Propagation of scintillation light in Liquid Argon

The properties of the propagation of scintillations light in the liquid argon, at λ=128 nm wavelength, has been experimentally investigated in a dedicated setup at CERN. The velocity of scintillation photons has been measured for the first time in the liquid argon. The obtained result, 1/vg = 7.5 ± 0.1 ns/m, is then used to derive the refractive index and the Rayleigh scattering of the liquid argon at VUV region. Such measurement provides a key ingredient for the interpretation of data from the current and next generation large mass liquid argon detectors as those dedicated to the search for rare events such as neutrinos or Dark Matter. Furthermore the improvement on the understanding of the scintillation light propagation represent a benchmark for the multiple theoretical models and simulations for the next generation of detectors.