  We investigate screening masses at both sides of the first order finite
temperature transition with 3 quark flavors using the nonperturbatively
improved clover fermion action and the Iwasaki gauge action. We have developed
the method of hierarchical truncations with stochastic probing to accelerate
the noise estimator for evaluating quark loops at every spatial lattice slices.
At parameter values we study, the flavor singlet scalar meson has a screening
mass about half of the pion screening mass. It becomes lighter as the system
approaches the critical endpoint.
