Two-loop BSM contributions to Higgs pair production in the aligned THDM

We study the impact of the two-loop corrections controlled by the BSM Higgs couplings on the cross section for the production of a pair of SM-like Higgs bosons via gluon fusion in the aligned THDM. To this aim, we reassess the two-loop calculation of ${\lambda }_{hhh}$, we compute for the first time the two-loop corrections to ${\lambda }_{hhH}$, and we include the relevant corrections to the Higgs-gluon couplings and to the s-channel propagators entering the $gg\to hh$ amplitude. We discuss the numerical impact of the two-loop BSM contributions, first on the individual couplings and then on the prediction for the pair-production cross section, in two benchmark scenarios for the aligned THDM.