Pion production by protons on nuclei near the threshold

We propose including in the calculation of the cross section of the process p + N → N + N + π the process of pion production and absorption that proceeds through creation of a Δ-resonance. By taking into account the energy dependence of Δ-resonance width, the contribution of deuteron channel is included in the cross section of π⁰-, π⁺-meson production.     

Elastic pion-deuteron scattering near the 3-3 resonance

The elastic scattering of positive pions by deuterium has been studied at seven energies between 82 MeV and 292 MeV laboratory kinetic energy in the angular range between 30° and 130° (lab). The results are compared to recent relativistic three-body calculations.     

The charge exchange reaction dp → (pp)n

The ratio of the differential cross section of the charge exchange reaction of the deuteron to that of the nucleon, at small transferred momenta, has been discussed in order to estimate the spin-dependent part of the np → pn charge exchange amplitude.      

Large angle pion-carbon scattering near the πN(3, 3) resonance

Pion-carbon 12 elastic and inelastic scattering was measured for both π⁺ and π^? at 162 MeV between 135° and 180°. For this purpose, the angular range of the SIN pion spectrometer was increased to 180° by placing a magnet at the target position. In addition, an amplitude analysis taking Coulomb effects into account was performed.     

Pion absorption effects in the reaction 3H(π+, π0)3He

We show that in Glauger theory the angle integrated cross section for ${}^3\text{H}\text{(π}{}^{\mathrm{+}}\text{, π}{}^0\text{)}{}^3\text{He}$ has no peak as a function of energy through the 3,3 resonance region, thus suggesting a direct measurement to elucidate the nature of (π⁺, π⁰) reactions.     

2H( 3He, t)2p reaction at 2 GeV

The exclusive ²H( ³He, t)2p reaction has been studied at 2 GeV for energy transfers up to 500 MeV and triton angles up to 3.4^°. The protons were measured in the large acceptance magnetic detector DIOGENE, in coincidence with the forward tritons detected in a dedicated magnetic arm. The energy transfer spectra extend well above the pion threshold. However, in the region of Δ excitation, the yield is less than 10% of the inclusive ²H( ³He, t) cross-section, which indicates the small contribution of the ΔN ↦ NN process. The angular distributions of the two protons in their center of mass have been analysed as a function of energy transfer and triton angle and a Legendre polynomial decomposition has been achieved. These data have been compared to a model based on a coupled-channel approach for describing the NN and NΔ systems. Received: 21 October 2002 / Accepted: 15 November 2002 / Published online: 11 March 2003 RID="a" ID="a"e-mail: ramstein@ipno.in2p3.fr RID="†" ID="†"Deceased. RID="†" ID="†"Deceased. RID="d" ID="d"Present adress: School of Engineering, J?nk?ping University, P.O. Box 1026, S-551 11 J?nk?ping, Sweden. Communicated by M. Gar?on     

The (γ, n) reaction on 16O between giant resonance and pion threshold

A new TOF facility has been built for measurements of differential (γ, n) cross sections to discrete final states of light nuclei in the photon energy range between giant resonance and pion threshold. The observed neutron angle θ_n can continuously be varied between 0° and 150°, and additionally measurements at 175° and 180° are possible. Differential cross sections for the reaction ¹⁶O(γ, n₀)¹⁵O are presented for E_γ = 60 MeV (40° ? θ_n ? 149°) and for θ_n = 90° (60 MeV ? E_γ ? 160 MeV). The results, combined with the corresponding (γ, p₀) cross sections, indicate an absorption mechanism of high energy photons by neutron-proton pairs.     

Excited states of 188Ir populated by the (α, 3n) reaction

The deexcitation of states in ¹⁸⁸Ir, formed through the ¹⁸⁷Re(α, 3n)¹⁸⁸Ir reaction, was studied using in-beam and off-beam gamma and electron spectroscopy techniques. A new level scheme, exhibiting a rather high level density, is presented. An interpretation of the structure of these states is attempted using information on one-quasiparticle intrinsic states from neighboring oddproton and odd-neutron nuclei.     

Level structure of V from the Ti(p, nγ)V reaction

Measurements of level positions and decay modes in ⁴⁷V were carried out using the ⁴⁷Ti(p, nγ)⁴⁷V reaction. Spin and mixing ratio assignments are made for levels below 1.8 MeV excitation using a statistical compound nuclear calculation. The level structure of ⁴⁷V is compared with recent theoretical predictions.     

Pion small-angle multiple scattering at energies spanning the (3,3) resonance

The small-angle multiple scattering of positive and negative pions has been measured for C, Al, Cu and Pb targets throughout an energy range spanning the (3, 3) resonance. The measurements were made using two-dimensional multiwire proportional counters placed in the pion beam. All previous multiple scattering data for electrons and protons as well as these new data for pions are used to recalculate the empirical terms in the Moliere theory of multiple scattering. A second-order Born approximation multiple scattering theory has been devised for spin zero particles. Modified Moliere theory gives a better fit to the experimental data than the second-order Born calculation. Because the updated Moliere theory contains much simpler equations and gives closer agreement with experiment, it is recommended in place of the more sophisticated theory for the interpretation of new experimental data.     

