arXiv 0905.14252009-05-09hep-ph

新粒子态的质量测定

Mass Determination of New Particle States

Mario Serna

备注：: Oxford D.Phil Thesis. Defended Sept 2008. Awarded March 2009. 150 pg

摘要：

我们研究新粒子态的质量测定的理论和实验方面。假设超对称性，我们更新夸克和轻子质量矩阵在大统一尺度占阈值校正增强大tan β。从夸克和轻子质量满足一些大统一理论（GUTs）中提出的一组经典关系的假设，我们预测tan β需要很大，并且胶子的软质量需要与wino的软质量具有相反的符号。在即将到来的强子对撞机上，现有的测量胶子质量相位的工具需要独立于模型的运动学技术来确定新的超对称粒子态的质量。我们讨论了目前的技术来确定不可见粒子的质量。我们回顾了横向质量运动变量M_{T2}和使用不变质量的边缘，找到群众之间的关系。接下来，我们介绍了一种新的技术，在对称衰变链的不同阶段使用M_{T2}在新粒子态的质量之间添加额外的约束。这些新的关系进一步限制了新粒子状态之间的质量差异，但仍然使绝对质量难以确定。接下来，我们引入受约束的质量变量M_{2C,LB}、M_{2C,UB}、M_{3C,LB}、M_{3C,UB}，以在给定质量差异的情况下为质量标度提供逐个事件的下限和上限。我们证明了质量尺度的确定在现实的情况下，超对称模型的模拟数据拟合理想分布的研究。我们的结论是，在这篇论文中介绍的技术具有竞争力的精度和准确性，甚至超过最知名的技术在强子对撞机的不可见粒子的质量测定。

英文摘要：

We study theoretical and experimental facets of mass determination of new particle states. Assuming supersymmetry, we update the quark and lepton mass matrices at the grand unification scale accounting for threshold corrections enhanced by large tan beta. From the hypothesis that quark and lepton masses satisfy a classic set of relationships suggested in some Grand Unified Theories (GUTs), we predict tan beta needs to be large, and the gluino's soft mass needs to have the opposite sign to the wino's soft mass. Existing tools to measure the phase of the gluino's mass at upcoming hadron colliders require model-independent, kinematic techniques to determine the masses of the new supersymmetric particle states. We discuss the current techniques to determine the mass of invisible particles. We review the transverse mass kinematic variable M_{T2} and the use of invariant-mass edges to find relationships between masses. Next, we introduce a new technique to add additional constraints between the masses of new particle states using M_{T2} at different stages in a symmetric decay chain. These new relationships further constrain the mass differences between new particle states, but still leave the absolute mass weakly determined. Next, we introduce the constrained mass variables M_{2C,LB}, M_{2C,UB}, M_{3C,LB}, M_{3C,UB} to provide event-by-event lower-bounds and upper-bounds to the mass scale given mass differences. We demonstrate mass scale determination in realistic case studies of supersymmetry models by fitting ideal distributions to simulated data. We conclude that the techniques introduced in this thesis have precision and accuracy that rival or exceed the best known techniques for invisible-particle mass-determination at hadron colliders.

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英文摘要：

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