Octant Degeneracy, Quadrant of leptonic CPV phase at Long Baseline Neutrino Experiments and Baryogenesis

In a recent work by us, we have studied, how CP violation discovery potential can be improved at long baseline neutrino experiments (LBNE/DUNE), by combining with its ND (near detector) and reactor experiments. In this work, we discuss how this study can be further analysed to resolve entanglement of the quadrant of leptonic CPV phase and Octant of atmospheric mixing angle $\theta_{23}$, at LBNEs. The study is done for both NH (Normal hierarchy) and IH (Inverted hierarchy), HO (Higher Octant) and LO (Lower Octant). We show how baryogenesis can enhance the effect of resolving this entanglement, and how possible values of the leptonic CP-violating phase $\delta_{CP}$ can be predicted in this context. With respect to the latest global fit data of neutrino mixing angles, we predict the values of $\delta_{CP}$ for different cases. In this context we present favoured values of $\delta_{CP}$ ($\delta_{CP}$ range at $\geq$ 2$\sigma$ ) constrained by the latest updated BAU range and also confront our predictions of $\delta_{CP}$ with an up-to-date global analysis of neutrino oscillation data. We find that some region of the favoured $\delta_{CP}$ parameter space lies within the best fit values around $\delta_{CP} \simeq 1.3\pi-1.4 \pi$. A detailed analytic and numerical study of baryogenesis through leptogenesis is performed in this framework in a model independent way.Comment: 14 pages, 5 figures, 2 Tables, New Analysi

Charged Lepton Flavor Violation μ→eγ\mu\rightarrow e\gamma in μ−τ\mu-\tau Symmetric SUSY SO(10) mSUGRA, NUHM, NUGM, and NUSM theories and LHC

Charged Lepton Flavor Violation (cLFV) processes like $\mu \rightarrow e \gamma$ are rare decay processes, that are another signature of physics beyond Standard Model (BSM). These processes have been studied in various models, that could explain neutrino oscillations and mixings. In this work, we present bounds on cLFV decay $\mu \rightarrow e \gamma$ in a $\mu$-$\tau$ symmetric SUSY SO(10) theory, using type I seesaw mechanism. The updated constraints on BR($\mu \rightarrow e \gamma$) from MEG experiment, recently measured value of Higgs mass at LHC and value of $\theta_{13}$ from reactor data have been used. We present our results in mSUGRA, NUHM, NUGM and NUSM models, and sensitivity to test these theories at next run of LHC is also discussed.Comment: 22 pages, 6 figures, 6 Table

A new viable mass region of Dark matter and Dirac neutrino mass generation in a scotogenic extension of SM

We propose a scotogenic extension of the Standard Model which can provide a scalar Dark Matter candidate in the new, theoretically previously unaddressed, intermediate region ($200\leq M_{DM}\leq 550$ GeV) and also generate light Dirac neutrino masses. In this framework, the standard model is extended by three gauge singlet fermions, two singlet scalar fields, and one additional scalar doublet, all of which are odd under $Z_{2} \times Z_{4}$ discrete symmetry. These additional symmetries prevent the singlet fermions from obtaining Majorana mass terms along with providing the stability to the dark matter candidate. It is known that in the case of the scalar singlet DM model, the only region which is not yet excluded is a narrow region close to the Higgs resonance $m_{S} \simeq\frac{m_{h}}{2}$ - others ruled out from different experimental and theoretical bounds. In the case of the Inert doublet model, the mass region ($\sim 60$-$80$ GeV) and the high mass region (heavier than $550$ GeV) are allowed. This motivates us to explore a parameter range in the intermediate-mass region $M_{W}\leq M_{DM}\leq 550$ GeV, which we do in a scotogenic extension of SM with a scalar doublet and scalar singlets. The dark matter in our model is a mixture of singlet and doublet scalars. We constrain the allowed parameter space of the model using Planck bound on present dark matter relic abundance, neutrino mass, and the latest bound on spin-independent DM-nucleon scattering cross-section from XENON1T experiment. Our model may provide a viable DM candidate in the new, previously unexplored mass range ($200\leq M_{DM}\leq 550$ GeV), if this new window for the DM candidate mass is detected in future experiments, along with explanation of Dirac mass of neutrinos, since so far there is no strong evidence in support of Majorana nature of neutrino mass.Comment: 16 pages, 7 figures, 1 tabl

