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 singlet 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°. Furthermore, using the allowed region for the model parameters, we have calculated the value of the effective Majorana neutrino mass, |〈m  ee 〉|, which characterizes neutrinoless double beta decay.

India

Bikash Thapa

Sunita Barman

Sompriti Bora

N. Francis

A minimal inverse seesaw model with S4 flavour symmetry

Our analysis involves enhancing the <math><mi>Δ</mi><mo>(</mo><mn>54</mn><mo>)</mo></math> flavor symmetry model with Inverse Seesaw mechanism along with two SM Higgs through the incorporation of distinct flavons. Additionally, we introduce supplementary <math><msub><mrow><mi>Z</mi></mrow><mrow><mn>2</mn></mrow></msub><mo>⊗</mo><msub><mrow><mi>Z</mi></mrow><mrow><mn>3</mn></mrow></msub><mo>⊗</mo><msub><mrow><mi>Z</mi></mrow><mrow><mn>4</mn></mrow></msub></math> 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 <math><msub><mrow><mi>θ</mi></mrow><mrow><mn>13</mn></mrow></msub></math> 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 (<math><msub><mrow><mi>δ</mi></mrow><mrow><mi>C</mi><mi>P</mi></mrow></msub></math>), Jarlskog invariant parameter (J) and the Neutrinoless double-beta decay parameter (<math><msub><mrow><mi>m</mi></mrow><mrow><mi>β</mi><mi>β</mi></mrow></msub></math>) and found it in agreement with the neutrino latest data. Hence our model may be testable in the future neutrino experiments.

Hrishi Bora

Ng. K. Francis

Animesh Barman

Neutrino mass model in the context of Δ(54)⊗ ⊗ ⊗ flavor symmetries with Inverse Seesaw mechanism

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.

Ng.K. Francis

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

We present an S $$_4$$  <math> <msub> <mrow></mrow> <mn>4</mn> </msub> </math>   flavour symmetric model within a minimal seesaw framework resulting in mass matrices that leads to TM $$_1$$  <math> <msub> <mrow></mrow> <mn>1</mn> </msub> </math>   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 of the model, 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  $$|\eta _B| = 6.3 \times 10^{-10}$$  <math> <mrow> <mrow> <mo>|</mo> </mrow> <msub> <mi>η</mi> <mi>B</mi> </msub> <mrow> <mo>|</mo> <mo>=</mo> <mn>6.3</mn> <mo>×</mo> </mrow> <msup> <mn>10</mn> <mrow> <mo>-</mo> <mn>10</mn> </mrow> </msup> </mrow> </math>   with the choice of right-handed neutrino mass,  $$M_1 = 10$$  <math> <mrow> <msub> <mi>M</mi> <mn>1</mn> </msub> <mo>=</mo> <mn>10</mn> </mrow> </math>   TeV and mass splitting,  $$d \simeq 10^{-8}$$  <math> <mrow> <mi>d</mi> <mo>≃</mo> <msup> <mn>10</mn> <mrow> <mo>-</mo> <mn>8</mn> </mrow> </msup> </mrow> </math>  .

Ng. Francis

Resonant leptogenesis and TM $$_1$$  <math> <msub> <mrow></mrow> <mn>1</mn> </msub> </math>   mixing in minimal type-I seesaw model with S $$_4$$  <math> <msub> <mrow></mrow> <mn>4</mn> </msub> </math>   symmetry