2π→2K SCATTERING AND πK ELASTIC SCATTERING

The 2π→2K low energy scattering cross-section was obtained using the relation between field and current. The low energy πK elastic scattering cross-section and its scattering length were also obtained using cross symmetry.     

Determination of the branching ratiosΓ(K L→3π0)/Γ(K L→π+ - 0) andΓ(K L→3π0)/Γ(K L→πev)

Improved branching ratios were measured for theK _L3⁰ decay in a neutral beam at the CERN SPS with the NA31 detector:

π-核弹性和非弹性散射

本文用 Glauber 理论计算和分析了能量为260和280 MeV 的π^-12C 弹性和非弹性散射微分截面.与实验结果符合较好.     

QCD calculation of theB→π,K form factors

We calculate the form factors for the heavy-to-light transitionsB,K by means of QCD sum rules using andK light-cone wave functions. Higher twist contributions as well as gluonic corrections are taken into account. The sensitivity to the shape of the leading-twist wave functions and effects ofSU (3)-breaking are discussed. The results are compared with quark model predictions and with the results from QCD sum rules for three-point correlators.Work supported by the German Federal Ministry for Research and Technology under contract No. 05 6MU93P     

K s →π+π−γ: a laboratory for meson dynamics

We discuss the decayK _{s +–} in the framework of chiral perturbation theory. The direct emission in this decay can be an useful test of meson dynamics.     

π-N弹性散射的第二共振峰

本文基于由推广的Chew-Low(弹性散射)静止理论所导得的双介子近似下的分波方程,在略去交叉项的贡献后求得其近似解。由很快上升的介子产生截面计算了D_3/2道(T=1/2)弹性散射截面,定性和半定量地解释了π-N第二共振处弹性散射截面中峯的出现、性质、位置和大小。     

τ→π~±2π~0v结构函数的测量

首次对τ→π2π0v衰变的结构函数进行了模型无关的实验测量,并与KS模型、IMR模型和Feindt模型进行了比较,在误差范围内,三种理论模型与实验结果一致．与OPAL组测量的τ→3π±v道的结构函数相比,在0．5＜Q2＜2．75GeV2范围内未发现明显差异．     

S波Kπ散射以及动力学产生标量介子

考虑Kπ和Kη两个耦合道, 用手征幺正方法研究了S波Kπ散射. 结果表明, 只用一个参数, 1.2GeV以下的散射相移数据就可以得到很好的描述, 并且散射长度也和实验值符合很好. 此方法可以动力学产生标量介子κ, 并预言其质量和宽度分别大约是752MeV和594MeV. 可以定性地产生对应于K^*₀(1430)的标量介子.     

s波π-π散射

本文用链状近似从一个不可重正化的作用拉氏函数计算π-π的s波散射振幅。这个作用拉氏函数所给出的p波散射恰恰正是Frazer-Fulco由色散关系得出的解。我们的计算结果指出,s波散射振幅中含有两个新的参数,因为作用拉氏函数是不可重正化的,引进新的参数是无法避免的,我们所得到的s波截面是与实验一致的,最后还讨论了我们的方法和色散关系方法的联系。     

K~* production in the KN → Kπp reaction

We investigate the K^∗ production in the KN→Kπp reaction using the effective Lagrangian approach and the isobar model.To describe this reaction,we first take into account the contributions from the π,ρ and ω exchanges,as in previous studies.We find that although the experimental data can be generally described,there are some obvious discrepancies between the model and the experiments.To improve the model,we consider the contributions of the axial-vector meson and hyperon exchange.It is shown that a large contribution of the axial-vector meson exchange can significantly improve the results.This may indicate that the coupling of the axial-vector meson,e.g.a1(1260),is large in the KK^∗ channel.To verify our model,measurements of the angular distributions and spin density matrix elements of K^∗0 in the KLp→K^∗0p reaction would be helpful,and we make predictions for this reaction for a future comparison.     

