  We study the jamming transition in a model of elastic particles under shear
at zero temperature. The key quantity is the relaxation time $\tau$ which is
obtained by stopping the shearing and letting energy and pressure decay to
zero. At many different densities and initial shear rates we do several such
relaxations to determine the average $\tau$. We establish that $\tau$ diverges
with the same exponent as the viscosity and determine another exponent from the
relation between $\tau$ and the coordination number. Though most of the
simulations are done for the model with dissipation due to the motion of
particles relative to an affinely shearing substrate (the RD$_0$ model), we
also examine the CD$_0$ model, where the dissipation is instead due to velocity
differences of disks in contact, and confirm that the above-mentioned exponent
is the same for these two models. We also consider finite size effects on both
$\tau$ and the coordination number.
