  We investigate the possibility of gravitationally generated particle
production via the mechanism of nonminimal torsion--matter coupling. An
intriguing feature of this theory is that the divergence of the matter
energy--momentum tensor does not vanish identically. We explore the physical
and cosmological implications of the nonconservation of the energy--momentum
tensor by using the formalism of irreversible thermodynamics of open systems in
the presence of matter creation/annihilation. The particle creation rates,
pressure, and the expression of the comoving entropy are obtained in a
covariant formulation and discussed in detail. Applied together with the
gravitational field equations, the thermodynamics of open systems lead to a
generalization of the standard $\Lambda$CDM cosmological paradigm, in which the
particle creation rates and pressures are effectively considered as components
of the cosmological fluid energy--momentum tensor. We consider specific models,
and we show that cosmology with a torsion--matter coupling can almost perfectly
reproduce the $\Lambda$CDM scenario, while it additionally gives rise to
particle creation rates, creation pressures, and entropy generation through
gravitational matter production in both low and high redshift limits.
