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A bstract The anomalies in the measurements of observables involving b → sμμ decays, namely R K , R K * , P 5 ′ , and B s ϕ , may be addressed by adding lepton-universality-violating new physics contributions to the effective operators O 9 , O 10 , O 9 ′ , O 10 ′ . We analyze all the scenarios where the new physics contributes to a pair of these operators at a time. We perform a global fit to all relevant data in the b → s sector to estimate the corresponding new Wilson coefficients, O 9 N P , O 10 N P , O 9 ′ , O 10 ′ . In the light of the new data on R K , and R K * , presented in Moriond 2019, we find that the scenarios with new physics contributions to the O 9 N P O 9 ′ or O 9 N P O 10 ′ pair remain the most favored ones. On the other hand, though the competing scenario O 9 N P O 10 N P remains attractive, its advantage above the SM reduces significantly due to the tension that emerges between the R K and R K * measurements with the new data. The movement of the R K measurement towards unity would also result in the re-emergence of the one-parameter scenario C 9 NP  = −  C 9 ′ .

A bstract Neutrinos can acquire “refractive masses” as a consequence of their interactions with ultralight dark matter (DM). We explore a model with two additional sterile neutrinos and an ultralight scalar field which acts as DM and interacts with all five neutrinos. We show that the effective 5 × 5 Hamiltonian for neutrino propagation can be diagonalized by a unitary matrix ℙ parametrized by 6 mixing angles and 1 complex phase. When active-sterile mixing angles are small, we identify a parametrization for ℙ that reduces neutrino propagation inside the Sun to a two-flavor problem for a uniform DM background. In the presence of a DM halo inside the Sun, however, the propagation shows additional features in the region of halo dominance. We derive approximate analytic expressions for the electron neutrino survival probability in the presence of the DM halo. We show that this probability has a strong dependence on the neutrino production region even for a fixed energy, and numerically calculate the effects of averaging over these production regions. Comparisons with the re-interpreted solar data, in the light of possible active-sterile neutrino conversions, would allow putting bounds on the halo parameters. Finally, we examine the possibility of reviving the dark-LMA solution in this context, where the survival probability spectrum can have attractive features aligned with the measurements at Super-Kamiokande.

A bstract We propose a new approach to explore the neutral-current non-standard neutrino interactions (NSI) in atmospheric neutrino experiments using oscillation dips and valleys in reconstructed muon observables, at a detector like ICAL that can identify the muon charge. We focus on the flavor-changing NSI parameter ε μτ , which has the maximum impact on the muon survival probability in these experiments. We show that non-zero ε μτ shifts the oscillation dip locations in L / E distributions of the up/down event ratios of reconstructed μ − and μ + in opposite directions. We introduce a new variable ∆ d representing the difference of dip locations in μ − and μ + , which is sensitive to the magnitude as well as the sign of ε μτ , and is independent of the value of Δ m 32 2 . We further note that the oscillation valley in the ( E , cos θ ) plane of the reconstructed muon observables bends in the presence of NSI, its curvature having opposite signs for μ − and μ + . We demonstrate the identification of NSI with this curvature, which is feasible for detectors like ICAL having excellent muon energy and direction resolutions. We illustrate how the measurement of contrast in the curvatures of valleys in μ − and μ + can be used to estimate ε μτ . Using these proposed oscillation dip and valley measurements, the achievable precision on |ε μτ | at 90% C.L. is about 2% with 500 kt·yr exposure. The effects of statistical fluctuations, systematic errors, and uncertainties in oscillation parameters have been incorporated using multiple sets of simulated data. Our method would provide a direct and robust measurement of ε μτ in the multi-GeV energy range.

Atmospheric neutrino experiments can show the “oscillation dip” feature in data, due to their sensitivity over a large L/E range. In experiments that can distinguish between neutrinos and antineutrinos, like INO, oscillation dips can be observed in both these channels separately. We present the dip-identification algorithm employing a data-driven approach – one that uses the asymmetry in the upward-going and downward-going events, binned in the reconstructed L/E of muons – to demonstrate the dip, which would confirm the oscillation hypothesis. We further propose, for the first time, the identification of an “oscillation valley” in the reconstructed (Eμ,cosθμ) plane, feasible for detectors like ICAL having excellent muon energy and direction resolutions. We illustrate how this two-dimensional valley would offer a clear visual representation and test of the L/E dependence, the alignment of the valley quantifying the atmospheric mass-squared difference. Owing to the charge identification capability of the ICAL detector at INO, we always present our results using μ- and μ+ events separately. Taking into account the statistical fluctuations and systematic errors, and varying oscillation parameters over their currently allowed ranges, we estimate the precision to which atmospheric neutrino oscillation parameters would be determined with the 10-year simulated data at ICAL using our procedure.

A bstract Atmospheric neutrinos provide a unique avenue to explore the internal structure of Earth based on weak interactions, which is complementary to seismic studies and gravitational measurements. In this work, we demonstrate that the atmospheric neutrino oscillations in the presence of Earth matter can serve as an important tool to locate the core-mantle boundary (CMB). An atmospheric neutrino detector like the proposed 50 kt magnetized ICAL at INO can observe the core-passing neutrinos efficiently. These neutrinos would have experienced the MSW resonance and the parametric or neutrino oscillation length resonance. The net effect of these resonances on neutrino flavor conversions depends upon the location of CMB and the density jump at that radius. We quantify the capability of ICAL to measure the location of CMB in the context of multiple three-layered models of Earth. For the model where the density and the radius of core are kept flexible while the mass and radius of Earth as well as the densities of outer and inner mantle are fixed, ICAL can determine the location of CMB with a 1 σ precision of about 250 km with an exposure of 1000 kt yr. With the 81-layered PREM profile, this 1 σ precision would be about 350 km. The charge identification capability of ICAL plays an important role in achieving this precision.

