  A conserving T-matrix approximation is applied to the two-dimensional
attractive Hubbard model in the low-density regime. A set of self-consistent
equations is solved in the real-frequency domain to avoid the analytic
continuation procedure. By tuning the chemical potential the particle density
was varied in the limits 0.01 < n < 0.18. For the value of the attractive
potential U=8t the binding energy of pairs monotonically decreases with
increasing n, from its zero-density limit 2.3t and vanishes at a critical
density n=0.19. A pairing-induced pseudogap in the single-particle density of
states is found at low densities and temperatures.
