It is known that thermalization in a CFT corresponds to black hole formation in AdS space. For a system to thermalize it must interact. To address black hole formation in string theory we look for thermalization in the D1D5 CFT which has an AdS dual. Thermalization should occur through interactions caused by twist operators which deform the theory off of its free point. The twist operators can join and unjoin ‘strings’ in the CFT. No clear evidence of thermalization was identified at first order in the twist deformation. We therefore compute interactions at second order in the twist deformation with an initial excitation propagating on one of the strings. We consider transitions of the initial excitation to three lower energy excitations in the final state. This yields preliminary evidence for thermalization.