  We consider Mirror Twin Higgs models in which the breaking of the global
symmetry is realized linearly. In this scenario, the radial mode in the Higgs
potential is present in the spectrum, and constitutes a second portal between
the twin and SM sectors. We show that a study of the properties of this
particle at colliders, when combined with precision measurements of the light
Higgs, can be used to overdetermine the form of the scalar potential, thereby
confirming that it possesses an enhanced global symmetry as dictated by the
Twin Higgs mechanism. We find that, although the reach of the LHC for this
state is limited, future linear colliders will be able to explore a significant
part of the preferred parameter space, allowing the possibility of directly
testing the Twin Higgs framework.
