Heavy-quark form factors are calculated at β0αs∼ 1 to all orders in αs at the first order in 1 / β0. Using the inversion relation generalized to vertex functions, we reduce the massive on-shell Feynman integral to the HQET one. This HQET vertex integral can be expressed via a 2F1 function; the nth term of its ε expansion is explicitly known. We confirm existing results for nlL-1αsL terms in the form factors (up to L= 3), and we present results for higher L.
- EXPANDING HYPERGEOMETRIC-FUNCTIONS