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Register a new userOctant Degeneracy, Quadrant of CPV phase at Long Baseline $ u$ Experiments and Baryogenesis
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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.
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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.
We study the possibility of determining the octant of the neutrino mixing angle $theta_{23}$, that is, whether $theta_{23}> 45^circ$ or $theta_{23}<45^circ$, in long baseline neutrino experiments. Here we numerically derived the sensitivity limits within which these experiments can determine, by measuring the probability of the $ u_{mu}to u_{e}$ transitions, the octant of $theta_{23}$ with a $5sigma$ certainty. The interference of the CP violation angle $delta$ with these limits, as well as the effects of the baseline length and the run-time ratio of neutrino and antineutrino modes of the beam have been analyzed.
One of the unknown parameters in neutrino oscillations is the octant of the mixing angle theta_{23}. In this paper, we discuss the possibility of determining the octant of theta_{23} in the long baseline experiments T2K and NOvA in conjunction with future atmospheric neutrino detectors, in light of non-zero value of theta_{13} measured by reactor experiments. We consider two detector technologies for atmospheric neutrinos - magnetized iron calorimeter and non-magnetized Liquid Argon Time Projection Chamber. We present the octant sensitivity for T2K/NOvA and atmospheric neutrino experiments separately as well as combined. For the long baseline experiments, a precise measurement of theta_{13}, which can exclude degenerate solutions in the wrong octant, increases the sensitivity drastically. For theta_{23} = 39^o and sin^2 2 theta_{13} = 0.1, at least ~2 sigma sensitivity can be achieved by T2K+NOvA for all values of delta_{CP} for both normal and inverted hierarchy. For atmospheric neutrinos, the moderately large value of theta_{13} measured in the reactor experiments is conducive to octant sensitivity because of enhanced matter effects. A magnetized iron detector can give a 2 sigma octant sensitivity for 500 kT yr exposure for theta_{23} = 39^o, delta_{CP} = 0 and normal hierarchy. This increases to 3 sigma for both hierarchies by combining with T2K+NOvA. This is due to a preference of different theta_{23} values at the minimum chi^2 by T2K/NOvA and atmospheric neutrino experiments. A Liquid Argon detector for atmospheric neutrinos with the same exposure can give higher octant sensitivity, due to the interplay of muon and electron contributions and superior resolutions. We obtain a ~3 sigma sensitivity for theta_{23} = 39^o for normal hierarchy. This increases to > ~4 sigma for all values of delta_{CP} if combined with T2K+NOvA. For inverted hierarchy the combined sensitivity is ~3 sigma.
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.
The recent data indicate that the neutrino mixing angle $theta_{23}$ deviates from the maximal-mixing value of 45$^circ$, showing two nearly degenerate solutions, one in the lower octant (LO) ($theta_{23}<45^circ$) and one in the higher octant (HO) ($theta_{23}>45^circ$). We investigate, using numerical simulations, the prospects for determining the octant of $theta_{23}$ in the future long baseline oscillation experiments. We present our results as contour plots on the ($theta_{23}-45^circ$, $delta$)--plane, where $delta$ is the $CP$ phase, showing the true values of $theta_{23}$ for which the octant can be experimentally determined at 3$,sigma$, 2$,sigma$ and 1$,sigma$ confidence level. In particular, we study the impact of the possible nonunitarity of neutrino mixing on the experimental determination of $theta_{23}$ in those experiments.
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