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 empirical relation of Wróblewski . 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. PACS number(s): 25.75.+r, 13.85.-t, 13.75 e-mail address: [email protected] e-mail address: [email protected]