# When are decays into quarks kinematically possible?

Consider the decay of a particle, $X$, into two quarks $q_1$ and $q_2$. Naively one would expect such a decay to be kinematically possible if: $m_Xc^2 \ge m_{q_1}c^2+m_{q_2}c^2$ however, I think that such a relation is wrong and the correct statment is that we require: $m_Xc^2 \ge m_{H_1}c^2+m_{H_2}c^2$ where $m_{H_i}$ represents the mass of the lightest hadron containing the quark $q_i$. Is this correct and please can you explain either way. Also what happens if one of the quarks is a top quark?

Example

For example I would say that the $\tau$ lepton can't decay into $\nu_\tau \bar c d$ since the lightest meson with a $\bar c$ quark is heavier then the $\tau$ particle, although $m_c\lt m_\tau$.