Measuring the leptonic CP phase δCP and resolving the θ23 octant are primary objectives of DUNE and T2HK. We show that two distinct effects can compromise the reliability of these measurements. First, the poorly constrained νe and νμ cross sections allow energy-dependent distortions that partially mimic the δCP-dependent spectral modulation, reducing DUNE's CP-violation sensitivity by up to 3σ. We demonstrate that the proposed nuSCOPE facility at CERN can recover this loss through percent-level measurements of σνe and the σνe/σνμ ratio. Second, complex non-standard interactions (NSI) in propagation, motivated by the current 2σ NOvA-T2K tension, induce correlated biases in δCP and the θ23 octant when DUNE data are interpreted under the standard three-flavor hypothesis. Since T2HK is largely insensitive to these propagation effects, a 3σ discrepancy between the two experiments would constitute a clear diagnostic of BSM physics. These results highlight that both external cross-section constraints and baseline complementarity are essential to ensure a robust and unbiased determination of the oscillation parameters in the precision era.
Joao Paulo Pinheiro, Postdoctoral Scholar, Tsung-Dao Lee Institute, Shanghai
Host: Gustavo Alves
Joan West
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