The regular semisimple locus of the affine quotient of the cotangent bundle of the Grothendieck-Springer resolution

Let G=GLn(C), the general linear group over the complex numbers, and let B be the set of invertible upper triangular matrices in G. Let b=Lie(B). For μ:T∗(b×Cn)→b∗, where b∗≅g∕u and u being strictly upper triangular matrices in g=Lie(G), we prove that the Hamiltonian reduction μ−1(0)rss∕∕B of the extended regular semisimple locus brss of the Borel subalgebra is smooth, affine, reduced, and scheme-theoretically isomorphic to a dense open locus of C2n. We also show that the B-invariant functions on the regular semisimple locus of the Hamiltonian reduction of b×Cn arise as the trace of a certain product of matrices.