低能π介子—核子散射和π介子-π介子作用

用色散关系讨论了低能π-N散射振幅T⁺的部分、指出对P_1/2波的散射,用CGLN公式计算的结果基本上即已符合实验,对于S波散射,用CGLN得的与实验值的符号都相反,且随q迅速增加而超过么正条件所允许的极限,经过分析指明不可能引入π-πS波作用来解决这个问题,而同时还能保持使P_1/2波与实验相符,但从“减去”(subtraction)一次的S波色散关系出发,则由此修改后的CGLN公式计算的结果就基本上与实验相符,而π-π作用看来对它们只起着细致的调节作用。     

低能K-π散射

本文用L.A.P.Balázs处理低能π-π散射问题的方法,计算了低能K-π散射问题。得到了K-π散射I=1/2的P波共振位置(S_R)^1/2=854MeV,半宽度[Г₁^1/2]/2=126MeV和过程π+π→K+K的振幅的唯象常数ξ=0.3μ^-2,共振位置与目前的实验符合较好。     

Rare Decay Process K→πvv^- in Three-Site Higgsless Model]

Rare decay processes K→πvv^- and KL→π^0vv^- are considered in the framework of three-site Higgsless model. The contributions of this new physics model to these two decay processes come from the new heavy gauge bosons and the correction terms for the couplings of the ordinary gauge bosons with fermions. Our numerical results show that the branching ratios of these two decay processes can be enhanced by 40% and 50% relative to those predicted by the standard model.     

On puzzles and non-puzzles in B→ππ,πK decays

Recently, we have seen interesting progress in the exploration of CP violation in B⁰ _d→π⁺π^-: the measurements of mixing-induced CP violation by the BaBar and Belle collaborations are now in good agreement with each other, whereas the picture of direct CP violation is still unclear. Using the branching ratio and direct CP asymmetry of B⁰ _d→π^-K⁺, this situation can be clarified. We predict , which favours the BaBar result, and we extract γ=(70.0^+3.8 _-4.3)^°, which agrees with the unitarity triangle fits. Extending our analysis to other B→πK modes and B⁰ _s→K⁺K^- with the help of the SU(3) flavour symmetry and plausible dynamical assumptions, we find that all observables with colour-suppressed electroweak penguin contributions are measured to be in excellent agreement with the standard model. As far as the ratios R_c,n of the charged and neutral B→πK branching ratios are concerned, which are sizeably affected by electroweak penguin contributions, our standard-model predictions have almost unchanged central values but significantly reduced errors. Since the new data have moved quite a bit towards these results, the “B→πK puzzle” for the CP conserving quantities has been significantly reduced. However, the mixing-induced CP violation of B⁰ _d→π⁰K_S does look puzzling; if confirmed by future measurements, this effect could be accommodated through a modified electroweak penguin sector with a large CP violating new-physics phase. Finally, we point out that the established difference between the direct CP asymmetries of B^±→π⁰K^± and B_d→π^∓K^± appears to be generated by hadronic and not by new physics.     

π-18O非弹性散射

我们在程函扭曲的DWIA框架下,用跃迁密度方法计算了230MeV的π到¹⁸O的2⁺（1.98MeV）激发态上的非弹性散射微分截面,分析了π^-和π⁺截面比,研究了中子半径的变化对微分截面的影响。我们的理论计算结果与实验符合较好。     

π介子和核子在低能的散射

本文讨论了经过減除的π-核子散射色散关系和通常拉格朗日描述及其重整化处理间的关系。指出一次減除可以解释为作用常数的重整化。我们用经过減除的色散关系处理了π-核子S波散射。计算结果指出,π介子和核子间的相互作用应该是赝矢型而不是赝标型的。     

π+p→Λ+π+K反应共振—近阈效应关联的研究

本文建议作π+p→Λ+π+K反应的实验,其中质心系总能量固定为1900MeV。在末态K介子动能0—90MeV的变化范围内,观察末态Λ-π共振和在∑πk道产生阈附近的近阈效应。通过共振-近阈效应关联和共振的角分布可以确定Y₁^*的自旋和Y₁^*,和∑之间的相对宇称。按照先处理T短阵的么正性,后处理解析性的思想,本文引入了T矩阵在道空间上的对角表象。在此基础上,提出了唯象描述近阈效应、共振现象和末态相互作用,特别是近阈效应和在阈附近共振的关联的一个新方法。并且应用这个方法,处理了所建议实验中的末态共振-近阈效应关联。 关键词：     

多次散射理论与高能pp弹性散射

本文用复合粒子间的Glauber多次散射理论来分析高能pp弹性散射。假定质子由三个层子组成。且在入射弹为硬球近似下,层子在质子中形成简单的高斯分布,给出了一次、二次、三次……等多次散射振幅。并用这个结果计算了E_p=200、280、1500GeV的弹性散射角分布。结果表明高能量下的pp弹性散射可以视为层子与层子之间多次相干散射的结果。