Measuring tau neutrino appearance probability via unitarity

Abstract

We propose a unitarity method for determining τ neutrino appearance probability P (ν µ → ν τ ) in long-baseline (LBL) accelerator experiments and atmospheric neutrino observations. When simultaneous in situ measurements of P (ν µ → ν µ ) and P (ν µ → ν e ) proceed, as is typical in the LBL experiments, one can use unitarity to "measure" P (ν µ → ν τ ). A theorists' toy analysis for the model-independent determination of P (ν µ → ν µ ) and P (ν µ → ν e ) is presented by using the NOvA data. It is shown in our analysis that < ∼ 5% (8%) measurement of τ neutrino appearance probability in neutrino (antineutrino) mode is possible in the peak region 1.5 < ∼ E ν < ∼ 2.5 GeV. The νSM-independent nature of determination of the probabilities is emphasized.

Model-Independent Constraints on Non-Unitary Neutrino Mixing from High-Precision Long-Baseline Experiments

“…However, the DUNE neutrino spectra will have peak at around 2.5 GeV (differently from the T2HKK where E ν 0.6 GeV) and the most energetic neutrinos of the beam will have enough energy to produce τ leptons. Recently, different studies [50,[84][85][86] take into account the possibility of including the ν τ (ν τ ) sample in the DUNE analysis. The recognition of such events could be in principle possible due to the imaging capabilities of LArTPC detectors.…”