Hi, I am working on D 0 →K+ K− for my school project. I looked for any similar subjects and essays, i could not find this specific decay, i could write the form factors and also effective hamiltonian by myself but unfortunately i have problem writing the equations for LCDA ( light cone distribution amplitude) ( not sure about what i write)and so amplitude equations because my final mesons are semi-scalar and not vector. would you please advise me if you have any sources or if you can help me in this regard? I know i have two diagrams for this decay, one tree and one penguin diagram so i should have 6 Wilson coefficient. But i do not know how to use them to write the final amplitude equation and not sure if i am doing correct. Any sources and help regarding this decay will be so helpful for me.