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arXiv 1106.0740hep-ph
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b-重子衰变的离散对称性分析

Analysis of Discrete Symmetries in b-Baryon Decays

Aqeel Ahmed

摘要:

用运动学和动力学分析相结合的方法研究了衰变道Lambda_{b} --> λ V,其中V是矢量介子(1^-).在运动学方面,我们采用了螺旋度理论,而在动力学方面,我们采用重夸克有效理论(HQET)计算了重子Lambda_{b}和λ之间的强子矩阵元。计算了Lambda_{b} --> λ J/psi、Lambda_{b}--> λ ρ ^0和Lambda_{b}--> λ ω的分支比(BR)和螺旋度不对称参数(alpha_{AS})。由于这两种衰变产物都是极化的,所以它们提供了有趣的机会来进行时间反演、CP破坏和CPT不变性的测试。通过自旋密度矩阵的角分布,极化和一些极化相关的衰变产物的模型无关的参数化。极化的横向分量和两个极化相关对时间反转破坏敏感。此外,几个CP-和CPT-奇观测量指出。

英文摘要:

A study of the decay channels Lambda_{b}-->Lambda V, where V is a vector meson (1^-), has been done by putting together kinematical and dynamical analysis. An intensive use of the helicity formalism is involved on the kinematical side, while on the dynamical side, Heavy Quark Effective Theory (HQET) is applied to calculate the hadronic matrix elements between the baryons Lambda_{b} and Lambda. The branching ratios(BR) and helicity asymmetry parameters (alpha_{AS}) for Lambda_{b} --> Lambda J/psi, Lambda_{b} --> Lambda rho^0 and Lambda_{b} --> Lambda omega have been calculated. Since both the decay products are polarized, so they offer interesting opportunities to perform tests of time reversal, CP violation and of CPT invariance. A model independent parametrization is done via spin density matrix of the angular distribution, polarizations and some of polarization correlations of the decay products. The transverse component of the polarization and two polarization correlations are sensitive to time reversal violations. Moreover several CP- and CPT-odd observables are pointed out.

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