Isospin restrictions on charge distributions in charmed-particle decays

The isospin properties of the semileptonic and nonleptonic charm-changing weak interactions lead to restrictions on the branching ratios of the different charge states that can occur in multi-particle decays of charmed particles. Upper and lower bounds imposed by isospin invariance on these ratios, and on the average number of charged decay products, are calculated for various charmed-particle decay modes. Simultaneous bounds on the branching ratios of two different charge distributions in the same decay mode, or in isospin-related decay modes, are presented. Branching ratios are also calculated under the statistical postulate that all the allowed invariant isospin channels contribute equally and incoherently in each decay mode