We investigate the spectrum of doubly charmed
tetraquark $T_{cc}$ with quantum number $I(J^P) = 0(1^+)$
using MILC's $N_f = 2+1+1$ HISQ gauge ensembles at two lattice
spacings. We have included diquark-antidiquark operator together
with molecular and scattering operators in our analysis and
varied both the heavy and light quark masses. We employ the
anisotropic Clover action for heavy quarks, and $O(a)$-improved
Wilson--Clover action for the light (up/down) quarks. In order
to handle the non-analyticity near the Left Hand Cut we use
modified L\"uscher's method when we are close to it.