• Sushant K Raut

      Articles written in Pramana – Journal of Physics

    • Evidence for leptonic CP phase from NO𝜈A, T2K and ICAL

      Monojit Ghosh Pomita Ghoshal Srubabati Goswami Sushant K Raut

      More Details Abstract Fulltext PDF

      The phenomenon of neutrino oscillation is now well understood from the solar, atmospheric, reactor and accelerator neutrino experiments. This oscillation is characterized by a unitary PMNS matrix which is parametrized by three mixing angles (𝜃12, 𝜃23 and 𝜃13) and one phase (𝛿CP) known as the leptonic CP phase. Neutrino oscillation also involves two mass squared differences: the solar mass square difference (𝛥21 = 𝑚22 − 𝑚21) and the atmospheric mass square difference (𝛥31 = |𝑚23−𝑚21|). Though there is already significant amount of information about the three mixing angles, the CP phase is still unknown. Apart from the CP phase, one should also know what is the true nature of the neutrino mass hierarchy, i.e., normal (𝑚3 > 𝑚1: NH) or inverted (𝑚1 > 𝑚3: IH) and what is the true octant of 𝜃23, i.e., lower (𝜃23 < 45°: LO) or higher (𝜃23 > 45°: HO). The long-baseline experiments (LBL) have CP sensitivity coming from the appearance channel $(\nu_{\mu} \rightarrow \nu_{e}$). On the other hand, atmospheric neutrinos are known to have negligible CP sensitivity. In this work, we study the synergy between the LBL experiment NO𝜈A, T2K and the atmospheric neutrino experiment ICAL@INO for obtaining the first hint of CP violation in the lepton sector. We find that due to the lack of knowledge of hierarchy and octant, CP sensitivity of NO𝜈A/T2K is poorer for some parameter ranges. Addition of ICAL data to T2K and NO𝜈A can exclude these spurious wrong-hierarchy and/or wrong-octant solutions and cause a significant increase in the range of 𝛿CP values for which a hint of CP violation can be achieved. Similarly, the precision with which 𝛿CP can be measured also improves with the inclusion of ICAL data.

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