arXiv subjects

Rukmani Mohanta

Publications and source records attributed to Rukmani Mohanta.

At least 37 records · Page 2Linked to original sources

arXiv2025

Directional Neutrino Bursts from Spinning and Moving Primordial Black Holes

We show that primordial black holes (PBHs) with significant spin and bulk motion produce sharply collimated neutrino bursts from Hawking evaporation, arising from the interplay of spin-induced angular anisotropy and relativistic Doppler boosting. This effect shifts the neutrino spectrum into the multi-GeV to hundreds of GeV range, where atmospheric backgrounds drop steeply, and enhances the flux by orders of magnitude within a narrow forward cone. We compute the full lab-frame neutrino distribution and derive updated constraints on PBH number density from non-observation of such bursts in IceCube and KM3NeT. Our results identify directional high-energy neutrino bursts as a distinctive, testable signature of spinning PBHs, providing a complementary probe of the PBH dark matter hypothesis and Hawking radiation.

astro-ph.CO↗

arXiv2025

Probing neutrino mass ordering with supernova neutrinos at NO$ν$A including the effect of sterile neutrinos

In this work, we explore the possibility of probing the mass ordering sensitivity as a function of supernova distance in the context of the ongoing neutrino experiment NO$ν$A. We provide a detailed study of the active-active and active-sterile mixing frameworks, illustrating how supernova neutrinos can be used to realize the existence of sterile neutrinos. Interestingly, we infer that observation of the NC channel alone can differentiate between the presence and absence of sterile neutrinos. Our results indicate that the primary channel of NO$ν$A can distinguish normal mass ordering from inverted mass ordering at $5 σ$ confidence level for a supernova explosion occurring at a distance of 5 kpc. Additionally, we examine the impact of systematic uncertainties on mass ordering sensitivity, showing that higher levels of systematics lead to a reduction in sensitivity. Similarly, the inclusion of energy smearing significantly diminishes ordering sensitivity.

hep-ph↗

arXiv2025

Study of large extra dimension and neutrino decay at P2SO experiment

In this study, we explore two intriguing new physics scenarios: the theory of Large Extra Dimensions (LED) and the theory of neutrino decay. We analyze the impact of LED on neutrino oscillations in the contexts of Protvino to Super-ORCA (P2SO), DUNE, and T2HK, with a particular emphasis on P2SO. In contrast, the effects of neutrino decay are examined exclusively in the context of P2SO. For the LED scenario, we find that combining data from P2SO, DUNE, and T2HK can yield tighter constraints than current bounds, but only if all oscillation parameters are measured with high precision. In the case of neutrino decay, P2SO can achieve slightly better bounds compared to ESSnuSB and MOMENT, although its bounds remain weaker than those provided by DUNE and T2HK. Regarding sensitivities to unresolved oscillation parameters, the existence of LED has a minimal impact on the determination of CP violation, mass ordering and octant. However, neutrino decay can significantly influence the sensitivities related to CP violation and octant in a non-trivial manner.

hep-ph↗

arXiv2025

Unraveling New Physics Effects in $b \rightarrow s \ell_1 \ell_2$ Transitions with a Model-Independent Perspective

Motivated by recent anomalies in observables associated with flavor-changing neutral current (FCNC) transitions, specifically $b \rightarrow s \ell^+ \ell^-$ processes, we present a comprehensive analysis of lepton flavor-violating (LFV) decay modes mediated by $b \rightarrow s \ell_1 \ell_2$ transitions with $\ell_1 \neq \ell_2$. While such LFV processes are forbidden within the Standard Model (SM), they naturally arise in several of its extensions, including models featuring additional vector-like fermions and extra $Z'$ bosons. Employing the most general effective Hamiltonian for $b \rightarrow s \ell_1 \ell_2$ transitions, we derive the angular distributions of the relevant decay modes. Adopting a model-independent framework, we systematically study the LFV decays $B \rightarrow K^* \ell_1 \ell_2$, $B_s \rightarrow ϕ\ell_1 \ell_2$, $B \rightarrow K_2^* \ell_1 \ell_2$, and $Λ_b \rightarrow Λ\ell_1 \ell_2$. Although LFV mesonic decays have been widely explored, the corresponding baryonic decays remain comparatively under-investigated. We provide bounds on branching ratio ($\mathcal{B}$), forward-backward asymmetry ($\mathcal{A}_{FB}$), and longitudinal lepton polarization fraction ($\mathcal{F}_L$). Furthermore, considering the projected sensitivities of the LHCb upgrade and Belle II experiments, we estimate upper limits for these observables, offering promising avenues for probing new physics in these LFV channels.

