Effects of non-perturbatively improved dynamical fermions in UKQCD simulations

We present results for QCD with 2 degenerate flavours of quark using a non- perturbatively improved action on a lattice volume of 16(3) x 32 where the bare gauge, coupling and bare dynamical quark mass have been chosen to main tain a fixed physical lattice spacing and volume (1.71 fm). By comparing me asurements from these matched ensembles, including quenched ones, we find e vidence of dynamical quark effects on the short distance static potential, the scalar glueball mass and the topological susceptibility. There is littl e evidence of effects on the light hadron spectrum over the range of quark masses studied (m(pi)/m(rho) greater than or equal to 0.60).