Symplectic rational homology ball fillings of Seifert fibered spaces

We characterize when some small Seifert fibered spaces can be the convex boundary of a symplectic rational homology ball and give strong restrictions for others to bound such manifolds. As part of this, we show that the only spherical $3$-manifolds that are the boundary of a symplectic rational homology ball are the lens spaces L(p²,pq-1) found by Lisca and give evidence for the Gompf conjecture that Brieskorn spheres do not bound Stein domains in C^2. We also find restrictions on Lagrangian disk fillings of some Legendrian knots in small Seifert fibered spaces.