The dependence of the emission size on the hadron mass

The size of the emission volume of pions and kaons, r_ππ and r_KK, were measured in the hadronic Z⁰ decays through the two-pion and two-kaon Bose-Einstein correlations near threshold. Recently the emitter size of the two identical baryons, ΛΛ(Λ + ̄Λ + ̄), was evaluated from the dependence of the fraction of the spin S = 1 state on the energy near threshold where it is affected by the Pauli exclusion principle. Here we show that the r dependence on the particle masses, namely the hierarchy r_ππ> r_KK > r_ΛΛ observed in the Z⁰ hadronic decays, is well described in terms of the Heisenberg uncertainty principle. A good description can also be obtained via the virial theorem when applied to a general QCD potential. Other available approaches are also discussed.