Polarizability contribution to the energy levels of the muonic helium $(\mu^{4}He)^{+}$

An experiment measuring the 2S-2P separation in the ion ( mu /sup 4 /He)/sup +/ is in progress at CERN. Comparison of the outcome of this experiment with the prediction of quantum electrodynamics requires the knowledge of the hadronic correction due to the two-photon exchange mechanism. Therefore, the authors have calculated the correction to the energy levels of the ion ( mu /sup 4/He)/sup +/ due to this mechanism. The hadronic contribution to the 2S-2P separation is found to be approximately 16 AA which is about three times larger than the expected experimental uncertainty. (12 refs).