Decoding the Amplitude Pair with Distinct CPV Phases in Charmed Baryon Decays

In this Letter, we propose a strategy to extract information on the hierarchical amplitude pair in singly Cabibbo-suppressed (SCS) charmed baryon two-body decays, with a dominant amplitude proportional to $λ_s = V_{cs}^* V_{us}$ from tree operators and sub-leading one proportional to $λ_b = V_{cb}^* V_{ub}$ from both penguin and tree contributions. The coexistence of these two amplitudes is essential for generating nonzero CP violation (CPV) effects. Since the $λ_b$ amplitude is strongly suppressed, its experimental determination is highly challenging. However, by exploiting SU(3) flavor symmetry, which relates the well-measured Cabibbo-favored (CF) amplitudes to the SCS tree amplitudes, information on the $λ_b$ amplitude can be extracted. Using current experimental data, a conservative analysis yields $λ_b$ amplitudes can be as large as about $10\%$ of the corresponding tree amplitudes with a significance of $2.1σ$. In addition, the Lee-Yang parameters of these decays provide an independent probe of this elusive term. We further identify two golden decay channels, $Ξ_c^0 \to p K^-$ and $Ξ_c^0 \to Σ^+ π^-$, which are particularly well suited for experimental studies of CPV.

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