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Rare radiative decays of charm baryons

We study weak radiative $|Δc|=|Δu|=1$ decays of the charmed anti-triplett ($Λ_c$, $Ξ_c^{+}$, $Ξ_c^{0}$) and sextet ($Σ_c^{++}$, $Σ_c^+$, $Σ_c^0$, $Ξ_c^{\prime +}$, $Ξ_c^{\prime 0}$, $Ω_c$) baryons in the standard model (SM) and beyond. We work out $SU(2)$ and $SU(3)_F$-symmetry relations. We propose to study self-analyzing decay chains such as $Ξ_c^+ \to Σ^+ (\to p π^0) γ$ and $Ξ_c^0 \to Λ(\to p π^-) γ$, which enable new physics sensitive polarization studies. SM contributions can be controlled by corresponding analysis of the Cabibbo-favored decays $Λ_c^+ \to Σ^+ (\to p π^0) γ$ and $Ξ_c^0 \to Ξ^0 (\to Λπ^0) γ$. Further tests of the SM are available with initially polarized baryons including $Λ_c \to p γ$ together with $Λ_c \to Σ^+ γ$ decays, or $Ω_c \to Ξ^0 γ$ together with $Ω_c \to (Λ,Σ^0) γ$. In addition, CP-violating new physics contributions to dipole operators can enhance CP-asymmetries up to few percent.