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 1 14 Jan. 2020 | N. R. Khan Chowdhury | ORCA Phone Call |

Octant degeneracy The ambiguity in the determination of 𝜾 23 can be from two sources, 1) Inherent octant degeneracy: Oscillation and survival probabilities are function of sin 2 2 𝜾 23 . 2) Degeneracy of the octant with other oscillation parameters: oscillation and survival probabilities are function of sin 2 𝜾 23 or cos 2 𝜾 23 . Probabilities become identical for value of 𝜾 23 in opposite octant for different value of 𝜾 13 and 𝜺 CP . 2

Octant ambiguity ensued in P 𝝂 e and P ee The relevant probabilities in the OMSD approximation with matter effects reads m reaches value of 1 irrespective of the value of 𝜾 13 in vacuum and the During matter resonance, sin2 𝜾 13 product is no longer invariant for opposite octants for different values of 𝜾 13 . The electron survival probability is independent of 𝜾 23 and does not contribute to octant sensitivity. 3

P 𝝂 e in light of non-zero 𝜾 13 For 𝜾 23 in lower octant (solid line), higher values of 𝜾 13 (~8.9°) can give a higher octant sensitivity since the solid line is more separated from the wrong 𝜾 23 band (dashed lines) of variation of the probability over the whole range of test 𝜾 13 . The reverse is true for 𝜾 23 in HO. 4

Octant ambiguity ensued in P 𝝂𝝂 Leading terms (octant degenerate) sub-leading term lifting the degeneracy The strong octant sensitive behaviour of sin 4 𝜾 23 sin 2 2 𝜾 13 m near resonance can override the degeneracy since 𝜾 13 in matter gets amplified to maximal values. 5

P 𝝂𝝂 in light of non-zero 𝜾 13 The effect of 𝜾 13 on the separation between opposite bands is less, since the dominated by intrinsic octant degeneracy. Yet, for 𝜾 23 in lower octant (solid line), lower values of 𝜾 13 (~8.1°) can give a higher octant sensitivity since the solid line is more separated from the wrong 𝜾 23 band (dashed lines). The reverse is true for 𝜾 23 in HO. 6

Asymmetry in P 𝝂𝝂 and P 𝝂 e channel Normal Ordering, 𝜾 13 = 8.54° (NuFit3.2) 7

Octant Sensitivity: True NO T2K (4+4) + NO 𝝃 A (3+3) 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 𝛙 2 is lower for true HO in general. 𝛙 2 = (N LO(HO) - N HO(LO) ) 2 / N HO(LO) for true HO (LO). Although the numerator remains the same, the denominator is larger for true HO resulting in lower sensitivity. 8

Octant Sensitivity: True IO 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. 9

Octant Sensitivity: T2K (3 years neutrino mode) + NO 𝝃 A (3+3). 10

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. 11

THANKS 12