hep-ph↗

arXiv2025

Neutrino Theory in the Precision Era

This document summarises discussions on future directions in theoretical neutrino physics, which are the outcome of a neutrino theory workshop held at CERN in February 2025. The starting point is the realisation that neutrino physics offers unique opportunities to address some of the most fundamental questions in physics. This motivates a vigorous experimental programme which the theory community fully supports. \textbf{A strong effort in theoretical neutrino physics is paramount to optimally take advantage of upcoming neutrino experiments and to explore the synergies with other areas of particle, astroparticle, and nuclear physics, as well as cosmology.} Progress on the theory side has the potential to significantly boost the physics reach of experiments, as well as go well beyond their original scope. Strong collaboration between theory and experiment is essential in the precision era. To foster such collaboration, \textbf{we propose to establish a CERN Neutrino Physics Centre.} Taking inspiration from the highly successful LHC Physics Center at Fermilab, the CERN Neutrino Physics Centre would be the European hub of the neutrino community, covering experimental and theoretical activities.

hep-ph↗

arXiv2025

Exploring Physics beyond the Standard Model with Neutrinos

Neutrinos, being elusive subatomic particles having only weak interactions, provide an ideal platform to look for physics beyond the Standard Model. In the present era of neutrino physics, various experiments are focusing towards the precision measurements of the oscillation parameters. Hence, various new physics scenarios which can affect the neutrino oscillation probabilities in matter, be in need of careful investigation. There is a slight tension at the level of $2 σ$ between the recently reported results on the CP violating phase $δ_{CP}$ by NOvA and T2K experiments, which can be attributed to the role of non-standard interactions (NSIs) in the propagation of neutrinos through matter. Another interesting possibility is that though neutrinos are electrically neutral, they can possess electromagnetic properties such as electric and magnetic dipole moments in the presence of new physics, and the neutrino oscillation experiments can put limits on them. In this work, we will focus on these two aspects and show how they can be used to probe the nature of new physics from model-building perspectives.

hep-ph↗

arXiv2025

The effect of non-standard interactions and environmental decoherence at DUNE

The Deep Underground Neutrino Experiment (DUNE) is a proposed long-baseline neutrino oscillation experiment that will project an on-axis wide-band neutrino beam over a distance of 1300 km to determine the unknowns in the neutrino sector. Given the baseline of 1300 km and the intense beam facility, DUNE is a promising experiment to study the sub-leading effects such as environmental decoherence, matter induced non-standard interactions (NSIs), neutrino decay, etc. In this study, we investigate how NSI and environmental decoherence affect the neutrino oscillation probabilities simultaneously. Considering the modified probabilities we obtain the updated mass hierarchy (MH) and CP violation (CPV) sensitivities of DUNE. Furthermore, we demonstrate the sensitivity of DUNE to distinguish between the effects of NSI and environmental decoherence.

