Heavy Quark Production in the ACOT Scheme beyond NLO
  We compute the structure functions F2 and FL in the ACOT scheme for heavy quark production. We use the complete ACOT results to NLO, and make use of the MSbar massless results at NNLO and N3LO to estimate the higher order mass-dependent corrections. We show numerically that the dominant heavy quark mass effects can be taken into account using massless Wilson coefficients together with an appropriate rescaling prescription. Combining the exact NLO ACOT scheme with these expressions should provide a good approximation to the full calculation in the ACOT scheme at NNLO and N3LO. 
T. Stavreva, F. I. Olness, I. Schienbein, T. Jezo, A. Kusina, K.   Kovarik, J. Y. Yu
hep-ph