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Register a new userNeutrino Oscillations at low energy long baseline experiments in the presence of nonstandard interactions and parameter degeneracy
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Osamu Yasuda
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We discuss the analytical expression of the oscillation probabilities at low energy long baseline experiments, such as T2HK and T2HKK in the presence of nonstandard interactions (NSIs). We show that these experiments are advantageous to explore the NSI parameters ($epsilon_D$, $epsilon_N$), which were suggested to be nonvanishing to account for the discrepancy between the solar neutrino and KamLAND data. We also show that, when the NSI parameters are small, parameter degeneracy in the CP phase $delta$, $epsilon_D$ and $epsilon_N$ can be resolved by combining data of the T2HK and T2HKK experiments.
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In neutrino oscillation with non-standard interactions (NSI) the system is enriched with CP violation caused by phases due to NSI in addition to the standard lepton Kobayashi-Maskawa phase delta. In this paper we show that it is possible to disentangle the two CP violating effects by measurement of muon neutrino appearance by a near-far two detector setting in neutrino factory experiments. Prior to the quantitative analysis we investigate in detail the various features of the neutrino oscillations with NSI, but under the assumption that only one of the NSI elements, epsilon_{e mu} or epsilon_{e tau}, is present. They include synergy between the near and the far detectors, the characteristic differences between the epsilon_{e mu} and epsilon_{etau} systems, and in particular, the parameter degeneracy. Finally, we use a concrete setting with the muon energy of 50 GeV and magnetized iron detectors at two baselines, one at L=3000 km and the other at L=7000 km, each having a fiducial mass of 50 kton to study the discovery potential of NSI and its CP violation effects. We demonstrate, by assuming 4 times 10^{21} useful muon decays for both polarities, that one can identify non-standard CP violation down to | epsilon_{e mu} | simeq text{a few} times 10^{-3}, and | epsilon_{e tau} | simeq 10^{-2} at 3sigma CL for theta_{13} down to sin^2 2theta_{13} = 10^{-4} in most of the region of delta. The impact of the existence of NSI on the measurement of delta and the mass hierarchy is also worked out.
In a recent work by us, we have studied, how CP violation discovery potential can be improved at long baseline neutrino experiments (LBNE/DUNE), by combining with its ND (near detector) and reactor experiments. In this work, we discuss how this study can be further analysed to resolve entanglement of the quadrant of leptonic CPV phase and Octant of atmospheric mixing angle $ theta_{23} $, at LBNEs. The study is done for both NH (Normal hierarchy) and IH (Inverted hierarchy), HO (Higher Octant) and LO (Lower Octant). We show how baryogenesis can enhance the effect of resolving this entanglement, and how possible values of the leptonic CP-violating phase $ delta_{CP} $ can be predicted in this context. With respect to the latest global fit data of neutrino mixing angles, we predict the values of $ delta_{CP} $ for different cases. In this context we present favoured values of $ delta_{CP} $ ($ delta_{CP} $ range at $ geq $ 2$ sigma $ ) constrained by the latest updated BAU range and also confront our predictions of $ delta_{CP} $ with an up-to-date global analysis of neutrino oscillation data. We find that some region of the favoured $ delta_{CP} $ parameter space lies within the best fit values around $ delta_{CP} simeq 1.3pi-1.4 pi $. A detailed analytic and numerical study of baryogenesis through leptogenesis is performed in this framework in a model independent way.
In a recent work by two of us, we have studied, how CP violation discovery potential can be improved at long baseline neutrino experiments (LBNE/DUNE), by combining with its ND (near detector) and reactor experiments. In this work, we discuss how this study can be further analyzed to resolve entanglement of the quadrant of leptonic CPV phase and Octant of atmospheric mixing angle $theta_{23}$, at LBNEs. The study is done for both NH (Normal hierarchy) and IH (Inverted hierarchy), HO (Higher Octant) and LO (Lower Octant). We show how leptogenesis can enhance the effect of resolving this entanglement, and how possible values of the leptonic CPV phase can be predicted in this context. Carrying out numerical analysis based on the recent updated experimental results for neutrino mixing angles, we predict the values of the leptonic CPV phase for 152 possible cases. We also confront our predictions of the leptonic CPV phase with the updated global fit and find that five values of $delta_{CP}$ are favoured by BAU constraints. One of the five values matches with the recent global fit value of $delta_{CP}$ (leptonic CPV phase) close to 1.41 $pi$ in our model independent scenario. A detailed analytic and numerical study of baryogenesis through leptogenesis is performed in this framework in a model independent way.
The results obtained by several experiments on atmospheric neutrino oscillations are summarized and discussed. Then the results obtained by different long baseline neutrino experiments are considered. Finally conclusions and perspectives are made.
We formulate an Effective Field Theory (EFT) for Non Standard neutrino Interactions (NSI) in elastic scattering with light quarks, leptons, gluons and photons, including all possible operators of dimension 5, 6 and 7. We provide the expressions for the cross sections in coherent neutrino-nucleus scattering and in deep inelastic scattering. Assuming single operator dominance we constrain the respective Wilson coefficient using the measurements by the COHERENT and CHARM collaborations. We also point out the constraining power of future elastic neutrino-nucleus scattering experiments. Finally, we explore the implications of the bounds for SMEFT operators above the electroweak breaking scale.
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