hep-ph↗

arXiv2025

Delving into new physics in semileptonic $b \to c τ\bar ν$ transitions

Recently, several indications of lepton non-universality observables have been perceived in semileptonic $B$ meson decay processes, both in the neutral-current ($b \to s ll $) and charged-current ($b \to c l \bar ν_l$) transitions. Influenced by these fascinating quotients, we examine the semileptonic decays involving the $b \to c l \bar ν_l$ quark level transitions. We execute it through a model independent analysis in order to probe the nature of new physics. Taking into consideration the most general effective Hamiltonian, we scrutinize $Λ_b \to Λ_c τ\bar ν_τ$, $ B_c^+ \to η_c τ^+ ν_τ$, and $ B \to D^{**} τ\bar ν_τ$ (where $D^{**} = \{D^*_0, D_1^*, D_1, D_2^*\}$ are the four lightest excited charm mesons) processes, in the presence of new physics. We perform a global fit to different sets of new coefficients, making use of the measurements on $R_{D}$, $R_{D^{*}}$, $R_{J/ψ}$, $P_τ^{D^*}$ and the upper limit on Br($B_c^+ \to τ^+ ν_τ$). We then inspect the effect of constrained new couplings on the branching ratios, forward-backward asymmetry parameters, lepton non-universality ratios (LNU), lepton and hadron polarization asymmetries of these decay modes.

hep-ph↗

arXiv2025

Effect of torsion in long-baseline neutrino oscillation experiments

In this work we investigate the effect of curved spacetime on neutrino oscillation. In a curved spacetime, the effect of curvature on fermionic fields is represented by spin connection. The spin connection consists of a non-universal ``contorsion" part which is expressed in terms of vector and axial current density of fermions. The contraction of contorsion part with the tetrad fields, which connects the internal flat space metric and the spacetime metric, is called torsion. In a scenario where neutrino travels through background of fermionic matter at ordinary densities in a curved spacetime, the Hamiltonian of neutrino oscillation gets modified by the torsional coupling constants $λ_{21}^{\prime}$ and $λ_{31}^{\prime}$. The aim of this work is to study the effect of $λ_{21}^{\prime}$ and $λ_{31}^{\prime}$ in DUNE and P2SO. In our study we, (i) discuss the effect of torsional coupling constants on the neutrino oscillation probabilities, (ii) estimate the capability of P2SO and DUNE to put bounds on these parameters and (iii) study how the physics sensitivities get modified in presence of torsion.

hep-ph↗

arXiv2024

Exploring neutrino masses, $(g-2)_{μ, e}$ in type I+II seesaw in ${L^{}_e-L^{}_α}$ gauge extended model

This paper aims to explore the implications of $U(1)_{L_e-L_α}$ gauge symmetries, where $α=τ, μ$, in the neutrino sector through the type-(I+II) seesaw mechanisms. To achieve such a hybrid framework, we include a scalar triplet and three right-handed neutrinos. The model can successfully account for the active neutrino masses, mixing angles, mass squared differences, and the CP-violating phase within the $3 σ$ bounds of NuFit v5.2 neutrino oscillation data. The presence of new gauge boson at the MeV scale provides an explanation for the muon and electron $(g-2)$ within the confines of their experimental limits. Furthermore, we scrutinize the proposed models in the context of upcoming long-baseline neutrino experiments such as DUNE, P2SO, T2HK, and T2HKK. The findings reveal that P2SO and T2HK have the ability to probe both the models in their $5 σ$ allowed oscillation parameter region, whereas DUNE and T2HKK can conclusively test only model with $U(1)_{L_e-L_μ}$- symmetry within their $5 σ$ parameter space if the true values of the oscillation parameters remain consistent with NuFit v5.2.

hep-ph↗

arXiv2024

Study of Long Range Force in P2SO and T2HKK

In this paper we have studied the sensitivity of the future long-baseline neutrino experiments P2SO and T2HKK to the long-range force (LRF). In the context of these two experiments, our aim is to study: (i) the capability to put bounds on the LRF parameters, (ii) effect of LRF in the measurement of standard oscillation parameters and (iii) capability to constrain the mass of the new gauge boson and the value of new coupling constant, that gives rise to LRF due to matter density in Sun. In our study, we find that among the different neutrino experiments, the best bound on the LRF parameters including mass of the new gauge boson and the value of new coupling constant will come from the P2SO experiment. Our study also shows that LRF has non-trivial effect on the determination of the standard neutrino oscillation parameters except the precision of $Δm^2_{31}$. For this parameter, the precision remains unaltered in the presence of LRF for both these experiments.

