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We present a calculation of the rare decay modes D 0 → e + e − γ and D 0 → µ + µ − γ in the framework of Standard Model. For the short distance part, we have derived QCD corrections to the Wilson coefficients involved, including C 9 . The latter is found to be strongly suppressed by the corrections, leading to diminished values for the c → ul + l − branching ratios in the 10 −10 range. Within SM the exclusive decays are dominated by long distance effects. Nonresonant contributions are estimated using heavy quark and chiral symmetries to be at the level of 10%, compared to the contributions arising from D 0 → V γ → l + l − γ, with V = ρ, ω, φ. The total SM branching ratio is predicted to be in the range (1 − 3) × 10 −9 . We also consider contributions coming from MSSM with and without R parity conservation. Effects from MSSM are significant only for the R-parity violating case. Such contributions enhance the branching ratio D 0 → µ + µ − γ to 0.5×10 −7 , based on appropriately allowed values for C 9 and C 10 . This selects D 0 → µ + µ − γ as a possible probe of new physics.PACS numbers: 13.25.Ft, 12.60.Jv,

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