THE π-NUCLEUS INELASTIC SCATTERING AND THE NUCLEAR CORE EXCITATION FOR 13C

Using the DWIA with eikondl distorted waves and by considering nuclear core excitation, we we calculate the differential cross section of the inelastic scattering for the excitation of the 3/2^- (3.68 Mev) and the 5/2^- (7.55 Mev) states in ¹³C at T_π =180 Mev. Our results agree well with the expetiments data.     

Giant magnetic dipole analog excitations by the allowed muon capture in 1p-shell nuclei

The distributions of the allowed muon capture strengths in 1p-shell nuclei are shown to exhibit a tendency to concentrate in a few low-lying daughter states. These strong excitations are analogs of the giant magnetic dipole transitions, predicted by Kurath, and observed in inelastic electron scattering. Similar excitations are expected in 1S radiative pion capture and low-energy charged pion photoproduction processes.     

Inelastic Pion Scattering from 12C at 800 MeV/c

The differential cross section of the inelastic scattering of pion at 800 MeV/c fir the 3^- excited states of ¹²C is calculated by making use of eikonal approximation and the collective coordinate. The calculation indicates that the 3_- state of ¹²C is octupole vibrational state.The results are in agreement with experimental data.     

ON THE REACTION MECHANISM AND THE SELECTION RULE IN THE DOUBLE CHARGE EXCHANGE REACTION OF PIONS ON NUCLEI (DCX)-A STUDY OF THE CONNECTION BETWEEN THE 2β-DECAY AND DCX ON jP=O+ NUCLEI

It is shown that in the pion induced double charge exchange reaction on J^p=O⁺→O⁺ nuclei,there exists a possible new reaction mechanism π⁺(Δ⁰,Δ⁺⁺)π^- or π⁺(Δ^-,Δ⁺)π^- in so-called single step process,while that old speculative mechanism π⁺(N,Δ)π^- or π⁺(N,Δ)π^- is firbidden by a well-known selection rule which has been indicated in the theory of the nuclear 2β-decay.     

π Meson interaction on He at 120, 145 and 165 MeV

The total cross sections and the differential cross sections of π⁺-⁴He elastic and inelastic reactions at E_π=120, 145 and 165 MeV have been measured using a 38 cm diffusion cloud chamber in a magnetic field exposed to the Frascati Laboratories' pion beam. Total π⁺ track lengths of (2141 ± 10) × 10³ cm, (3435 ± 10) × 10³ cm and (2413 ± 10) × 10³ cm were measured at the three considered energies, respectively. The elastic cross-section data are in good agreement with the results of the Dubna-Torino collaboration. The total inelastic cross sections have been obtained taking into account the contributions from all the inelastic channels. The analysis of the various inelastic processes has allowed us to distinguish five main reaction mechanisms, which compare reasonably with the existing data and with the models for pion-light-nuclei interactions.     

