According to the recent results of the neutrino oscillation experiment MINOS, the neutrino mixing angle $θ_{23}$ may not be maximal ($45^{\circ}$). Two nearly degenerate solutions are possible, one in the lower octant (LO) where $θ_{23}<45^{\circ}$, and one in the higher octant (HO) where $θ_{23}>45^{\circ}$. Long baseline experiments measuring the $ν_μ\rightarrowν_{e}$ are capable of resolving this degeneracy. In this work we study the potential of the planned European LBNO experiment to distinguish between the LO and HO solutions.
Determination of the neutrino mass hierarchy, octant of the mixing angle theta_{23} and the CP violating phase delta_{CP} are the unsolved problems in neutrino oscillation physics today. In this paper our aim is to obtain the minimum exposure required for the proposed Long Baseline Neutrino Oscillation (LBNO) experiment to determine the above unknowns. We emphasize on the advantage of exploiting the synergies offered by the existing and upcoming long-baseline and atmospheric neutrino experiments in economising the LBNO configuration. In particular, we do a combined analysis for LBNO, T2K, NOvA…
Long baseline Experiment (LBL) have promised to be a very powerful experimental set up to study various issues related to Neutrinos. Some ongoing and planned LBL and medium baseline experiments are - T2K, MINOS, NOvA, LBNE, LBNO etc. But the long baseline experiments are crippled due to presence of some parameter degeneracies, like the Octant degeneracy. In this work, we first show the presence of Octant degeneracy in LBL experiments, and then combine it with Daya Bay Reactor experiment, at different values of CP violation phase. We show that the Octant degeneracy in LBNE can be resolved compl…
The recent discovery by the Daya-Bay and RENO experiments, that θ_{13} is nonzero and relatively large, significantly impacts existing experiments and the planning of future facilities. In many scenarios, the nonzero value of θ_{13} implies that θ_{23} is likely to be different from π/4. Additionally, large detectors will be sensitive to matter effects on the oscillations of atmospheric neutrinos, making it possible to determine the neutrino mass hierarchy and the octant of θ_{23}. We show that a 50 kT magnetized liquid argon neutrino detector can ascertain the mass hierarchy with a significan…
The recent data indicate that the neutrino mixing angle $θ_{23}$ deviates from the maximal-mixing value of 45$^\circ$, showing two nearly degenerate solutions, one in the lower octant (LO) ($θ_{23}<45^\circ$) and one in the higher octant (HO) ($θ_{23}>45^\circ$). We investigate, using numerical simulations, the prospects for determining the octant of $θ_{23}$ in the future long baseline oscillation experiments. We present our results as contour plots on the ($θ_{23}-45^\circ$, $δ$)--plane, where $δ$ is the $CP$ phase, showing the true values of $θ_{23}$ for which the octant can be experimental…
The octant of $θ_{23}$ and $δ_{CP}$ are the two major unknowns in neutrino oscillation physics. The precise determination of octant and $δ_{CP}$ is interlinked through the octant-$δ_{CP}$ degeneracy. In this paper we study the proficiency of the DUNE experiment to determine these parameters, in particular, the role played by the antineutrinos, the broadband nature of the beam and the matter effect. For $P_{μe}$ and $P_{\barμ \bar{e}}$ the octant-$δ_{CP}$ degeneracy occurs at different values of $δ_{CP}$, combination of neutrino and antineutrino runs help to resolve this. However, in regions wh…
We investigate the prospects for determining the octant of $θ_{23}$ in the future long baseline oscillation experiments. We present our results as contour plots on the ($θ_{23}-45^\circ$, $δ$)--plane, where $δ$ is the CP phase, showing the true values of $θ_{23}$ for which the octant can be experimentally determined at 3$\,σ$, 2$\,σ$ and 1$\,σ$ confidence level, in particular, the impact of the non-unitarity of neutrino mixing.
