Looking for Lorentz invariance violation (LIV) in the latest long baseline accelerator neutrino oscillation data

In this paper, we have analysed the latest data from \nova and T2K with the Lorentz invariance violation along with the standard oscillation hypothesis. We have found that the \nova data cannot distinguish between the two hypotheses at $1\, \sigma$ confidence level. T2K data and the combined data analysis excluded standard oscillation at $1\, \sigma$. All three cases do not have any hierarchy sensitivity when analysed with LIV. There is a mild tension between the two experiments, when analysed with LIV, as \tz at \nova best-fit is at higher octant but the same for T2K is at lower octant. NO$\nu$A has a new degeneracy over \sin^2 \tz value, when analysed with LIV.Comment: 16 pages, 5 figure

The need for an early anti-neutrino run of NOvA

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 $\nu$ 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 higher octant. Pure $\nu$ data is affected by \ty-hierarchy and octant-hierarchy degeneracies, which limit the hierarchy sensitivity of such data. A combination of $\nu$ and \anu data is not subject to these degeneracies and hence has much better hierarchy discrimination capability. We find that, with a 3 year $\nu$ run, hierarchy determination is possible for only two of the four octant-hierarchy combinations. Equal 1.5 year runs in $\nu$ and \anu modes give good hierarchy sensitivity for all the four combinations

Understanding the degeneracies in NOν\nuA data

The combined analysis of $\nu_\mu$ disappearance and $\nu_e$ appearance data of NO$\nu$A experiment leads to three nearly degenerate solutions. This degeneracy can be understood in terms of deviations in $\nu_e$ appearance signal, caused by unknown effects, with respect to the signal expected for a reference set of oscillations parameters. We define the reference set to be vacuum oscillations in the limit of maximal $\theta_{23}$ and no CP-violation. We then calculate the deviations induced in the $\nu_e$ appearance signal event rate by three unknown effects: (a) matter effects, due to normal or inverted hierarchy (b) octant effects, due to $\theta_{23}$ being in higher or lower octant and (c) CP-violation, whether $\delta_{CP} \sim - \pi/2$ or $\delta_{CP} \sim \pi/2$. We find that the deviation caused by each of these effects is the same for NO$\nu$A. The observed number of $\nu_e$ events in NO$\nu$A is equivalent to the increase caused by one of the effects. Therefore, the observed number of $\nu_e$ appearance events of NO$\nu$A is the net result of the increase caused by two of the unknown effects and the decrease caused by the third. Thus we get the three degenerate solutions. We also find that further data by NO$\nu$A can not distinguish between these degenerate solutions but addition of one year of neutrino run of DUNE can make a distinction between all three solutions. The distinction between the two NH solutions and the IH solution becomes possible because of the larger matter effect in DUNE. The distinction between the two NH solutions with different octants is a result of the synergy between the anti-neutrino data of NO$\nu$A and the neutrino data of DUNE.Comment: Published version v2; with minor changes to v

Tensions between the appearance data of T2K and NOvA

The long baseline neutrino experiments, T2K and NOvA, have taken significant amount of data in each of the four channels: (a) $\nu_\mu$ disappearance, (b) $\bar\nu_\mu$ disappearance (c) $\nu_e$ appearance and (d) $\bar\nu_e$ appearance. There is a mild tension between the disappearance and the appearance data sets of T2K. A more serious tension exists between the $\nu_e$ appearance data of T2K and the $\nu_e / \bar\nu_e$ appearance data of NOvA. This tension is significant enough that T2K rules out the best-fit point of NOvA at $95\%$ confidence level whereas NOvA rules out T2K best-fit point at $90\%$ confidence level. We explain the reason why these tensions arise. We also do a combined fit of T2K and NOvA data and comment on the results of this fit.Comment: matches the published versio

Effect of non-unitary mixing on the mass hierarchy and CP violation determination at the Protvino to Orca experiment

In this paper, we have estimated the neutrino mass ordering and the CP violation sensitivity of the proposed Protvino to Orca (P2O) experiment after 6 years of data-taking. Both unitary and non-unitary $3\times 3$ neutrino mass mixing have been considered in the simulations. A forecast analysis deriving possible future constraints on non-unitary parameters at P2O have been performed.Comment: 26 pages, 18 figures, 2 table

Searching for non-unitary neutrino oscillations in the present T2K and NOν\nuA data

The mixing of three active neutrino flavors is parameterized by the unitary PMNS matrix. If there are more than three neutrino flavors and if the extra generations are heavy isosinglets, the effective $3\times 3$ mixing matrix for the three active neutrinos will be non-unitary. We have analyzed the latest T2K and \nova data with the hypothesis of non-unitary mixing of the active neutrinos. We found that the 2019 NO$\nu$A data slightly (at $\sim 1\, \sigma$ C.L.) prefer the non-unitary mixing over unitary mixing. In fact, allowing the non-unitary mixing brings the \nova best-fit point in the $\sin^2\theta_{23}-\delta_{CP}$ plane closer to the T2K best-fit point. The 2019 T2K data, on the other hand, cannot rule out any of the two mixing schemes. A combined analysis of the NO$\nu$A and T2K 2019 data prefers the non-unitary mixing at $1\, \sigma$ C.L.. We derive constraints on the non-unitary mixing parameters using the best-fit to the combined NO$\nu$A and T2K data. These constraints are weaker than previously found. The latest 2020 data from both the experiments prefer non-unitarity over unitary mixing at $1\, \sigma$ C.L. The combined analysis preferes non-unitarity at $2\, \sigma$ C.L. The stronger tension, which exists between the latest 2020 data of the two experiments, also gets reduced with non-unitary analysis.Comment: 30 pages, 19 figures, 3 tables. Results for 2020 data from NOvA and T2K have been include