Degeneracy between θ23 octant and neutrino non-standard interactions at DUNE

Abstract

We expound in detail the degeneracy between the octant of θ 23 and flavor-changing neutral-current non-standard interactions (NSI's) in neutrino propagation, considering the Deep Underground Neutrino Experiment (DUNE) as a case study. In the presence of such NSI parameters involving the e − µ (ε eµ ) and e − τ (ε eτ ) flavors, the ν µ → ν e andν µ →ν e appearance probabilities in long-baseline experiments acquire an additional interference term, which depends on one new dynamical CP-phase φ eµ/eτ . This term sums up with the well-known interference term related to the standard CP-phase δ creating a source of confusion in the determination of the octant of θ 23 . We show that for values of the NSI coupling (taken one at-a-time) as small as f ew % (relative to the Fermi coupling constant G F ), and for unfavorable combinations of the two CP-phases δ and φ eµ/eτ , the discovery potential of the octant of θ 23 gets completely lost.

Non-unitarity, sterile neutrinos, and non-standard neutrino interactions

“…From ref. [75] this degeneracy was expected for the phase of φ τ e = arg(α τ e ) ∼ π since δ CP = −π/2 and strong correlations between these two parameters are required in order to reproduce this degeneracy. Note that this degeneracy is partially lifted in the ND undeveloped scenario (right panels).…”

“…These are shown in figure 2, and have been noticed in the context of NSI 5 in refs. [72][73][74][75] (for other works on degeneracies among standard and non-standard parameters in DUNE see e.g., refs. [76][77][78][79]).…”

Can nonstandard interactions jeopardize the hierarchy sensitivity of DUNE?

“…Among these, non-standard interactions have received a lot of attention lately specially * Email Address: deepthi@prl.res.in † Email Address: sruba@prl.res.in ‡ Email Address: newton@prl.res.in with the emergence of proposed next generation experiments like DUNE,T2HK, T2HKK etc. [4][5][6][7][8][9][10][11][12][13][14].…”

Fully constrained Majorana neutrino mass matrices using $$\varvec{\varSigma (72\times 3)}$$ Σ ( 72 × 3 )

“…The NuFIT data as well as other global fits [52,53] are showing a preference for nonmaximal atmospheric mixing. As a result there has been a lot of interest in the problem of octant degeneracy of θ 23 [54][55][56][57][58][59][60][61]. …”