Octant Sensitivity with KM3NeT-ORCA N. R. Khan Chowdhury 1 14 Jan. - - PowerPoint PPT Presentation

Octant Sensitivity with KM3NeT-ORCA

• N. R. Khan Chowdhury

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

1

What is 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.

Conventions: Lower (Higher) Octant => LO (HO). Normal (Inverted) Ordering => NO (IO).

2

Octant ambiguity in the electron channels

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

m reaches value ~ 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.

3

P𝝂e in light of non-zero 𝜾13

4

Figure depicts the separation of LO and HO curves for three different true 𝜾13 values. NO assumed. For 𝜾23 in LO (= 42.8° in plots), lower values of true 𝜾13 (left) is imperative to get higher sensitivity to the

• ctant resolution since it is more separated from the wrong 𝜾23 lines of variation of the probability over the

whole range of test 𝜾13. As the true 𝜾13 increases, the separation decreases. The reverse is true for 𝜾23 in HO.

Octant ambiguity ensued in muon channels

The strong octant sensitive behaviour of sin4𝜾23sin22𝜾13

m near resonance can override the degeneracy

since 𝜾13 in matter gets amplified to maximal values. Since Pe𝝂 is the CP conjugate of P𝝂e, the probability level discussion is the same as P𝝂e for no CPV assumptions.

5

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

P𝝂𝝂 in light of non-zero 𝜾13

6

Figure depicts the separation of LO and HO curves for three different true 𝜾13 values. NO assumed. The effect of 𝜾13 on the separation between opposite 𝜾23 lines is less, since it is governed by intrinsic octant degeneracy. Still, for 𝜾23 in LO (= 42.8° in plots) higher values of 𝜾13 (right) can give a higher octant sensitivity since it is more separated from the wrong 𝜾23 lines varied over entire range of 𝜾13. The reverse is true for 𝜾23 in HO.

Asymmetry in P𝝂𝝂 and P𝝂e channels

7

Normal Ordering (NO), 𝜾13 = 8.54° (NuFit3.2)

Octant Sensitivity: True NO, Ordering Marginalised

8

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) curves for comparison. https://arxiv.org/abs/1902.02963

Octant Sensitivity: True IO, Ordering marginalised

9

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. T2K (4+4) + NO𝝃A (3+3) curves for comparison. https://arxiv.org/abs/1902.02963

Octant Sensitivity (for range of 𝜾23 values):

10

A 3𝛕 sensitivity is obtained for 41.5° > 𝜾23 > 49° if NO is the true ordering (left). T2K (3 years neutrino mode) + NO𝝃A (3+3) lines for comparison. https://arxiv.org/abs/1302.1370

Summary:

1) Preliminary estimation of octant sensitivity projection with 3 years of ORCA115 has been presented. 2) Neutrino mass ordering is not a source of ambiguity in the octant determination at ORCA. 3) Study octant sensitivity in the presence of new physics will involve further degeneracies apart from the standard 8 fold ordering - octant - CP violating phase factor degeneracy.

11

12

THANKS