hep-ph↗

arXiv2024

Predictions from scoto-seesaw with $A_4$ modular symmetry

This paper's novelty lies in introducing a hybrid scoto-seesaw model rooted in $A_4$ discrete modular symmetry leading to several interesting phenomenological implications. The scoto-seesaw framework leads to generation of one mass square difference $( Δm^2_{\rm atm}$) using the type-I seesaw mechanism at the tree level. Additionally, the scotogenic contribution is vital in obtaining the other mass square difference ($Δm^2 _{\rm sol}$) at the loop level, thus providing a clear interpretation of the two different mass square differences. The non-trivial transformation of Yukawa couplings under the $A_4$ modular symmetry helps to explore neutrino phenomenology with a specific flavor structure of the mass matrix. In addition to predictions for neutrino mass ordering, mixing angles and CP phases, this setup leads to precise predictions for $\sum m_i$ as well as $|m_{ee}|$. In particular, the model predicts $\sum m_i \in (0.073,0.097)$ eV and $\left| m_{ee}\right| \in (3.15,6.66)\times 10^{-3} $ eV range; within reach of upcoming experiments. Furthermore, our model is also promising for addressing lepton flavor violations, i.e., $\ell_α\to \ell_βγ$, $\ell_α\to 3\ell_β$ and $μ- e $ conversion rates while staying within the realm of current experimental limits.

hep-ph↗

arXiv2024

Study of Scalar Non Standard Interaction at Protvino to Super-ORCA experiment

In this paper we have studied the phenomenon of non-standard interaction mediated by a scalar field (SNSI) in the context of P2SO experiment and compared its sensitivity with DUNE. In particular, we have studied the capability of these two experiments to put bounds on the diagonal SNSI parameters i.e., $η_{ee}$, $η_{μμ}$ and $η_{ττ}$ and studied the impact of these parameters on the determination of neutrino mass ordering, octant of $θ_{23}$ and CP violation (CPV). In our analysis we find that, the parameter $Δm^2_{31}$ has a non-trivial role if one wants estimate the bounds on $η_{μμ}$ and $η_{ττ}$ assuming SNSI does not exist in nature. Our results show that sensitivity of P2SO and DUNE to constraint $η_{μμ}$ and $η_{ττ}$ are similar whereas the sensitivity of DUNE is slightly better for $η_{ee}$. We find that the mass ordering and CPV sensitivities are mostly affected by $η_{ee}$ compared to $η_{μμ}$ and $η_{ττ}$ if one assumes SNSI exists in nature. On the other hand, octant sensitivity is mostly affected by $η_{μμ}$ and $η_{ττ}$. These sensitivities can be either higher or lower than the standard three flavour scenario depending on the relative sign of the SNSI parameters. Regarding the precision of atmospheric mixing parameters, we find that the precision of $θ_{23}$ deteriorates significantly in the presence of $η_{μμ}$ and $η_{ττ}$.

hep-ph↗

arXiv2024

Correlating neutrino magnetic moment and scalar triplet dark matter to enlighten XENONnT bounds in a Type-II model

We investigate neutrino magnetic moment, triplet scalar dark matter in a Type-II radiative seesaw scenario. With three vector-like fermion doublets and two scalar triplets, we provide a loop level setup for the electromagnetic vertex of neutrinos. All the scalar multiplet components constitute the total dark matter abundance of the Universe and also their scattering cross section with detector lie below the experimental upper limit. Using the consistent parameter space in dark matter domain, we obtain light neutrino mass in sub-eV scale and also magnetic moment in the desired range. We further derive the constraints on neutrino transition magnetic moments, consistent with XENONnT limit.

hep-ph↗

arXiv2023

When Energy Goes Missing: New Physics in $b\to sνν$ with Sterile Neutrinos

Belle II recently reported the first measurement of $B^+\to K^++\mathrm{inv}$, which is $2.8σ$ above the Standard Model prediction. We explore the available parameter space of new physics within Standard Model effective field theory extended by sterile neutrinos ($ν$SMEFT) and provide predictions for the other $B\to K^{(\star)}+\mathrm{inv}$ decay modes and invisible $B_s$ decays. We also briefly comment on charged current decays $B\to D^{(\star)}\ell\barν$ and possible ultraviolet completions of the relevant $ν$SMEFT operators.

