Two-body Cabibbo-suppressed Decays of Charmed Baryons into Vector Mesons and into Photons

The heavy quark effective theory and the factorization approximation are used to treat the Cabibbo-suppressed decays of charmed baryons to vector mesons, $\Lambda_C\rightarrow p{\rho^0}, p\omega$, $\Xi_C^{+,0}\rightarrow\Sigma^{+,0}\phi, \Sigma^{+,0}{\rho^0}, \Sigma^{+,0}\omega$ and $\Xi_C^{0}\rightarrow\Lambda\phi, \Lambda\rho, \Lambda\omega$. The input from two recent experimental results on $\Lambda_C$ decays allows the estimation of the branching ratios for these modes, which turn out to be between $10^{-4}$ and $10^{-3}$. The long distance contribution of these transitions via vector meson dominance to the radiative weak processes $\Lambda_C\rightarrow p\gamma$, $\Xi_C\rightarrow\Sigma\gamma$ and $\Xi_C^0\rightarrow\Lambda\gamma$ leads to quite small branching ratios, $10^{-6}-10^{-9}$; the larger value holds if a sum rule between the coupling constants of the vector mesons is broken.