Experimental Limit on the Proton Electric Dipole Moment

A high-precision molecular-beam-resonance experiment has been carried out to look for a violation of $P$ and $T$ invariances in a molecule. The null result can be interpreted in terms of the electric dipole moment of the proton to give $\left|d_p\right|=(7\mathrm{}\pm 9)\times {10}^{-21\mathrm{}}$ e cm.