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 $\lambda_s = V_{cs}^* V_{us}$ from tree operators and sub-leading one proportional to $\lambda_b = V_{cb}^* V_{ub}$ from both penguin and tree contributions. The coexistence of these two amplitudes is essential for generating nonzero CP violation (CPV) effects. Since the $\lambda_b$ 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 $\lambda_b$ amplitude can be extracted. Using current experimental data, a conservative analysis yields $\lambda_b$ amplitudes can be as large as about $10\%$ of the corresponding tree amplitudes with a significance of $2.1\sigma$. In addition, the Lee-Yang parameters of these decays provide an independent probe of this elusive term. We further identify two golden decay channels, $\Xi_c^0 \to p K^-$ and $\Xi_c^0 \to \Sigma^+ \pi^-$, which are particularly well suited for experimental studies of CPV.