arXiv subjects

Vivek Kumar Nautiyal

Publications and source records attributed to Vivek Kumar Nautiyal.

7 recordsLinked to original sources

arXiv2026

Anomalous Matter Potentials in Earth's Inner Core: A Phenomenological Probe of Dark Matter and Light Sterile Neutrinos

Standard treatments of Earth matter effects in neutrino oscillation experiments assume that the coherent forward scattering potential experienced by propagating neutrinos is sourced entirely by the Standard Model electron density predicted by the Preliminary Reference Earth Model (PREM). We examine how an anomalous matter potential localized in Earth's inner core, motivated by gravitationally captured dark matter or resonant mixing of active neutrinos with a light (eV-scale or lighter) sterile state, would distort the vu survival and vutove appearance probabilities relative to the Standard Model PREM expectation. Using a full three-flavor matrix-exponentiation propagation code with a four-shell PREM density profile, we parametrize the new-physics contribution as a fractional enhancement ecore of the electron-sector potential confined to the inner core (r<1221 km) and compute oscillation probabilities for near-vertically upgoing atmospheric neutrinos (L=8000to12742km). Trajectories that do not cross the inner core (L<=12500km) are essentially insensitive to ecore, reproducing the Standard Model expectation to better than 0.1%. In contrast, near-antipodal trajectories crossing the inner core (L>=12505km, corresponding to nadir angles within roughly half a degree of the vertical) show significant effects. The muon-neutrino survival probability is displaced by tens of percent for ecore=0.05to0.15 and by more than 100% at particular energies for the νμ to νe appearance channel, with a pronounced neutrinoantineutrino asymmetry that mimics, but is physically distinct from, intrinsic CP violation. These results indicate that percent-level new-physics potentials confined to the inner core are within the discovery reach of high-statistics atmospheric neutrino telescopes such as IceCube Upgrade, KM3NeT/ORCA, and next-generation megaton-scale detectors.

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arXiv2026

Matter-Induced CPT Violation and Earth-Density Stratification Effects in Long-Baseline Neutrino Oscillation Experiments

We present a unified analysis of two matter-potential systematics in long-baseline (LBL) neutrino oscillation experiments. Matter-induced extrinsic CPT violation produces a non-zero asymmetry $A_{μe}^{CPT} = (P_{μe} - P_{\barμ\bar{e}})/(P_{μe} + P_{\barμ\bar{e}})$, computed here with exact three-flavour matrix-exponentiation propagators for T2K, NO$ν$A, DUNE, and Hyper-Kamiokande; values range from 0.022 to 0.180 at the respective peak energies and differ by up to 9\% between normal and inverted mass orderings. The three-dimensional surface $A_{μe}^{CPT}(E, δ_{CP})$ at the DUNE baseline reveals an entanglement between extrinsic CPT violation and intrinsic CP violation in the high-$L/E$ regime that requires joint statistical treatment. Concurrently, replacing the Preliminary Reference Earth Model (PREM) with a constant path-averaged density introduces a $δ_{CP}$-reconstruction bias below $0.3^{\circ}$ for $L \leq 5000$ km but growing to $17.8^{\circ}$ at $L = 7000$ km and $172.2^{\circ}$ at $L = 12000$ km. Since both effects share the same matter-potential Hamiltonian they must be modelled jointly; a Poisson log-likelihood $χ^2$ statistic with nuisance-parameter pull terms is used to quantify the bias.

hep-ph↗

arXiv2026

Matter Profile Mismodeling as the Origin of the CP CPT Degeneracy in Long-Baseline Neutrino Oscillation

We demonstrate that approximating the Earth's density profile with a single path averaged value instead of the spatially resolved Preliminary Reference Earth Model PREM generates a joint parameter degeneracy in the $(δ_{\text{CP}}, Δ_{\text{CPT}}, θ_{\text{CPT}})$ space. At long baselines ($L \geq 5000\text{ km}$), this geometric artifact becomes entirely indistinguishable from genuine Beyond the Standard Model (BSM) physics. While previous studies established individual channel biases separately, this work provides the first analytic proof that these biases form an extended two dimensional valley within the full three-parameter space. Furthermore, we rigorously demonstrate that multi channel combinations alone are insufficient to resolve this degeneracy. A Poisson loglikelihood chi square analysis confirms that DUNE like exposures utilizing a constant density approximation would erroneously report this artifact as a $\pm3σ$ BSM discovery. Specifically, at $L = 7000\text{ km}$, the constant-density assumption shifts the recovered $δ_{\text{CP}}$ by $17.8^\circ$ and fabricates a spurious CPT violation at $Δ_{\text{CPT}} = 4.1 \times 10^{-4}\text{ eV}^2$. Consequently, full spatially resolved PREM propagation is established as a strict mathematical requirement rather than an optional refinement for the correct physical interpretation of data from next-generation long baseline experiments, including DUNE, HyperKamiokande, and P2O.

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arXiv2021

Matter Effects on Mass Square Difference for Four Flavor Neutrino Oscillation

We consider the matter effects on four flavor neutrino oscillation scheme (3+1). In presence of sterile neutrino, the simplest four flavor neutrino mixing there are six mixing angles and three Dirac CP phases. In this paper, we discuss about the sensitivity of mass square difference effects Delta21, Delta31, and Delta41 in the matter. We find that in presence of sterile neutrino for four flavor mixing framework, only solar mass square difference Delta21 and atmospheric neutrino mass square difference Delta31 change for different values of Dirac phases and energy. There is no change of sterile neutrino mass square differences. In this letter, we study the matter effects on neutrino mass square differences Delta21, Delta31, and Delta41 and calculate the percentage change with respect to the mass square difference in the matter by varying energy for four flavor framework.

hep-ph↗

arXiv2021

Analytical Approach of Matter Effect on (3+1) Neutrino Oscillation

Abstract We study the analytic expression for four flavor neutrino oscillation in the presence of matter. We calculate the time evolution operator on flavor and mass basis. We find the matter dependent mass square difference and neutrino transition probabilities for (3+1) four flavor neutrino oscillation.

hep-ph↗

arXiv2021

Neutrino Mass Eigenvalues for Different Scheme within Four Flavor Neutrino framework

In this paper, we discuss neutrino mass eigenvalues for four flavor neutrino mixing. An extra mass states, in four flavor mixing and possible various combination of CP violating Majorana phases effects the neutrino mass eigenvalues. We have considered the effective Majorana mass m_{e}, related for \,\left(ββ\right)_{0ν\,} decay. In calculation, we consider two different neutrino mass orders, normal and inverted. We find the limits for neutrino mass eigenvalue m_{i} in the different neutrino mass spectrum and the sum of all four neutrino masses is \text{Σ}\text{\ensuremath{\equiv}}m_{1}+m_{2}+m_{3}+m_{4}>1.3\,eV\, which is relevant for cosmological observations and explain the different neutrino oscillations data.

hep-ph↗

arXiv2021

Large Changes of Atmospheric Mixing Angle $θ_{23}$ with Four Flavor Mixing from Planck Scale Effects

We consider the effects of Planck scale on four flavour neutrino mixings. The gravational interaction at $M_{x}=M_{\rm planck}$, we find that for degenerate neurino mass order, the Planck scale effects changes the mixing angle $θ'_{23}$, $θ'_{12}$ values and $θ'_{13}$, $θ'_{14}$, $θ'_{34}$, $θ'_{24}$ are unchanged above the GUT scale. In this paper, we study neutrino mixing in four flavor above the GUT scale.

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