Preliminary results of MINOS experiment indicate that theta23 is not maximal. Global fits to world neutrino data suggest two nearly degenerate solutions for theta23: one in the lower octant (LO: theta23 < 45 degree) and the other in the higher octant (HO: theta23 > 45 degree). numu to nue oscillations in superbeam experiments are sensitive to the octant and are capable of resolving this degeneracy. We study the prospects of this resolution by the current T2K and upcoming NOvA experiments. Because of the hierarchy-deltacp degeneracy and the octant-deltacp degeneracy, the impact of hierarchy on …
We expound in detail the degeneracy between the octant of $θ_{23}$ and flavor-changing neutral-current non-standard interactions (NSI's) in neutrino propagation, considering the Deep Underground Neutrino Experiment (DUNE) as a case study. In the presence of such NSI parameters involving the $e-μ$ ($\varepsilon_{eμ}$) and $e-τ$ ($\varepsilon_{eτ}$) flavors, the $ν_μ\to ν_e$ and $\barν_μ\to \barν_e$ appearance probabilities in long-baseline experiments acquire an additional interference term, which depends on one new dynamical CP-phase $ϕ_{eμ/eτ}$. This term sums up with the well-known interfere…
We examine accuracy of theta_{23} determination in future long-baseline (LBL) nu_{mu} disappearance experiments in the three-flavor mixing scheme of neutrinos. Despite that the error of sin^2{2theta_{23}} is indeed a few % level at around the maximal mixing, we show that the error of physics variable s^2_{23} is large, delta(s^2_{23})/s^2_{23} \simeq 10-20%, depending upon regions of theta_{23}. The errors are severely affected by the octant degeneracy of theta_{23}, and delta(s^2_{23}) is largely amplified by the Jacobian factor relating these two variables in a region near to the maximal mix…
We explore the prospects of determining the octant of $θ_{23}$ with atmospheric neutrinos at PINGU. We study in detail the impact of energy and angle resolutions of the neutrino on the octant sensitivity. We show that the systematic uncertainties on the atmospheric neutrino flux predictions, especially the ones which affect the energy and zenith angle spectrum of the neutrinos, make a rather drastic reduction of the sensitivity of PINGU. We also study the prospects of measuring the octant of $θ_{23}$ in the long baseline experiments T2K and NOvA in conjunction with the reactor experiments. We …
We study parameter degeneracies that can occur in long-baseline neutrino appearance experiments due to nonstandard interactions (NSI) in neutrino propagation. For a single off-diagonal NSI parameter, and neutrino and antineutrino measurements at a single L/E, there exists a continuous four-fold degeneracy (related to the mass hierarchy and $θ_{23}$ octant) that renders the mass hierarchy, octant, and CP phase unknowable. Even with a combination of NO$ν$A and T2K data, which in principle can resolve the degeneracy, both NSI and the CP phase remain unconstrained because of experimental uncertain…
We present the results of a global analysis of the neutrino oscillation data available as of fall 2018 in the framework of three massive mixed neutrinos with the goal at determining the ranges of allowed values for the six relevant parameters. We describe the complementarity and quantify the tensions among the results of the different data samples contributing to the determination of each parameter. We also show how those vary when combining our global likelihood with the chi^2 map provided by Super-Kamiokande for their atmospheric neutrino data analysis in the same framework. The best fit of …
At present the three major unknowns in neutrino oscillation parameters are the mass hierarchy, the octant of $θ_{23}$ and the CP phase $δ_{CP}$. It is well known that the presence of hierarchy$-δ_{CP}$ and octant degeneracies affects the unambiguous determination of these parameters. In this paper we show that a comprehensive way to study the remaining parameter degeneracies is in the form of a generalized hierarchy-$θ_{23}$ - $δ_{CP}$ degeneracy. We show that the wrong-hierarchy and/or wrong-octant solutions can be further classified into eight different solutions depending on whether they oc…
Recent measurements of large theta_{13} by Daya Bay and RENO reactor experiments have opened up the possibility of determining the neutrino mass hierarchy, i.e. the sign of the mass squared splitting Delta m_{31}^2, the CP-violating phase delta_{CP} and the octant of theta_{23}. In the light of this result, we study the performance of a low energy neutrino factory (LENF) for determination of the mass hierarchy. In particular, we explore the potential of the nu_e$ and barν_e disappearance channels at LENF to determine the neutrino mass hierarchy, that is free from the uncertainties arising from…
Using the latest global determination of neutrino oscillation parameters from~\cite{deSalas:2017kay} we examine the status of the simplest revamped version of the BMV (Babu-Ma-Valle) model, proposed in~\cite{Morisi:2013qna}. The model predicts a striking correlation between the "poorly determined" atmospheric angle $θ_{23}$ and CP phase $δ_{CP}$, leading to either maximal CP violation or none, depending on the preferred $θ_{23}$ octants. We determine the allowed BMV parameter regions and compare with the general three-neutrino oscillation scenario. We show that in the BMV model the higher octa…
We present an up-to-date global analysis of solar, atmospheric, reactor, and accelerator neutrino data in the framework of three-neutrino oscillations. We provide results on the determination of theta_13 from global data and discuss the dependence on the choice of reactor fluxes. We study in detail the statistical significance of a possible deviation of theta_23 from maximal mixing, the determination of its octant, the ordering of the mass states, and the sensitivity to the CP violating phase, and discuss the role of various complementary data sets in those respects.
