  We investigate pion and sigma meson correlations in hot quark matter within a
modified NJL model. Special emphasis is on the transformation of mesonic bound
states to resonances (Mott dissociation) when due to the partial chiral
symmetry restoration with increasing temperature the threshold of
quark-antiquark continuum states drops below the meson mass at the
corresponding Mott temperature. The description is based on evaluating the
polarization functions for quark-antiquark (meson) correlations as a function
of the temperature and the results can be represented by introducing modulus
and phase of the complex propagator functions for the mesonic states. We study
the effect of modelling confinement by introducing a low-momentum cutoff in
loop integrals. We make the ansatz that this cutoff is identified with the
dynamically generated quark mass gap and find an increase of the continuum
threshold which makes the otherwise unbound sigma meson a bound state in the
vacuum. We discuss the in-medium behavior of the mesonic phase shifts including
the Mott effect and find accordance with the Levinson theorem.
