  Witten suggested that fixed-point theorems can be derived by the
supersymmetric sigma model on a Riemann manifold M with potential term induced
from Killing vector on M. One of the well-known fixed-point theorem is the Bott
residue formula which represents intersection number of Chern classes of
holomorphic vector bundles on a Kahler manifold M as sum of contributions from
fixed point sets of a holomorphic vector field K on M. In this paper, we derive
the Bott residue formula by using topological sigma model (A-model) that
describes dynamics of maps from CP^{1} to M, with potential term induced from
the vector field $K$. Our strategy is to restrict phase space of path integral
to maps homotopic to constant maps. As an effect of adding a potential term to
topological sigma model, we are forced to modify BRST symmetry of the original
topological sigma model. Our potential term and BRST symmetry are closely
related to the idea used in the paper by Beasley and Witten where potential
terms induced from holomorphic section of a holomorphic vector bundle and
corresponding supersymmetry are considered.
