Destruction of a metastable string by particle collisions

We calculate the probability of destruction of a metastable string by collisions of the Goldstone bosons, corresponding to the transverse waves on the string. We find a general formula that allows to determine the probability of the string breakup by a collision of arbitrary number of the bosons. We find that the destruction of a metastable string takes place only in collisions of even number of the bosons, and we explicitly calculate the energy dependence of such process in a two-particle collision for an arbitrary relation between the energy and the largest infrared scale in the problem, the length of the critical gap in the string.