We take a step towards a complete NLO-QCD determination of the production of a pair of Higgs scalars in the MSSM. Exploiting a low-energy theorem that connects the Higgs-gluon interactions to the derivatives of the gluon self-energy, we obtain analytic results for the one- and two-loop squark contributions to Higgs pair production in the limit of vanishing external momenta. We find that the two-loop squark contributions can have non-negligible effects in MSSM scenarios with stop masses below the TeV scale. We also show how our results can be adapted to the case of Higgs pair production in the NMSSM.
Agostini, A., Degrassi, G., Gröber, R., & Slavich, P. (2016). NLO-QCD corrections to Higgs pair production in the MSSM. JOURNAL OF HIGH ENERGY PHYSICS, 2016(4) [10.1007/JHEP04(2016)106].