A bstract Atmospheric neutrinos probe the interior of Earth using weak interactions, and provide information complementary to that of gravitational and seismic measurements. While passing through Earth, multi-GeV neutrinos encounter matter effects due to the coherent forward scattering with ambient electrons, which alter the neutrino oscillation probabilities. These matter effects depend upon the density distribution of electrons inside Earth, and hence, can be used to determine the internal structure of Earth. In this work, we employ a five-layered model of Earth where the layer densities and radii are modified, keeping the mass and moment of inertia of Earth unchanged and respecting the hydrostatic equilibrium condition. We use the proposed INO-ICAL detector as an example of an atmospheric neutrino experiment that can distinguish between neutrinos and antineutrinos efficiently in the multi-GeV energy range. Our analyses demonstrate that such an experiment can simultaneously constrain density jumps inside Earth and locate the core-mantle boundary. The charge identification (CID) capability of the ICAL detector would play a crucial role in obtaining these correlated constraints. An ICAL-like detector without CID capability would also be able to perform this task, albeit with a reduced sensitivity.

A bstract We analyze the class of models with an extra U(1) X gauge symmetry that can account for the b → sℓℓ anomalies by modifying the Wilson coefficients C 9 e and C 9 μ of the operators O 9 ℓ ≡ b ¯ γ μ P L s ℓ ¯ γ μ ℓ from their standard model values. At the same time, these models generate appropriate quark mixing, and give rise to neutrino mixing via the Type-I seesaw mechanism. Apart from the gauge boson Z′ , these frugal models only have three right-handed neutrinos for the seesaw mechanism, an additional SU(2) L scalar doublet for quark mixing, and a SM-singlet scalar that breaks the U(1) X symmetry. This set-up identifies a class of leptonic symmetries, and necessitates non-zero but equal charges for the first two quark generations. If the quark mixing beyond the standard model were CKM-like, all these symmetries would be ruled out by the latest flavor constraints on Wilson coefficients and collider constraints on Z′ parameters. However, we identify a single-parameter source of non-minimal flavor violation that allows a wider class of U(1) X symmetries to be compatible with all data. We show that the viable leptonic symmetries have to be of the form L e ± 3 L μ − L τ or L e − 3 L μ + L τ , and determine the ( M Z′ , g Z′ ) parameter space that may be probed by the high-luminosity data at the LHC.

A bstract We present compact analytic expressions for 3-flavor neutrino oscillation probabilities with invisible neutrino decay, where matter effects have been explicitly included. We take into account the possibility that the oscillation and decay components of the effective Hamiltonian do not commute. This is achieved by employing the techniques of inverse Baker-Campbell-Hausdorff (BCH) expansion and the Cayley-Hamilton theorem applied in the 3-flavor framework. If only the vacuum mass eigenstate ν 3 decays, we show that the treatment of neutrino propagation may be reduced to an effective 2-flavor analysis in the One Mass Scale Dominance (OMSD) approximation. The oscillation probabilities for P μμ , P ee , P eμ and P μe — relevant for reactor, long baseline and atmospheric neutrino experiments — are obtained as perturbative expansions for the case of only ν 3 decay, as well as for the more general scenario where all components of the decay matrix are non-zero. The analytic results thus obtained match the exact numerical results for constant density matter to a high precision and provide physical insights into possible effects of the decay of neutrinos as they propagate through Earth matter. We find that the effects of neutrino decay are most likely to be observable in P μμ . We also point out that at any long baseline, the oscillation dips in P μμ can show higher survival probabilities in the case with decay than without decay, and explain this feature using our analytic approximations.

A bstract We perform a detailed analysis for the prospects of detecting active-sterile oscillations involving a light sterile neutrino, over a large Δ m 41 2 range of 10 −5 eV 2 to 10 2 eV 2 , using 10 years of atmospheric neutrino data expected from the proposed 50 kt magnetized ICAL detector at the INO. This detector can observe the atmospheric ν μ and ν ¯ μ separately over a wide range of energies and baselines, making it sensitive to the magnitude and sign of Δ m 41 2 over a large range. If there is no light sterile neutrino, ICAL can place competitive upper limit on | U μ 4 | 2 ≲ 0 . 02 at 90% C.L. for Δ m 41 2 in the range (0 . 5−5)×10 −3 eV 2 . For the same |Δ m 41 2 | range, ICAL would be able to determine its sign, exploiting the Earth’s matter effect in μ − and μ + events separately if there is indeed a light sterile neutrino in Nature. This would help identify the neutrino mass ordering in the four-neutrino mixing scenario.

A bstract The India-based Neutrino Observatory (INO) will host a 50 kt magnetized iron calorimeter (ICAL@INO) for the study of atmospheric neutrinos. Using the detector resolutions and efficiencies obtained by the INO collaboration from a full-detector GEANT4-based simulation, we determine the reach of this experiment for the measurement of the atmospheric neutrino mixing parameters . We also explore the sensitivity of this experiment to the octant of θ 23 , and its deviation from maximal mixing.