The Angular Observables of $Λ_b \to Λ_c(\to Λ^0 π^+) \, τ^-(\to π^- ν_τ)\, \barν_τ$ within the Paradigm of FCCC Anomalies
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arXiv
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| Format: | Preprint |
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2026
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| _version_ | 1866915980679053312 |
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| author | Arslan, Muhammad Ahmed, Ishtiaq Aslam, Muhammad Jamil |
| author_facet | Arslan, Muhammad Ahmed, Ishtiaq Aslam, Muhammad Jamil |
| contents | We present a global analysis of the current $B$-meson flavor anomalies and extend it to the baryonic sector through the decay $Λ_b^0 \to Λ_c^+(\to Λ^0 π^+) τ^-(\to π^- ν_τ)\barν_τ$. The lepton flavor universality ratios $R_{τ/(μ,e)}(D^{(*)})$, measured by BaBar, Belle, and LHCb, exhibit a combined $3.8σ$ deviation from Standard Model (SM) predictions. Using the latest HFLAV averages and $B_c$-lifetime constraints, $\mathcal{B}(B_c \to τν) < 60\%, 30\%, 10\%$, found new physics (NP) solutions to the cascade decay $Λ_b^0 \to Λ_c^+(\to Λ^0 π^+) τ^-(\to π^- ν_τ)\barν_τ$. The scenario $(C_{V_L},C_{S_R})$ emerges as the most favored NP solution, largest pull from the SM and insensitive to branching-ratio constraints; followed by $C_{V_L}$ case. We study the impact of NP operators on a complete set of angular observables on the five-fold $Λ_b$ decay using Lattice-QCD form factors and find that the scenarios $(\Re[C_{S_L}=4C_T],\Im[C_{S_L}=4C_T])$ and $(C_{S_L},C_{S_R})$ generate the largest deviations from the SM predictions. In particular, the observables $\mathcal{K}_{1c}$, $\mathcal{K}_{2ss}$, $\mathcal{K}_{2cc}$, and $\mathcal{K}_{4s}$ show the highest sensitivity to NP effects. The correlation analysis reveals the $(\Re[C_{S_L}=4C_T],\Im[C_{S_L}=4C_T])$ scenario exhibits inverse correlations among $\mathcal{K}_{1c}$ and $\mathcal{K}_{2ss,2cc,4s}$ and direct correlations between $\mathcal{K}_{2ss}$ and $\mathcal{K}_{2cc,4s}$, pointing to a possible CP-violating phase, while the $(C_{S_L},C_{S_R})$ scenario displays complementary behavior consistent with CP-conserving dynamics. These results establish baryonic semileptonic decays as a powerful and independent probe of the $R_{τ/(μ,e)}(D^{(*)})$ anomalies, with future measurements providing critical tests of the underlying NP structure. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2604_24922 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | The Angular Observables of $Λ_b \to Λ_c(\to Λ^0 π^+) \, τ^-(\to π^- ν_τ)\, \barν_τ$ within the Paradigm of FCCC Anomalies Arslan, Muhammad Ahmed, Ishtiaq Aslam, Muhammad Jamil High Energy Physics - Phenomenology High Energy Physics - Experiment High Energy Physics - Lattice We present a global analysis of the current $B$-meson flavor anomalies and extend it to the baryonic sector through the decay $Λ_b^0 \to Λ_c^+(\to Λ^0 π^+) τ^-(\to π^- ν_τ)\barν_τ$. The lepton flavor universality ratios $R_{τ/(μ,e)}(D^{(*)})$, measured by BaBar, Belle, and LHCb, exhibit a combined $3.8σ$ deviation from Standard Model (SM) predictions. Using the latest HFLAV averages and $B_c$-lifetime constraints, $\mathcal{B}(B_c \to τν) < 60\%, 30\%, 10\%$, found new physics (NP) solutions to the cascade decay $Λ_b^0 \to Λ_c^+(\to Λ^0 π^+) τ^-(\to π^- ν_τ)\barν_τ$. The scenario $(C_{V_L},C_{S_R})$ emerges as the most favored NP solution, largest pull from the SM and insensitive to branching-ratio constraints; followed by $C_{V_L}$ case. We study the impact of NP operators on a complete set of angular observables on the five-fold $Λ_b$ decay using Lattice-QCD form factors and find that the scenarios $(\Re[C_{S_L}=4C_T],\Im[C_{S_L}=4C_T])$ and $(C_{S_L},C_{S_R})$ generate the largest deviations from the SM predictions. In particular, the observables $\mathcal{K}_{1c}$, $\mathcal{K}_{2ss}$, $\mathcal{K}_{2cc}$, and $\mathcal{K}_{4s}$ show the highest sensitivity to NP effects. The correlation analysis reveals the $(\Re[C_{S_L}=4C_T],\Im[C_{S_L}=4C_T])$ scenario exhibits inverse correlations among $\mathcal{K}_{1c}$ and $\mathcal{K}_{2ss,2cc,4s}$ and direct correlations between $\mathcal{K}_{2ss}$ and $\mathcal{K}_{2cc,4s}$, pointing to a possible CP-violating phase, while the $(C_{S_L},C_{S_R})$ scenario displays complementary behavior consistent with CP-conserving dynamics. These results establish baryonic semileptonic decays as a powerful and independent probe of the $R_{τ/(μ,e)}(D^{(*)})$ anomalies, with future measurements providing critical tests of the underlying NP structure. |
| title | The Angular Observables of $Λ_b \to Λ_c(\to Λ^0 π^+) \, τ^-(\to π^- ν_τ)\, \barν_τ$ within the Paradigm of FCCC Anomalies |
| topic | High Energy Physics - Phenomenology High Energy Physics - Experiment High Energy Physics - Lattice |
| url | https://arxiv.org/abs/2604.24922 |