Abstract
A linearly polarized photon can be quantized from the Lorentz-boosted electromagnetic field of a nucleus traveling at ultra-relativistic speed. When two relativistic heavy nuclei pass one another at a distance of a few nuclear radii, the photon from one nucleus may interact through a virtual quark-antiquark pair with gluons from the other nucleus forming a short-lived vector meson (e.g. \({\rho^0}\)). In this experiment, the polarization was utilized in diffractive photoproduction to observe a unique spin interference pattern in the angular distribution of \({\rho^0\rightarrow\pi^+\pi^-}\) decays. The observed interference is a result of an overlap of two wave functions at a distance an order of magnitude larger than the \({\rho^0}\) travel distance within its lifetime. The strong-interaction nuclear radii were extracted from these diffractive interactions, and found to be \(6.53\pm 0.06\) fm (\(^{197} {\rm Au }\)) and \(7.29\pm 0.08\) fm (\(^{238} {\rm U}\)), larger than the nuclear charge radii. The observable is demonstrated to be sensitive to the nuclear geometry and quantum interference of non-identical particles.