Abstract
The possibility of Lorentz Invariance Violation (LIV) may appear in unified theories, such as string theory, which allow the existence of a new space-time structure at the Planck scale (Mp ∼ 1019 GeV). This effect can be observed at low energies with a strength of ∼ 1/Mp using the perturbative approach. In the minimal Standard Model extension (SME) framework, the neutrino mass-induced flavor oscillation gets modified in the presence of LIV. The Iron Calorimeter (ICAL) detector at the proposed India-based Neutrino Observatory (INO) offers a unique window to probe these LIV parameters by observing atmospheric neutrinos and antineutrinos separately over a wide range of baselines in the multi-GeV energy range. In this paper, for the first time, we study in detail how the CPT-violating LIV parameters (aμτ, aeμ, aeτ) can alter muon survival probabilities and expected μ− and μ+ event rates at ICAL. Using 500 kt·yr exposure of ICAL, we place stringent bounds on these CPT-violating LIV parameters at 95% C.L., which are slightly better than the present Super-Kamiokande limits. We demonstrate the advantage of incorporating hadron energy information and charge identification capability at ICAL while constraining these LIV parameters. Further, the impact of the marginalization over the oscillation parameters and choice of true values of sin2θ23 on LIV constraints is described. We also study the impact of these LIV parameters on mass ordering determination and precision measurement of atmospheric oscillation parameters.
Highlights
Even an introduction of non-commutativity in space-time structure at local fields [12, 13] can give rise to a breaking of charge, parity, and time-reversal (CPT) symmetry, so-called CPT violation, which is a special case of Lorentz Invariance Violation (LIV) [14]
As we will demonstrate in the later part of the result section that Iron Calorimeter (ICAL) being an atmospheric neutrino experiment dominated by νμ → νμ survival channel places tightest constraint on aμτ among all the LIV parameters
We focus our attention on the isotropic CPT-violating LIV parameters aμτ, aeμ, and aeτ where we consider their real values only with both positive and negative signs
Summary
The study of atmospheric neutrinos provides an avenue to probe neutrino oscillations as an interferometer with a length scale of the diameter of Earth, which may get affected by the presence of LIV. For a large fraction of these baselines (5721 km to 12757 km), neutrinos pass through the inner mantle or even core, where the density changes significantly following the PREM [106] profile with a sharp jump in the density at the core-mantle boundary For these trajectories, the line-averaged constant Earth matter density approximation is no longer valid and a simple scaling between CPT-violating LIV and NC-NSI parameters does not work. Note that to study the impact of CPT-violating LIV parameters on the atmospheric neutrinos at INO-ICAL, we perform a full-fledged numerical simulation from scratch considering three-flavor neutrino oscillation probabilities in the presence of the PREM profile of Earth and obtain all the results that we show in the present paper. In this work, we use numerically calculated full three-flavor oscillation probabilities with LIV in the presence of Earth’s matter with the PREM profile [106]
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