Quantum Interferometry in $ρ^0$ Production in Ultra-Peripheral Heavy Ion Collisions

Abstract

In $ρ^0$ photoproduction in ultra-peripheral heavy ion collisions, either ion can be the photon emitter or the target. The two possibilities are indistinguishable, and they should be able to interfere, reducing $rho^0$ production at low transverse momentum, $p_T<\hbar/< b>$, where $ $ is the median impact parameter. The two $ρ^0$ production points are separated by $ \approx 18-46$ fm, while the $ρ^0$ decay before travelling 1 fm. The two decay points are well separated in space-time, so the decays proceed independently and any interference must involve the final state $π^+π^-$. This requires a non-local wave function.