2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/203491We compute the third-order correction to the heavy-quark current correlation function due to the emission and absorption of an ultrasoft gluon. Our result supplies a missing contribution to top-quark pair production near threshold and the determination of the bottom quark mass from QCD sum rules.10 pages, LaTeXHigh Energy Physics - Phenomenologytext