Exploring the feasibility of the cLFV decay μ→e+γ \mu \rightarrow e + \gamma in inverse and linear seesaw mechanisms with A4A_4 flavour symmetry

Flavour symmetries are required to explain the observed flavour structure of fundamental particles. In this work, we investigate the rare charged lepton flavour violating (cLFV) decay process ($\mu \rightarrow e\gamma$) in two of the low scale ($\sim$TeV) seesaw models: (i) the Inverse seesaw (ISS) and (ii) Linear seesaw (LSS) models within the framework of $A_{4}$ flavour symmetry. Apart from the $A_{4}$ flavour symmetry, some other symmetries like $U(1)_{X}$, $Z_4$ and $Z_5$ are included to construct the Lagrangian. We use results from our previous work where we computed unknown neutrino oscillation parameters within $3 \sigma$ limits of their global best fit values, and apply those results to compute the branching ratio (BR) of the muon decay for both the seesaw models. Next we compare our results with the current experimental bounds and sensitivity limits of BR($\mu \rightarrow e\gamma$) as projected by various experiments, and present a comparative analysis that which of the two models is more likely to be tested by which current/future experiment. This is done for various values of currently allowed non-unitarity parameter. This comparative study will help us to pinpoint that which of the low scale seesaw models and triplet flavon VEV alignments will be more viable and favourable for testing under a common flavour symmetry ($A_{4}$ here), and hence can help discriminate between the two models.Comment: 24 pages, 6 figure

Octant of θ23\theta_{23}, MH, 0νββ0\nu\beta\beta decay and vacuum alignment of A4 A_{4} flavour symmetry in an inverse seesaw model

Measurements of disappearance channel of long baseline accelerator based experiments (like NO$\nu$A) are inflicted with the problem of octant degeneracy. In these experiments, the mass hierarchy (MH) sensitivity depends upon the value of CP-violating phase $\delta_{CP}$. Moreover, MH of light neutrino masses is still not fixed. Also, the flavour structure of fermions is yet not fully understood. We discuss all these issues, in a highly predictive, low-scale inverse seesaw (ISS) model within the framework of $A_4$ flavour symmetry. Recent global analysis has shown a preference for normal hierarchy and higher octant of $\theta_{23}$, and hence we discuss our results with reference to these, and find that the vacuum alignment of $A_4$ triplet flavon (1,-1,-1) favours these results. Finally, we check if our very precise prediction on $m_{ee}$ and the lightest neutrino mass falls within the range of sensitivities of the neutrinoless double beta decay ($0\nu\beta\beta$) experiments. We note that when octant of $\theta_{23}$ and MH is fixed by more precise measurements of future experiments, then through our results, it would be possible to precisely identify the favourable vacuum alignment corresponding to the $A_{4}$ triplet field as predicted in our model.Comment: 24 pages, 5 figure

Resolving Octant Degeneracy at LBL experiment by combining Daya Bay Reactor Setup

Long baseline Experiment (LBL) have promised to be a very powerful experimental set up to study various issues related to Neutrinos. Some ongoing and planned LBL and medium baseline experiments are - T2K, MINOS, NOvA, LBNE, LBNO etc. But the long baseline experiments are crippled due to presence of some parameter degeneracies, like the Octant degeneracy. In this work, we first show the presence of Octant degeneracy in LBL experiments, and then combine it with Daya Bay Reactor experiment, at different values of CP violation phase. We show that the Octant degeneracy in LBNE can be resolved completely with this proposal.Comment: 4 pages, 8 figure