Skyrme型N∧相互作用下超越平均场模型的∧超核研究

使用超越平均场Skyrme-Hartree-Fock（SHF）模型对_∧9Be,_∧∧10Be,_∧13C和_∧21Ne进行计算,采用SLy4参数组的Skyrme力作为NN相互作用力,采用最近提出的SLL4参数组的Skyrme力作为N∧相互作用。计算中包含了超子的自旋-轨道力以再现单粒子态的自旋-轨道能级分裂和不交叉效应,并采用BCS方法处理对力。讨论了不同组态超核的相关性质,包含12C⊗∧[000]1/2+,12C⊗∧[110]1/2-,12C⊗∧[101]3/2-和12C⊗∧[101]1/2-及8Be⊗∧[000]1/2+,8Be⊗∧[110]1/2-,8Be⊗∧[101]3/2-和8Be⊗∧[101]1/2-。计算了_∧9Be,_∧13C的低激发能谱并与实验值进行了比较。结果表明,采用的超越平均场SHF模型能很好地再现∧超子占据s_∧轨道的正宇称能级。对8Be的计算结果表明该模型可以很好地再现8Be的集团结构,可以得出_∧9Be的真实超核态能级和9Be类似态。对_∧9Be及_∧13C的计算均再现了自旋双重态（3/2+,5/2+）,但是得到的双重态能级差依然与实验值有出入。此外,对于上述超核体系均在∧超子占据∧[000]1/2+轨道时产生了收缩效应。还对_∧21Ne进行了计算并和超越平均场RMF模型计算结果进行比较,发现两者计算结果虽有细节上的出入,但是结果基本一致。The beyond-mean-field Skyrme-Hartree-Fock approach is adopted to investigate the properties of _∧9Be, _∧∧10Be, _∧13C and _∧21Ne. The nucleon-nucleon (NN) interaction SLy4 and the nucleon-hyperon(N∧) interaction Skyrme-type SLL4 are used. The spin-orbit force of hyperon is included to show the spin-orbit splitting and non-crossing effect with BCS method to deal with pairing force. Energies of different configurations, such as 12C⊗∧[000]1/2+, 12C⊗∧[110]1/2-, 12C⊗∧[101]3/2-, 12C⊗∧[101]1/2-, 8Be⊗∧[000]1/2+, 8Be⊗∧[110]1/2-, 8 Be⊗∧[101]3/2- and 8Be⊗∧[101]1/2- are given and used to study the effects of ∧ occupying different orbitals. The calculated energy spectra, including both positive-and negative-parity levels, are given and compared to the experimental data. The observed positive-parity spin-doublet (3/2+,5/2+) are successfully reproduced, but the energy difference needs further investigation. The two well known band structures corresponding to the genuine hypernuclear states and the 9Be-analog states are also obtained and compared with the observed ones. The shrinkage effect of ∧ occupying ∧[000]1/2+ is investigated through the density distributions of nuclear core. And finally the calculation results of _∧21Ne are given and compared with the results of RMF method, which are nearly the same but with differences in some details.     

K+ Inelastic Scattering From 2+, 3- State of 12C at 800 MeV/c

The differential cross sections of the inelastic scattering 6f K⁺ at 800 MeV/c on 2⁺, 3^- excited states of ¹²C are calculated by means of the eikonal approximation and the collective coordinate. It seems that the 2⁺ state of ¹²C is quadrupole rotational state, the 3^- state of ¹²C is octupole vibrational state. The results are in agreement with experimental data.     

Continuum absorption of vibrationally excited O2 from 200–320 nm

Cross sections for absorption from excited vibrational levels of the ground X³Σ^-_g state of molecular oxygen to the repulsive 1³Π_u state are given. The potential energy curve for the 1³Π_u state of O₂ is constructed to be consistent with predissociation data for the B³Σ^-u state and with recent ab initio calculations. In the photon wavelength range of 200–320 nm the cross sections are smoothly oscillatory and in no case larger than 1 × 10^-21 cm². In the region of the Schumann-Runge bands the cross sections are of order 0.4 × 10^-21 cm².     

Low-lying electronic states of CuN calculated by MRCI method

The high accuracy ab initio calculation method of multi-reference configuration interaction(MRCI) is used to compute the low-lying eight electronic states of CuN.The potential energy curves(PECs) of the X~3∑~-,1~3Π,2~3∑~-,1~3△,1~1△,1~1∑~-,1~1Π,and ~5∑~- in a range of R=0.1 nm-0.5 nm are obtained and they are goodly asymptotes to the Cu(~2S_g) + N(~4S_u) and Cu(~2S_g)+N(~2D_u) dissociation limits.All the possible vibrational levels,rotational constants,and spectral constants for the six bound states of X~3∑~-,1~3Π,2~3∑~-,1~1△,1~1∑~-,and 1~1 Π are obtained by solving the radial Schrdinger equation of nuclear motion with the Le Roy provided Level 8.0 program.Also the transition dipole moments from the ground state X~3∑~- to the excited states 1~3Π and 2~3∑~- are calculated and the result indicates that the 2~3∑-X~3∑ transition has a much higher transition dipole moment than the 1~3Π-X~3∑~- transition even though the l~3Π state is much lower in energy than the 2~3∑~- state.     

