Dynamical mass generation by source inversion: Calculating the mass gap of the chiral Gross-Neveu model

We probe the $U\left(N\right)\mathrm{}$ chiral Gross-Neveu model with a source term $J\overline{\Psi }\Psi .$ We find an expression for the renormalization scheme and scale invariant source $Ĵ,$ as a function of the generated mass gap. The expansion of this function is organized in such a way that all scheme and scale dependence is reduced to one single parameter d. We obtain a nonperturbative mass gap as the solution of $Ĵ=0.\mathrm{}$ A physical choice for d gives good results for $N>\mathrm{}2.\mathrm{}$ The self-consistent minimal sensitivity condition gives a slight improvement.