Sabya Sachi Chatterjee

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 (NSIs) 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 ( e e μ ) and e − τ ( e e τ ) flavors, the ν μ → ν e and ν ¯ μ → ν ¯ e appearance probabilities in long-baseline experiments acquire an additional interference term, which depends on one new dynamical CP-phase ϕ e μ / e τ . 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 few % (relative to the Fermi coupling constant G F ), and for unfavorable combinations of the two CP-phases δ and ϕ e μ / e τ , the discovery potential of the octant of θ 23 gets completely lost.

Physics reach of DUNE with a light sterile neutrino

A bstractWe investigate the implications of one light eV scale sterile neutrino on the physics potential of the proposed long-baseline experiment DUNE. If the future short-baseline experiments confirm the existence of sterile neutrinos, then it can affect the mass hierarchy (MH) and CP-violation (CPV) searches at DUNE. The MH sensitivity still remains above 5σ if the three new mixing angles (θ14, θ24, θ34) are all close to θ13. In contrast, it can decrease to 4σ if the least constrained mixing angle θ34 is close to its upper limit ∼ 300. We also assess the sensitivity to the CPV induced both by the standard CP-phase δ13 ≡ δ, and the new CP-phases δ14 and δ34. In the 3+1 scheme, the discovery potential of CPV induced by δ13 gets deteriorated compared to the 3ν case. In particular, the maximal sensitivity (reached around δ13 ∼ ± 900) decreases from 5σ to 4σ if all the three new mixing angles are close to θ13. It can further diminish to almost 3σ if θ34 is large (∼ 300). The sensitivity to the CPV due to δ14 can reach 3σ for an appreciable fraction of its true values. Interestingly, θ34 and its associated phase δ34 can influence both the νe appearance and νμ disappearance channels via matter effects, which in DUNE are pronounced. Hence, DUNE can also probe CPV induced by δ34 provided θ34 is large. We also reconstruct the two phases δ13 and δ14. The typical 1σ uncertainty on δ13 (δ14) is ∼ 200 (300) if θ34 = 0. The reconstruction of δ14 (but not that of δ13) degrades if θ34 is large.

Octant of

Present global fits of world neutrino data hint towards nonmaximal θ_{23} with two nearly degenerate solutions, one in the lower octant (θ_{23}π/4). This octant ambiguity of θ_{23} is one of the fundamental issues in the neutrino sector, and its resolution is a crucial goal of next-generation long-baseline (LBL) experiments. In this Letter, we address, for the first time, the impact of a light eV-scale sterile neutrino towards such a measurement, taking the Deep Underground Neutrino Experiment as a case study. In the so-called 3+1 scheme involving three active and one sterile neutrinos, the ν_{μ}→ν_{e} transition probability probed in the LBL experiments acquires a new interference term via active-sterile oscillations. We find that this interference term can mimic a swap of the θ_{23} octant, even if one uses the information from both neutrino and antineutrino channels. As a consequence, the sensitivity to the octant of θ_{23} can be completely lost, and this may have serious implications for our understanding of neutrinos from both the experimental and theoretical perspectives.

\theta_{23}

A bstractWe study the impact of one light sterile neutrino on the prospective data expected to come from the two presently running long-baseline experiments T2K and NOvA when they will accumulate their full planned exposure. Introducing for the first time, the bi-probability representation in the 4-flavor framework, commonly used in the 3-flavor scenario, we present a detailed discussion of the behavior of the vμ → ve and v¯μ→v¯e

Discovery potential of T2K and NOvA in the presence of a light sterile neutrino

{\overline{v}}_{\mu}\to {\overline{v}}_e

Signatures of a light sterile neutrino in T2HK

transition probabilities in the 3+1 scheme. We also perform a detailed sensitivity study of these two experiments (both in the stand-alone and combined modes) to assess their discovery reach in the presence of a light sterile neutrino. For realistic benchmark values of the mass-mixing parameters (as inferred from the existing global short-baseline fits), we find that the performance of both these experiments in claiming the discovery of the CP-violation induced by the standard CP-phase δ

Exploring Flavor-Dependent Long-Range Forces in Long-Baseline Neutrino Oscillation Experiments

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