and velocity of one of the nucleons, the total energy of the pair and the relative angle.[]{data-label="simulation-NN"}](figNN-Etot.ps "fig:"){width="36.00000%"}\
![Simulation of $NN$ pairs emitted in decays of $\eta$-mesic nuclei. Shown are distributions over the kinetic energy and velocity of one of the nucleons, the total energy of the pair and the relative angle.[]{data-label="simulation-NN"}](figNN-bN.ps "fig:"){width="36.00000%"} ![Simulation of $NN$ pairs emitted in decays of $\eta$-mesic nuclei. Shown are distributions over the kinetic energy and velocity of one of the nucleons, the total energy of the pair and the relative angle.[]{data-label="simulation-NN"}](figNN-costheta.ps "fig:"){width="36.00000%"}

Neglecting binding effects and effects of Fermi motion of nucleons and $\eta$, we have the following kinematical characteristics of the correlated $NN$ pairs (i.e. energies, momenta, velocities) ejected in $\eta$-mesic nuclei decays: E\_[N\_1]{}\^[kin]{} = E\_[N\_2]{}\^[kin]{} = 12 m\_= 274 [MeV]{}, p\_[N\_1]{} = p\_[N\_2]{} = 767 [MeV]{}/c, \_[N\_1]{} = \_[N\_2]{} = 0.63. \[kinema-NN\] Actually, the Fermi motion and binding leads to fluctuations around these ideal parameters as a simple simulation reveals, see Fig. \[simulation-NN\]. Note that the angular correlation in the $NN$ pairs is stronger than that in the $\pi N$ pairs — owing to higher momenta of particles in $NN$.

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