The long-distance contribution of heavy B and D mesons are calculated in the light cone QCD sum rule. Here I have discussed both the parity conserving and parity violating form factors in the radiative decays of B and D mesons e.g. B*, B**, [Formula: see text], D*, D** and [Formula: see text] mesons. I have studied the decay of type P → Vγ and estimated the light cone QCD sum rule form factors and the branching ratio for various decay modes of B and D mesons. Although the short-distance electromagnetic Penguin contribution is the dominant contribution in the P → Vγ decay, it is also necessary to take into account the long distance contribution for completeness of study of the decays discussed in the text.
Improved Light-Cone QCD Sum Rule Analysis of Rare Decays Λ
b
→ Λγ and Λ
b
→ Λ
l
+
l
−