144 research outputs found
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
confidence level. T2K data and the combined data analysis excluded
standard oscillation at . 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. NOA 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 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 data is affected by \ty-hierarchy and
octant-hierarchy degeneracies, which limit the hierarchy sensitivity of such
data. A combination of and \anu data is not subject to these
degeneracies and hence has much better hierarchy discrimination capability. We
find that, with a 3 year run, hierarchy determination is possible for
only two of the four octant-hierarchy combinations. Equal 1.5 year runs in
and \anu modes give good hierarchy sensitivity for all the four
combinations
Understanding the degeneracies in NOA data
The combined analysis of disappearance and appearance data
of NOA experiment leads to three nearly degenerate solutions. This
degeneracy can be understood in terms of deviations in 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 and no CP-violation.
We then calculate the deviations induced in the appearance signal event
rate by three unknown effects: (a) matter effects, due to normal or inverted
hierarchy (b) octant effects, due to being in higher or lower
octant and (c) CP-violation, whether or . We find that the deviation caused by each of these effects is the
same for NOA. The observed number of events in NOA is
equivalent to the increase caused by one of the effects. Therefore, the
observed number of appearance events of NOA 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 NOA 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 NOA 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) disappearance, (b)
disappearance (c) appearance and (d)
appearance. There is a mild tension between the disappearance and the
appearance data sets of T2K. A more serious tension exists between the
appearance data of T2K and the appearance data of NOvA.
This tension is significant enough that T2K rules out the best-fit point of
NOvA at confidence level whereas NOvA rules out T2K best-fit point at
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 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 NOA 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 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 NOA data slightly (at
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
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 NOA and T2K 2019 data prefers the
non-unitary mixing at C.L.. We derive constraints on the
non-unitary mixing parameters using the best-fit to the combined NOA 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 C.L. The combined analysis preferes non-unitarity at 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
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