The Study Of CP Violation Phenpmenon On Higgs Decay Process

The standard model of particle physics (Standard Model, SM) has described the elementary particles which composites of material and the interaction between them. In the past few decades, many theoretical predictions of the standard model have been confirmed by the high energy physics experiment. In 2012, at the Large Hadron Collider (LHC) people have found the particle named Higgs who played a key role in the standard model, then the standard model has become the most perfect normative theory so far. But the experiment haven’t determined the properties of Higgs which is the combination of charge conjugation with parity (CP) in the standard model. The conservation of CP transformation is violated slightly when particle decays through weak interaction. People call this kind of phenomenon CP violation. In this paper, we use the mixed angle φ of different CP eigenstates (it is called CP mixing angle here) to determine the CP properties of Higgs particles by studying Higgs decays to τ-τ+ process. CP mixing angle φ reflects the extent of CP violation. Our study is helpful to study the CP properties of Higgs and provide valuable method to search for new physics beyond the standard model, and it is of great significance.We has considered four body final states decay mode of Higgs:H�'τ-+τ+�' a+b+vτ+vτ (where a and b denote π or ρ). Nine observables are constructed by using the momentum of τ、π and p in the subsequent τ-lepton decays τ�'πvτ and τ�'ρvτ. We have taken two different kinds of numerical distribution into consideration:differential decay width varies as observables and asymmetry varies as CP mixing angle φ. According to the result of numerical simulation, we can come to the conclusion:1, when the first type of distribution is applied, the φcp is the best observable to distinguish the extent of CP violation.2, the new defined distribution that asymmetry varies as CP mixing angle φ is applicable to any of the nine observables, it means that the new distribution is more universal. Observables φ、 cos φab、φm could obtain one-to-one correspondences between asymmetry and CP mixing angle φ. The character which could always obtain quantitative result on distinguishing the extent of CP violation has more advantages.