Investigation of 16O excited states via the 14N(3He,p) reaction

The reaction ¹⁴N(³He, p)¹⁶O has been investigated at a bombarding energy of 15.0 MeV, using a differentially pumped gas target. Angular distributions were measured for 30 levels below 16.5 MeV in excitation. Data were compared with shell-model calculations of Zuker, Buck and McGrory for states whose correspondence with theory is established. Many states are found to possess a large compound-nucleus reaction component. Several previously unreported levels are observed at high excitation. Angular distributions for all except the weakest levels have been compared with DWBA calculations.     

Low-lying states of 6He studied via the 6Li(t,3He)6He reaction

We present the recent experimental results on the ⁶He structure studied by the ⁶Li(t, ³He)⁶He reaction at 336 MeV. Above the conspicuous peaks for ground and first excited states for ⁶He, we have observed a broad structures at E _x∼ 5 MeV, and E _x∼ 15 MeV. The angular distribution of this structure exhibits the dominance of a ΔL = 1 transition, indicating the existence of intruder dipole states at low excitation energies in ⁶He. A slight admixture of positive-parity states in this structure has been indicated as well. Received: 1 May 2001 / Accepted: 4 December 2001     

Pion photoproduction on 3He at and above the 3-3 resonance

The differential cross section for the ${}^3\text{He}\text{(γ, π}{}^{\mathrm{+}}\text{)}{}^3\text{H}$ reaction has been measured at fixed values of q² in the region of the first resonance, and at fixed θ_π versus q² up to 13 fm^?2. The observed shift of the resonance towards lower energies, and the absence of a minimum near 11.6 fm^?2 might be explained by recent theoretical calculations.     

Study of the structure of unstable nuclei through the reaction experiments

Along with the development of the radioactive nuclear beam facility, the study of the structure of unstable nuclei has progressed rapidly over the last few decades. Due to the weakly binding property, the structure information of the unstable nuclei comes primarily from the scattering or reaction experiments. Therefore it would be very important to understand clearly the reaction mechanism involved in the experiment. We outlined here the major reaction mechanisms which are adequate to the study of unstable ...     

D+CD4→CD3+D2反应的四维量子散射计算

运用约化维数量子动力学理论 ,利用含时波包法 ,对反应D +CD4 →CD3+D2 进行了四维量子散射计算 .将反应多原子CD4 看作双原子D—CD3,反应D +CD4 →CD3+D2 看作单原子 双原子反应 ,把体系的反应简化为四维散射问题 .波函数的传播采用分裂算符法 ,为避免格点边界处含时波函数的边界反射 ,采用了光学吸收势法 ,在格点边界处引入光学势 ,消除边界反射 .根据CD4 分子的C3v对称性 ,选取了Jordan和Gilbert提出的半经验势能面 .计算结果表明 ,反应概率随平动能的变化图像 ,呈现出显著的量子共振特性 ,这是很多提取反应的共同特征 .而不同振动态下的反应概率随平动能的变化表明 ,随振动量子数的增大 ,反应概率有明显提高 ,且反应阈能明显降低 ,这说明反应分子的振动能对分子的碰撞反应有重要贡献 .而对基态和第一振动激发态时散射截面的计算 ,也证明了这一结论 .同时 ,还分别通过计算量子数j,k ,m对反应概率的影响 ,对该反应的空间取向效应进行了研究 ,并与H +CH4→CH3+H2 反应进行了比较 .     

Selectivity of the 16O(7Li, α) reaction and states with (sd)3 and (sd)2(fp)1 configurations in 19F

The ¹⁶O(⁷Li, α)¹⁹F reaction has been studied at 35 MeV up to 11 MeV excitation energy. Comparison with the ¹⁶O(⁶Li, ³He)¹⁹F and ¹⁶O(⁶Li, t)¹⁹Ne reactions shows very good agreement up to 5.5 MeV excitation energy and large differences at higher excitation energies which can be explained by different angular momentum matching conditions in the different reactions. The identification of mirror states in A = 19 and of states with (sd)³ and (sd)² (fp)¹ configurations in ¹⁹F are discussed.     

Study of the (p,pn) reaction in light nuclei

The (p, pn) reaction on ²H, ⁶Li, ⁷Li, ⁹Be has been studied at 47 MeV bombarding energy. Excitation energy spectra and energy sharing spectra are presented. Fragmentary information on ¹⁰B, ¹¹B and ¹²C was also obtained. Sequential decay contributions to the ⁶Li(p, pn)⁵Li¹ reaction suggest an admixture of parentage $\text{(α)π(}\text{p}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{)π(}\text{d}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}\text{)}$ for the (3^?), 23 MeV excited state of ⁶Be. A possible 15.5 MeV excited state in ⁶Be is reported. An extensive study of the ⁹Be (p, pn)⁸Be reaction for 45 MeV protons was made. Results for θ_p = θ_n = 25°, 30°, 35°, 40°, 45°, 55°, 65°; θ_n = 40°, θ_p = 25°, 30°, 35°, 40°, 45°, 55°, 65°; θ_p/θ_n = 40°/45°, 38.5° are reported and compared to DWIA calculations. Agreement is good when the lower momentum components of the wave function are sampled, and deteriorates as higher momenta are required. Results are in agreement with the Cohen and Kurath spectroscopic factors for ⁹Be.