$CP$ violation in two-body hadronic $Λ_b$ decays in the PQCD approach
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| Format: | Preprint |
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2025
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| _version_ | 1866918162242469888 |
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| author | Han, Jia-Jie Yu, Ji-Xin Li, Ya Li, Hsiang-nan Wang, Jian-Peng Xiao, Zhen-Jun Yu, Fu-Sheng |
| author_facet | Han, Jia-Jie Yu, Ji-Xin Li, Ya Li, Hsiang-nan Wang, Jian-Peng Xiao, Zhen-Jun Yu, Fu-Sheng |
| contents | We systematically investigate the $CP$-averaged branching ratios and $CP$ violations (CPVs) for the two-body hadronic decays $Λ_b\to ph$, where $h$ runs through the mesons $π^-$, $ρ^-$, $a_1^-(1260)$, $K^-$, $K^{\ast -}$, $K_1^-(1270)$ and $K_1^-(1400)$, in the perturbative QCD approach to order $α_s^2$ in the strong coupling. Various topological amplitudes are obtained by incorporating subleading-twist hadron distribution amplitudes, which exhibit reasonable hierarchical patterns, sizable strong phases, and non-negligible higher-power corrections. The predicted direct CPVs in $Λ_b\to pπ^-,pK^-$, different from those in similar $B$ meson decays, are as small as the current data. The low CPV in $Λ_b\to pπ^-$ results from the cancellation between the $S$- and $P$-wave CPVs, while the one in $Λ_b\to pK^-$ is determined by the tiny $S$-wave CPV. However, individual partial-wave CPVs can exceed $10\%$, consistent with direct CPVs in $B$ meson decays. The CPVs in the $Λ_b\to pK_1^-(1270),pK_1^-(1400)$ channels are relatively larger. In particular, CPVs above $20\%$ appear in the up-down asymmetries associated with the final-state angular distributions of $Λ_b\to pK_1^-(1270),pK_1^-(1400)$, followed by the secondary $K_1\to Kππ$ decays. These observables offer promising prospects for firmly establishing baryon CPVs. The decay asymmetry parameters of $Λ_b\to ph$ are also predicted for future experimental confrontations. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2506_07197 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | $CP$ violation in two-body hadronic $Λ_b$ decays in the PQCD approach Han, Jia-Jie Yu, Ji-Xin Li, Ya Li, Hsiang-nan Wang, Jian-Peng Xiao, Zhen-Jun Yu, Fu-Sheng High Energy Physics - Phenomenology High Energy Physics - Experiment We systematically investigate the $CP$-averaged branching ratios and $CP$ violations (CPVs) for the two-body hadronic decays $Λ_b\to ph$, where $h$ runs through the mesons $π^-$, $ρ^-$, $a_1^-(1260)$, $K^-$, $K^{\ast -}$, $K_1^-(1270)$ and $K_1^-(1400)$, in the perturbative QCD approach to order $α_s^2$ in the strong coupling. Various topological amplitudes are obtained by incorporating subleading-twist hadron distribution amplitudes, which exhibit reasonable hierarchical patterns, sizable strong phases, and non-negligible higher-power corrections. The predicted direct CPVs in $Λ_b\to pπ^-,pK^-$, different from those in similar $B$ meson decays, are as small as the current data. The low CPV in $Λ_b\to pπ^-$ results from the cancellation between the $S$- and $P$-wave CPVs, while the one in $Λ_b\to pK^-$ is determined by the tiny $S$-wave CPV. However, individual partial-wave CPVs can exceed $10\%$, consistent with direct CPVs in $B$ meson decays. The CPVs in the $Λ_b\to pK_1^-(1270),pK_1^-(1400)$ channels are relatively larger. In particular, CPVs above $20\%$ appear in the up-down asymmetries associated with the final-state angular distributions of $Λ_b\to pK_1^-(1270),pK_1^-(1400)$, followed by the secondary $K_1\to Kππ$ decays. These observables offer promising prospects for firmly establishing baryon CPVs. The decay asymmetry parameters of $Λ_b\to ph$ are also predicted for future experimental confrontations. |
| title | $CP$ violation in two-body hadronic $Λ_b$ decays in the PQCD approach |
| topic | High Energy Physics - Phenomenology High Energy Physics - Experiment |
| url | https://arxiv.org/abs/2506.07197 |