Pion-Rotational Nucleus Scattering and the Interacting Boson Model

A procedure of combining the medium energy scattering theory in the eikonal approximation with the interacting boson model (IBM) is proposed to study the pion-rotational nucleus scattering. The channel coupling effects in the excitation of nuclear collective state with π^- and π⁺ elastic and inelastic scattering are analyzed. The calculated cross sections for the excitation of 2₁⁺ state of ¹⁵²Sm agmree with the experimental data quite well.     

Pion-Nucleus Scattering and the Interacting Boson Model

A procedure of combining the medium energy scattering theory in the Eikonal approximation with the interacting boson model is proposed to study the pion-nucleus scattering. The channel coupling effects in the excitation of nuclear collective state with ρ^- and ρ⁺ elastic and inelastic scattering are analyzed. The calculated cross sections for the excitation of 2₁⁺ state of ²¹⁸Sn agree with experimental data quite well.     

Effects of a Family Non-universal Z' Boson in \bar{B}_d→μ+μ- and B- →π-μ+μ-,ρ-μ+μ- Decays

Motivated by the recently updated experimental measurement on \bar{B}_d→μ⁺μ^- and B^-→π^-μ⁺μ^- decays by CDF and Belle collaborations, we revisit these
decays, as well as B^-→ρ^-μ⁺μ^- decay, within the Standard Model, and evaluate the effects of a family non-universal Z' boson. Under the constraint from {\cal B}(B^-→π^-μ⁺μ^-), we find the ranges of the Z' couplings S^LR_μμ< -5.2×10^-2 or D^LR_μμ < -8.1× 10^-2 are excluded. Within the allowed Z' parameters spaces, comparing with the SM predictions, we find that {\cal B}(\bar{B}_d→ μ⁺μ^-, {\cal B}(B^-→ π^-μ⁺μ^-), and {\cal B}(B^-→ρ^-μ⁺μ^-) could be enhanced by a factor about
226%, 245%, and 254%, respectively, byZ' contributions. However, they are hardly to be reduced. Furthermore, the zero crossing in the normalized forward-backward asymmetry spectrum of B^- →ρ^-μ⁺μ^- decay at low dimuon mass always exists.     

Rigorous pion-pion scattering lengths from threshold πN → ππN data

A new evaluation of the universal ππ scattering length relation is used to extract the ππ s-wave scattering lengths from threshold pion production data. Previous work has shown that the chiral perturbation series relating threshold pion production to ππ scattering lengths appears to converge well only for the isospin-2 case, giving a₂ = −0.031 ± 0.007m_π⁻¹. A model-independent and data-insensitive universal curve then implies a₀ = 0.235 ± 0.03m_π⁻¹ for the isospin-0 scattering length.     

The Role of a1(1260) in π-p→a1-(1260)p and π-p→π-ρ0p Reactions Near Threshold

We report on a theoretical study of the π^-p→a₁^-(1260) p and π^-p→π^-ρ⁰p reactions near threshold within an effective Lagrangian approach. The production process is described by t-channel ρ⁰ meson exchange. For the π^-p→π^-ρ⁰p reaction, the final π^-ρ⁰ results from the decay of the a₁(1260) resonance, which is assumed as a dynamically generated state from the K^*K and ρπ coupled channel interactions. We calculate the total cross section of the π^-p→a₁^-(1260)p reaction. It is shown that, with the coupling constant of the a₁(1260) to ρπ channel obtained from the chiral unitary theory and a cut off parameter Λρ~1.5 GeV in the form factors, the experimental measurement can be reproduced. Furthermore, the total and differential cross sections of π^-p→a₁^-(1260)p→π^-ρ⁰p reaction are evaluated, and it is expected that our model calculations can be tested by future experiments. These reactions are important for the study of the a₁(1260) resonance and would provide further constraints on the properties of the a₁(1260) state.     