A high-power neutrino superbeam experiment at the ESS facility has been proposed such that the source-detector distance falls at the second oscillation maximum, giving very good sensitivity towards establishing CP violation. In this work, we explore the comparative physics reach of the experiment in terms of leptonic CP-violation, precision on atmospheric parameters, non-maximal theta23, and its octant for a variety of choices for the baselines. We also vary the neutrino vs. the anti-neutrino running time for the beam, and study its impact on the physics goals of the experiment. We find that f…
The moderately large value of $\ty$, measured recently by reactor experiments, is very welcome news for the future neutrino experiments. In particular, the \nova experiment, with 3 years each of $ν$ and $\anu$ runs, will be able to determine the mass hierarchy if one of the following two favourable combinations is true: normal hierarchy with $-180^\circ \leq \dcp \leq 0$ or inverted hierarchy with $0\leq \dcp \leq 180^\circ$. In this report, we study the hierarchy reach of the first 3 years of \nova data. Since $\sin^2 2 \tz$ is measured to be non-maximal, $\tz$ can be either in the lower or h…
In this paper, we perform a comparative analysis between the future proposed long-baseline experiments ESSnuSB and T2HK in measuring the leptonic CP phase $δ_{\rm CP}$. In particular, we study the effect of the neutrino mass ordering degeneracy and the leptonic mixing angle $θ_{23}$ octant degeneracy in the measurement of leptonic CP violation and precision for both experiments. Since the ESSnuSB (T2HK) experiment probes the second (first) oscillation maximum to study neutrino oscillations, the effect of these degeneracies are significantly different in both experiments. Our main conclusion is…
Non-standard neutrino interactions (NSIs), the sub-leading effects in the flavour transitions of neutrinos, play a crucial role in the determination of the various unknowns in neutrino oscillations, such as neutrino mass hierarchy, Dirac CP violating phase and the octant of atmospheric mixing angle. In this work, we focus on the possible implications of lepton flavour violating (LFV) NSIs, which generally affect the neutrino propagation, on the determination of the these unknown oscillation parameters. We study the effect of these NSIs on the physics potential of the currently running and upco…
The Deep Underground Neutrino Experiment (DUNE) is a leading experiment in neutrino physics which is presently under construction. DUNE aims to measure the yet unknown parameters in the three flavour oscillation scenario which includes discovery of leptonic CP violation, determination of the mass hierarchy and determination of the octant of $θ_{23}$. Additionally, the ancillary goals of DUNE include probing the sub-dominant effects induced by new physics. A widely studied new physics scenario is that of nonstandard neutrino interactions (NSI) in propagation which impacts the oscillations of ne…
Recent global fit analyses of oscillation data show a preference for normal mass ordering (NMO) at 2.5$σ$ and provide 1.6$σ$ indications for lower $θ_{23}$ octant and leptonic CP violation. A high-precision measurement of $θ_{23}$ is pivotal to convert these hints into discoveries. In this work, we study in detail the capabilities of DUNE to establish the deviation from maximal $θ_{23}$ and to resolve its octant at high confidence levels. We exhibit the possible correlations and degeneracies among $\sin^2θ_{23}$, $Δm^2_{31}$, and $δ_{CP}$ in disappearance and appearance oscillation channels at…
Precision measurement of the neutrino mixing parameters and the determination of mass hierarchy are the primary goals of the present and upcoming neutrino experiments. In this work, we study the sensitivity of T2K,NO$ν$A and LBNE experiments to discover leptonic CP violation and the determination of neutrino mass hierarchy. We obtain the correlation between the CP violating phase $δ_{CP}$ and the mixing angles $θ_{13}$, $θ_{23}$ and the sensitivity to determine the octant of atmospheric mixing angle $θ_{23}$. The entire analysis is done for a total 10 years (5$ν$+ 5$\bar ν$) of running of T2K,…
The recent results of the Planck experiment put a stringent constraint on the sum of the light neutrino masses, m1+m2+m3 < 0.23 eV (95 % CL). On the other hand, two-zero Majorana mass matrix textures predict strong correlations among the atmospheric angle and the sum of the masses. We use the Planck result to show that, for the normal hierarchy case, the texture with vanishing (2,2) and (3,3) elements is ruled out at a high confidence level; in addition, we emphasize that a future measurement of the octant of the atmospheric mixing angle (or the one sigma determination of it based on recent fi…
The NuMI Off-Axis $ν_{e}$ Appearance (NO$ν$A) is the currently running leading long-baseline neutrino oscillation experiment, whose main physics goal is to explore the current issues in the neutrino sector, such as determination of the neutrino mass ordering, resolution of the octant of atmospheric mixing angle and to constrain the Dirac-type CP violating phase $δ_{CP}$. In this paper, we would like to investigate whether it is possible to extract the best possible results from NO$ν$A with a shorter time-span than its scheduled run period by analyzing its capability to discriminate the degener…
We confront recent experimental results on neutrino mixing parameters with the requirements from strong thermal $SO(10)$-inspired leptogenesis, where the asymmetry is produced from next-to-lightest right-handed neutrinos $N_2$ independently of the initial conditions. There is a nice agreement with latest global analyses supporting $\sinδ< 0$ and normal ordering at $ \sim 95\%$ C.L. On the other hand, the more stringent experimental lower bound on the atmospheric mixing angle starts to corner strong thermal $SO(10)$-inspired leptogenesis. Prompted and encouraged by this rapid experimental advan…
