  The W boson can obtain a small right-handed coupling to quarks and leptons
through mixing with a hypothetical W' boson that appears in many extensions of
the Standard Model. Measuring or even bounding this coupling to the light
quarks is very challenging. Only one model independent bound on the absolute
value of the complex mixing parameter has been obtained to date. Here we
discuss a method sensitive to both the real and CP-violating imaginary parts of
the coupling, independent of assumptions on the new physics, and demonstrate
quantitatively the feasibility of its measurement at RHIC.
