elastic and inelastic scattering of π^± mesons are calculated for energies in the range between 130 and 260 MeV. This is the region where the broad Δ₃₃ resonance in the π^±N system occurs, the maximum corresponding to this resonance being at approximately 165 MeV. The wave function for the ⁹Be nucleus was chosen on the basis of the 2αN multicluster model. The sensitivity of the resulting differential cross sections to the target-nucleus wave functions computed with various intercluster-interaction potentials, to the contributions of wave-function components, and to various scattering multiplicities in the Glauber operator Ω is analyzed. A comparison with experimental data and with the results of other calculations is performed, and conclusions concerning the quality of the wave functions used and advantages of the present approach are drawn.