hep-ph↗

arXiv2023

Neutrino magnetic moment and inert doublet dark matter in a Type-III radiative scenario

We narrate dark matter, neutrino magnetic moment and mass in a Type-III radiative scenario. The Standard Model is enriched with three vector-like fermion triplets and two inert doublets to provide a suitable platform for the above phenomenological aspects. The inert scalars contribute to total relic density of dark matter in the Universe. Neutrino aspects are realized at one-loop with magnetic moment obtained through charged scalars, while neutrino mass gets contribution from charged and neutral scalars. Taking inert scalars up to $2$ TeV and triplet fermion in few hundred TeV range, we obtain a common parameter space, compatible with experimental limits associated with both neutrino and dark matter sectors. Using a specific region for transition magnetic moment (${\cal O} (10^{-11}μ_B$)), we explain the excess recoil events, reported by the XENON1T collaboration. Finally, we demonstrate that the model is able to provide neutrino magnetic moments in a wide range from $10^{-12}μ_B$ to $10^{-10}μ_B$, meeting the bounds of various experiments such as Super-K, TEXONO, Borexino and XENONnT.

hep-ph↗

arXiv2023

Determination of neutrino mass ordering from Supernova neutrinos with T2HK and DUNE

In this paper, we study the possibility of determining the neutrino mass ordering from the future supernova neutrino events at the DUNE and T2HK detectors. We estimate the expected number of neutrino event rates from a future supernova explosion assuming Garching flux model corresponding to different processes that are responsible for detecting the supernova neutrinos at these detectors. We present our results in the form of $χ^2$, as a function of supernova distance. For a systematic uncertainty of 5\% in normalisation as well as energy calibration error, our results show that, the neutrino mass ordering can be determined at $5 ~σ$ C.L. if the supernova explosion occurs at a distance of 42.7 kpc for T2HK and at a distance of 15.2 kpc for DUNE. Our results also show that the sensitivity of DUNE and T2HK get affected by the systematic uncertainties for the smaller supernova distances. Further, we show that in both DUNE and T2HK, the sensitivity gets deteriorated to some extent due to presence of energy smearing of the neutrino events. This occurs because of the reconstruction of the neutrino energy from the energy-momentum measurement of the outgoing leptons at the detector.

hep-ph↗

arXiv2023

Exploring Models with Modular Symmetry in Neutrino Oscillation Experiments

Our study aims to investigate the viability of neutrino mass models that arise from discrete non-Abelian modular symmetry groups, i.e., $Γ_N$ with ($N=1,2,3,\dots$) in the future neutrino experiments T2HK, DUNE, and JUNO. Modular symmetry reduces the usage of flavon fields compared to the conventional discrete flavor symmetry models. Theories based on modular symmetries predict the values of leptonic mixing parameters, and therefore, these models can be tested in future neutrino experiments. In this study, we consider three models based on the $A_4$ modular symmetry, i.e., Model-A, B, and C such a way that they predict different values of the oscillation parameters but still allowed with respect to the current data. In the future, it is expected that T2HK, DUNE, and JUNO will measure the neutrino oscillation parameters very precisely, and therefore, some of these models can be excluded in the future by these experiments. We have estimated the prediction of these models numerically and then used them as input to scrutinize these models in the neutrino experiments. Assuming the future best-fit values of $θ_{23}$ and $δ_{\rm CP}$ remain the same as the current one, our results show that at $5 σ$ C.L, Model-A can be excluded by T2HK whereas Model-B can be excluded by both T2HK and DUNE. Model-C cannot be excluded by T2HK and DUNE at $5 σ$ C.L. Further; our results show that JUNO alone can exclude Model-B at an extremely high confidence level if the future best-fit of $θ_{12}$ remains at the current-one. We have also identified the region in the $θ_{23}$ - $δ_{\rm CP}$ parameter space, for which Model-A cannot be separated from Model-B in T2HK and DUNE.

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