Title: Unitarity in gauge symmetry breaking on orbifold Show Chinese title

Title: 规范对称性破缺中的幺正性

Abstract: We study the unitarity bounds of the scattering amplitudes in the extra dimensional gauge theory where the gauge symmetry is broken by the boundary condition. The estimation of the amplitude of the diagram including four massive gauge bosons in the external lines shows that the asymptotic power behavior of the amplitude is canceled. The calculation will be done in the 5 dimensional standard model and the SU(5) grand unified theory, whose 5th dimensional coordinate is compactified on $S^1/Z_2$. The broken gauge theories through the orbifolding preserve the unitarity at high energies similarly to the broken gauge theories where the gauge bosons obtain their masses through the Higgs mechanism. We show that the contributions of the Kaluza-Klein states play a crucial role in conserving the unitarity. Show Chinese abstract

Abstract: 我们研究了在通过边界条件破缺规范对称性的额外维规范理论中散射振幅的单位性界限。 包含外部线路上四个大质量规范玻色子的图的振幅估计表明，振幅的渐近幂次行为被抵消。 计算将在五维标准模型和SU(5)大统一理论中进行，其第五维坐标被紧致化在$S^1/Z_2$上。 通过轨道折叠破缺的规范理论在高能下保持单位性，类似于通过希格斯机制获得规范玻色子质量的破缺规范理论。 我们表明，Kaluza-Klein态的贡献在保持单位性中起着关键作用。