The Search for New Physics in D^0 --> gamma gamma Decay

Abstract

We present main results of the investigation of the rare decay mode D^0 -->gamma gamma, in which the long distance contributions are expected to be dominant. Using the Heavy Quark Chiral Lagrangian we have considered the anomaly contribution which relates to the annihilation part of the weak Lagrangian and the one - loop pi, K diagrams. The loop contributions which are proportional to g and contain the a_1 Wilson coefficient are found to dominate the decay amplitude. The branching ratio is then calculated to be (1.0+-0.5)x 10^{-8}. Observation of an order of magnitude larger branching ratio could signal new physics.