Matter vs vacuum oscillations in atmospheric neutrinos

At present, both vacuum oscillations as well as matter modified oscillations can explain the data of atmospheric neutrino experiments and the long baseline accelerator neutrino experiments equally well. Given the important role the matter effects play in the determination of CP violation in neutrino oscillations, it is imperative to establish the signal for matter effects unambiguously. In this work, we study the ability of ICAL at INO to make a distinction between vacuum oscillations and matter modified oscillations. We find that it is possible to make a 3σ discrimination in ten years, whether the atmospheric mass-squared difference is positive or negative.