Estimates of exchange topological contributions andCP -violating observables inΛ_(b)→ Λ φdecay

• Main Authors: Rui, Zhou, Li, Jia-Ming, Zhang, Chao-Qi
• Format: Journal Article
• Language: English
• Published: 27.10.2022
• Subjects: Physics - High Energy Physics - Experiment; Physics - High Energy Physics - Phenomenology
• DOI: 10.48550/arxiv.2210.15357

Phys. Rev. D 107, 053009 (2023) The penguin-dominated two-body weak decay of$\Lambda_b\rightarrow \Lambda \phi$is studied based on the perturbative QCD approach. In addition to the penguin emission diagrams, the penguin exchange and$W$exchange ones are also accounted for. It is found that the penguin exchange contribution is in fact important and comparable to the penguin emission one, while the$W$exchange contribution is highly Cabibbo-Kobayashi-Maskawa (CKM) suppressed. The predicted branching ratio,$\mathcal{B}(\Lambda_b\rightarrow \Lambda \phi)=6.9^{+1.9+1.8}_{-2.0-1.6}\times10^{-6}$ , is larger than the previous theoretical estimates but in comparison with the data from Particle Data Group at the level of 1 standard deviation. We also explore some pertinent decay asymmetry parameters that characterize the angular decay distributions. The inclusion of the$W$exchange contribution provides the nonzero weak phase difference,consequently, allowing us to estimate the direct$CP$violation and true triple product asymmetries in the concerned process. The numerical results demonstrate that the direct$CP$violation is at the level of a few percent, and the true triple product asymmetries are also predicted to be tiny, of order$10^{-2}-10^{-4}$ . The observed small$CP$ -violating observables have shown no significant deviations from zero. Our predictions will be subject to stringent tests with precise data from LHCb in the future.