Constraining CPT violation with Hyper-Kamiokande and ESSnuSB

Charge conjugation, Parity and Time reversal together (CPT) is the fundamental symmetry of the nature. If the CPT symmetry is violated, it will be a great threat to all the well explained theories. Although no definitive signal of CPT violation has been observed so far, there are many reasons to undertake careful investigation of various low-energy phenomena which can at least provide some stringent limits on CPT violation. In this regard, neutrinos are considered to be one of the most accurate tools to test this symmetry. In this work, we therefore investigate the effect of CPT violation through neutrino oscillations. If we assume the fundamental CPT symmetry to be conserved, both neutrino and antineutrino oscillations can be parametrised using the same set of oscillation parameters. Any small deviation to the neutrino properties during their propagation due to CPT violation, can be studied explicitly in long-baseline experiments. We discuss the potential of various long-baseline experiments to impart the bounds on the CPT violating parameters: $\Delta(\delta_{CP})$, $\Delta(m^2_{31})$ and $\Delta(\sin^2 \theta_{23})$, which characterize the difference between neutrino and antineutrino oscillation parameters.