Constraints on background torsion field from K physics

We point out that a background torsion field will produce an effective potential to the $K$ and $\bar{K}$ with opposite signs. This allows us to constrain the background torsion field from the $K_L$ and $K_S$ mass difference, CPT violating $K^{\circ }$ and $\overline{K^{\circ }}$ mass difference and the CP violating quantities $ϵ$ and ${\eta }_{+-}$. The most stringent bound on the cosmological background torsion $<T^0><{10}^{-25}$ GeV comes from the direct measurement of the CPT violation.