Probing CP Violation with Neutrino Disappearance Alone

The best way to probe CP violation in the lepton sector is with long-baseline accelerator neutrino experiments in the appearance mode: the appearance of nu e e in predominantly nu mu mu beams. Here we show that it is possible to discover CP violation with disappearance experiments only, by combining JUNO for electron neutrinos and DUNE or Hyper-Kamiokande for muon neutrinos. While the maximum sensitivity to discover CP is quite modest (1.6 sigma with 6 years of JUNO and 13 years of DUNE), some values of delta may be disfavored by > 3 sigma depending on the true value of delta.