Need for the intensity-dependent pion-nucleon coupling in multipion production processes

We give reasons in support of the use of an effective intensity-dependent pion-nucleon coupling Hamiltonian for describing the properties of the pion multiplicity distribution and the corresponding factorial moments within the thermal-density matrix approach.We explain the appearance of the negative-binomial (NB) distribution for pions and the well-known empi- rical relation of Wroblewski.Our model Hamiltonian is written as a linear combination of the generators of the SU(1,1) group.We find the generating function for the pion multiplicity distribution at finite temperature T and discuss the properties of the second-order factorial moment.Also, we show that an intensity-dependent pion-nucleon coupling generates the squeezed states of the pion field. At T=0, these squeezed states become an inherent property of the NB distribution.