The dependence of the emission size on the hadron mass

The size of the emission volume of pions and kaons, r(pi pi) and r(KK), wer e measured in the hadronic Z(0) decays through the two-pion and two-kaon Bo se-Einstein correlations near threshold. Recently the emitter size of the t wo identical baryons, Lambda Lambda (<(Lambda)over bar><(Lambda)over bar>), 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 pr inciple. Here we show that the r dependence on the particle masses, namely the hierarchy r(pi pi) > r(KK) > r(Lambda Lambda) observed in the Z(0) hadr onic decays, is well described in terms of the Heisenberg uncertainty princ iple. A good description can also be obtained via the virial theorem when a pplied to a general QCD potential. Other available approaches are also disc ussed. (C) 1999 Published by Elsevier Science B.V. All rights reserved.