Hierarchy Independent sensitivity to the octant with ORCA115 N. R. - - PowerPoint PPT Presentation

Hierarchy Independent sensitivity to the octant with ORCA115

• N. R. Khan Chowdhury

14 Jan. 2020 | N. R. Khan Chowdhury | ORCA Phone Call |

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Octant degeneracy

The ambiguity in the determination of 𝜾23 can be from two sources, 1) Inherent octant degeneracy: Oscillation and survival probabilities are function of sin22𝜾23. 2) Degeneracy of the octant with other oscillation parameters: oscillation and survival probabilities are function of sin2𝜾23 or cos2𝜾23. Probabilities become identical for value of 𝜾23 in opposite octant for different value of 𝜾13 and 𝜺CP.

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Octant ambiguity ensued in P𝝂e and Pee

The relevant probabilities in the OMSD approximation with matter effects reads During matter resonance, sin2𝜾13

m reaches value of 1 irrespective of the value of 𝜾13 in vacuum and the

product is no longer invariant for opposite octants for different values of 𝜾13. The electron survival probability is independent of 𝜾23 and does not contribute to octant sensitivity.

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P𝝂e in light of non-zero 𝜾13

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For 𝜾23 in lower octant (solid line), higher values of 𝜾13 (~8.9°) can give a higher octant sensitivity since the solid line is more separated from the wrong 𝜾23 band (dashed lines) of variation of the probability over the whole range of test 𝜾13. The reverse is true for 𝜾23 in HO.

Octant ambiguity ensued in P𝝂𝝂

The strong octant sensitive behaviour of sin4𝜾23sin22𝜾13

m near resonance can override the degeneracy

since 𝜾13 in matter gets amplified to maximal values.

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Leading terms (octant degenerate) sub-leading term lifting the degeneracy

P𝝂𝝂 in light of non-zero 𝜾13

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The effect of 𝜾13 on the separation between opposite bands is less, since the dominated by intrinsic octant degeneracy. Yet, for 𝜾23 in lower octant (solid line), lower values of 𝜾13 (~8.1°) can give a higher octant sensitivity since the solid line is more separated from the wrong 𝜾23 band (dashed lines). The reverse is true for 𝜾23 in HO.

Asymmetry in P𝝂𝝂 and P𝝂e channel

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Normal Ordering, 𝜾13 = 8.54° (NuFit3.2)

Octant Sensitivity: True NO

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In both cases, the min chisq is never reached in the wrong hierarchy. This confirms, NMO is not an issue in the octant determination at ORCA. The 𝛙2 is lower for true HO in general. 𝛙2 = (NLO(HO) - NHO(LO))2 / NHO(LO) for true HO (LO). Although the numerator remains the same, the denominator is larger for true HO resulting in lower sensitivity. T2K (4+4) + NO𝝃A (3+3)

Octant Sensitivity: True IO

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In both cases, the min chisq is never reached in the wrong hierarchy. This confirms, NMO is not an issue in the octant determination at ORCA. Assuming Inverted Ordering gives worse results since, matter resonance and hence octant sensitivity comes from the anti-neutrino channel for which flux and cross-sections are lower.

Octant Sensitivity:

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T2K (3 years neutrino mode) + NO𝝃A (3+3).

Summary:

1) Preliminary estimation of octant sensitivity has been studied with ORCA115. 2) Neutrino mass ordering is not a source of ambiguity in the octant determination at ORCA. 3) Study octant sensitivity in the presence of NSI/Steriles is foreseen in the future.

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THANKS