Tensor Charge of the Nucleon in Lattice QCD

First results of lattice QCD simulation on the nucleon tensor-charge $\delta q$ are presented. From the quenched QCD simulations with the Wilson quark action at $\beta = 5.7$ on a 16$^3\times$ 20 lattice and on a $12^3\times 20$ lattice, we find (i) the connected part $\delta q_{con.}$ is determined with small statistical error, (ii) the disconnected part $\delta q_{dis.}$, which violates the OZI rule, is consistent with zero, and (iii) the flavor-singlet tensor charge $\delta \Sigma (\mu^2 = 2 {\rm GeV}^2) = \delta u + \delta d + \delta s$ takes 0.562(88) at $\beta=5.7$, which is in contrast with the flavor-singlet axial charge $\Delta \Sigma = 0.1-0.3$.