Spectroscopy of light Λ hypernuclei

We recently measured high-statistics and high-resolution spectra of p-shell Λ hypernuclei produced by the (π⁺, K⁺) reaction. In this article, cross sections and their angular distributions of _Λ¹²C and _Λ¹⁶O are reported. The obtained cross sections are well reproduced by DWIA calculations.     

Self energies of the pion and the Δ isobar from the He(e,e′π)H reaction

In a kinematically complete experiment at the Mainz microtron MAMI, pion angular distributions of the ³He(e,e′π⁺)³H reaction have been measured in the excitation region of the Δ resonance to determine the longitudinal (L), transverse (T), and the LT interference part of the differential cross section. The data are described only after introducing self-energy modifications of the pion and Δ-isobar propagators. Using Chiral Perturbation Theory (ChPT) to extrapolate the pion self energy as inferred from the measurement on the mass shell, we deduce a reduction of the π⁺ mass of MeV/c² in the neutron-rich nuclear medium at a density of fm⁻³. Our data are consistent with the Δ self energy determined from measurements of π⁰ photoproduction from ⁴He and heavier nuclei.     

Isobar doorway approach to pion scattering on open shell nuclei

Delta-hole approach developed for the pion scattering on closed shell nuclei is extended to be applied to the case of open shell nuclei. The doorway space is spanned by the states of the form |Ψ^(A−1)ψ^(Δ) which correspond to |Δ h states in the usual delta-hole approach for closed shell nuclei. In this approach, the effects of the couplings between elastic and inelastic channels are incorporated in a natural way. As a first application of this approach, some numerical calculations have been done for the elastic and inelastic pion scattering on ¹²C and the elastic scattering on ¹⁴N and ¹⁴C. The effects of the nuclear structure and the coupling between elastic and inelastic channels are discussed.     

THE SYMMETRIC STRUCTURE OF EXCITED STATES OF 13ΛC AND INVESTIGATIONS OF THE ANGULAR DISTRIBUTIONS OF 13C(K-,π-)13ΛC*

Based on the meth SU₃ × SU₂ supermultiplet classification,we studied the symmetric compon-ents of 10.4 and 16.4 MeV configuration of the ¹³_ΛC hypernucleus by calculating the hypernucleus by calculating the angular distribution of ¹³C(K^-,π^-)¹³_ΛC^* in the framework of DWIA, and analysed the effects of varying the parameters on the angular distributions.     

一氟化碳电子态的光谱性质和预解离机理的理论研究

采用考虑Davidson修正的内收缩多参考组态相互作用(icMRCI+Q)方法结合相关一致基组aug-cc-pV5Z和aug-cc-pV6Z首次计算了一氟化碳(CF)11个Λ-S 态(X²Π , a⁴Σ^-, A²Σ⁺, B²Δ, 1⁴Π, 1²Σ^-, 2⁴Π, 1^{4}Δ , 1⁴Σ⁺, 2²Σ^-和2⁴Σ^-) 所产生的25个Ω 态的势能曲线. 计算中考虑了旋轨耦合效应、核价相关和标量相对论修正以及将参考能和相关能分别外推至完全基组极限. 基于得到的势能曲线, 获得了束缚和准束缚的Λ-S态和Ω 态的光谱常数, 与已有的实验结果非常符合. 分析了束缚和准束缚的Λ-S态在各自平衡核间距R_e处的主要电子组态. 由于1⁴Π 和2⁴Π态的避免交叉, 发现准束缚态2⁴Π. 由Λ-S态势能曲线的交叉现象, 借助于计算的旋轨耦合矩阵元, 分析了a⁴Σ^-和B²Δ 态的预解离机理. 计算了25个Ω 态的离解关系, 给出了它们的离解极限. 最后研究了A²Σ⁺-X²Π 跃迁特性, 本文计算得到的A²Σ⁺-X²Π跃迁的Frank-Condon 因子和辐射寿命与已有实验值也符合得非常好.