Gaiotto and Witten found that one can construct 3d \( \mathcal{N} \) = 4 Chern-Simons matter theories by using \( \mathcal{N} \) = 4 SCFT whose momentum map of global symmetries satisfy special condition. Usually, one uses free hypermultiplet and twisted hypermultiplet, and more recently it was found that strongly coupled theory such as 3d version of TN theory and Argyres-Douglas matter can also be used. In this paper, we compute the superconformal index of these \( \mathcal{N} \) = 4 theories and derive the Coulomb/Higgs limit. Our results determine the moduli space of vacua, which is used to check various interesting mirror symmetry involving CSM theory and usual \( \mathcal{N} \) = 4 gauge theory.
