Testing Physics Beyond the Standard Model at Linear Colliders

1.我们研究了超对称中电荷的三体衰变，并考察了分支比与标量夸克和轻子质量的关系。我们发现，当电荷为高介子时，电子分支比和陶子分支比的比值会有较大的偏差。这种测量对于获得关于睡眠质量的信息是有用的，因此也是了解超对称破缺机制的关键。在规范介导的超对称破缺场景中，超粒子最终衰变为自旋为3/2的引力子。我们开发了一种计算包含自旋3/2粒子的过程的螺旋振幅的形式。计算了引力子处于初始或终态时的一些衰变过程。我们开发了一个计算代码，该代码生成程序来计算e^+e^-碰撞中超粒子产生过程（具有两个或三个体最终状态）的截面。研究了e^+e^-碰撞中胶子交换引起的最终态相互作用对顶产最终轻子能量和角分布的影响。由于这种影响，分布变化了10%。我们还计算了与顶部生产过程相关的QCD势的二阶修正。我们发现重整化群方程是在动量空间解还是在位形空间解，结果是不同的。这种模糊性给横截面带来6%的误差。我们将为强相互作用希格斯扇区开发的N/D方法应用于pipi散射，并发现了暗示sigma介子存在的结果。

1.We study three-body decays of charginos in supersymmetry and examine the dependence of the branching ratios on the mass of scalar quarks and leptons. We find that the ratio of electronic and tauonic branching ratio can have a large deviation from one if the chargino is gaugino-like. This measurement should be useful to obtain information on slepton masses and therefore a key to the mechanism of supersymmetry breaking.2.In the gauge mediated scenario of supersymmetry breaking, superparticles eventually decay to a gravitino, which has a spin 3/2. We develop a formalism to calculate helicity amplitudes for processes containing spin 3/2 particles. Some decay processes with a gravitino in the initial or final state are calculated.3.We develop a compute code which generates programs to calculate cross sections for superparticle production processes (with two or three body final states) in e^+e^- collisions.4.We study the effect of final state interaction due to gluon exchange on the energy and angular distributions of final leptons in top production in e^+e^- collisions. The distributions change by ten percent due to this effect. We also calculate the second order correction to the QCD potential which is related to the top production process. We find that the result changes according to whether the renormalization group equation is solved in the momentum or the configuration space. This ambiguity gives a 6% error to the cross section.5.We apply the N/D method developed for the strongly interacting Higgs sector to pipi scattering and find a result suggestive of the existence of the sigma meson.