arXiv subjects

Bikash Thapa

Publications and source records attributed to Bikash Thapa.

7 recordsLinked to original sources

arXiv2024

Resonant leptogenesis in minimal inverse seesaw ISS(2,2) model

We investigate the parameter space of the minimal inverse seesaw ISS(2,2) model for successful leptogenesis. The framework of ISS(2, 2) is realized by augmenting the Standard Model with two right-handed and two Standard Model singlet neutrinos. The decay of the heavy sterile states which is essentially an admixture of the right-handed and SM singlet neutrino states produces the baryon asymmetry of the universe. In this predictive model of leptogenesis, we study resonant leptogenesis where the mass splitting between the heavy sterile states is naturally achieved. We review the possibility of generating the observed baryon asymmetry of the universe via leptogenesis where the CP violation comes solely from the low-energy CP phases. In addition, we study the effect of texture zero in the Dirac mass matrix on the parameter space of the model for successful resonant leptogenesis.

hep-ph↗

arXiv2024

Neutrino Mixing and Resonant Leptogenesis in Inverse Seesaw and Δ(54) Flavor Symmetry

The current work involves augmenting the $Δ(54)$ discrete flavor model by incorporating two Standard Model Higgs particles into the Inverse Seesaw mechanism. We introduced Weyl fermions and Vector like fermions, which are gauge singlets in the Standard Model and produces Majorana mass terms in our lagrangian. The resulting mass matrix deviates from the tribimaximal neutrino mixing pattern producing a non-zero reactor angle ($θ_{13}$) . We have determined the effective Majorana neutrino mass, which is the parameter of relevance in neutrinoless double beta decay investigations, using the model's limited six-dimensional parameter space. We additionally investigate the possibility of baryogenesis in the proposed framework via resonant leptogenesis. We have the non-zero value for resonantly enhanced CP asymmetry originating from the decay of right-handed neutrinos at the TeV scale, accounting for flavor effects. The evolution of lepton asymmetry is systematically analyzed by numerically solving a set of Boltzmann equations, leading to the determination of the baryon asymmetry with a magnitude of $ \lvert η_B \rvert \approx 6 \times 10^{-10}$. This outcome is achieved by selecting specific values for the right-handed neutrino mass $M_1 = 10$ TeV and mass splitting, $d \approx 10^{-8}$.

hep-ph↗

arXiv2023

Neutrino Mass Model in the Context of $\boldsymbol{Δ(54) \otimes Z_2\otimes Z_3 \otimes Z_4}$ Flavor Symmetries with Inverse Seesaw Mechanism

Our analysis involves enhancing the $Δ(54)$ flavor symmetry model with Inverse Seesaw mechanism along with two SM Higgs through the incorporation of distinct flavons. Additionally, we introduce supplementary $Z_2\otimes Z_3 \otimes Z_4$ symmetries to eliminate any undesirable components within our investigation. The exact tri-bimaximal neutrino mixing pattern undergoes a deviation as a result of the incorporation of extra flavons, leading to the emergence of a non-zero reactor angle $θ_{13}$ that aligns with the latest experimental findings. It was found that for our model the atmospheric oscillation parameter occupies the lower octant for normal hierarchy case. We also examine the parameter space of the model for normal hierarchy to explore the Dirac CP ($δ_{CP}$), Jarlskog invariant parameter ($J$) and the Neutrinoless double-beta decay parameter ($m_{ββ}$) and found it in agreement with the neutrino latest data. Hence our model may be testable in the future neutrino experiments.

hep-ph↗

arXiv2023

A minimal inverse seesaw model with $S_4$ flavour symmetry

We construct an $S_4$ flavour symmetric minimal inverse seesaw model where the standard model is extended by adding two right-handed and two standard model gauge singlets neutrinos to explain the origin of tiny neutrino masses. The resulting model describes the lepton mass spectra and flavour mixing quite well for the case of the normal hierarchy of neutrino masses. The prediction of the model on the Dirac CP-violating phase is centered around $370.087^\circ$. Furthermore, using the allowed region for the model parameters, we have calculated the value of the effective Majorana neutrino mass, $\lvert\langle m_{ee}\rangle\rvert$, which characterizes neutrinoless double beta decay.

hep-ph↗

arXiv2023

Non-zero $θ_{13}$, CP-violation and Neutrinoless Double Beta Decay for Neutrino Mixing in the $A_4\times Z_2\times Z_3$ Flavor Symmetry Model

We study the modification of the Altarelli-Feruglio $A_4$ flavor symmetry model by adding three singlet flavons $ξ'$, $ξ''$ and $ρ$ and the model is augmented with extra $Z_2\times Z_2^ \prime$ symmetry to prevent the unwanted terms in our study. The addition of these three flavons lead to two higher order corrections in the form of two perturbation parameters $ε$ and $ε^\prime$. These corrections yield the deviation from exact tri-bimaximal (TBM) neutrino mixing pattern by producing a non-zero $θ_{13}$ and other neutrino oscillation parameters which are consistent with the latest experimental data. In both the corrections, the neutrino masses are generated via Weinberg operator. The analysis of the perturbation parameters $ε$ and $ε^\prime$, shows that normal hierarchy (NH) and inverted hierarchy (IH) for $ε$ does not change much. However, as the values of $ε^\prime$ increases, $θ_{23}$ occupies the lower octant for NH case. We further investigate the neutrinoless double beta decay parmeter $m_{ββ}$ using the parameter space of the model for both normal and inverted hierarchies of neutrino masses.

hep-ph↗

arXiv2022

Connecting low-energy CP violation, resonant leptogenesis and neutrinoless double beta decay in a radiative seesaw model

We present a study of resonant leptogenesis in a radiative seesaw model. We consider the case where two quasi-degenerate right-handed neutrinos realize resonant leptogenesis, and the CP violation necessary to achieve leptogenesis occurs through the CP phases present in the neutrino mixing matrix. A numerical analysis is performed by taking the best-fit values from the current global data for three neutrino mixing angles and two mass-squared differences. We have shown how the predicted value of baryon asymmetry depends on the Dirac and Majorana CP phases. With the particular choice for the mass parameters, this model prefers a normal hierarchy of neutrino masses based on the value of baryon asymmetry predicted. Using the constrained CP phases, we evaluate the effective neutrino mass, which is relevant to the neutrinoless double beta decay.

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arXiv2021

Resonant leptogenesis and TM$_1$ mixing in minimal Type-I seesaw model with S$_4$ symmetry

We present an S$_4$ flavour symmetric model within a minimal seesaw framework resulting in mass matrices that leads to TM$_1$ mixing. Minimal seesaw is realized by adding two right-handed neutrinos to the Standard Model. The model predicts Normal Hierarchy (NH) for neutrino masses. Using the constrained six-dimensional parameter space, we have evaluated the effective Majorana neutrino mass, which is the parameter of interest in neutrinoless double beta decay experiments. The possibility of explaining baryogenesis via resonant leptogenesis is also examined within the model. A non-zero, resonantly enhanced CP asymmetry generated from the decay of right-handed neutrinos at the TeV scale is studied, considering flavour effects. The evolution of lepton asymmetry is discussed by solving the set of Boltzmann equations numerically and obtain the value of baryon asymmetry to be $\lvert η_B \rvert = 6.3 \times 10^{-10}$.

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