arXiv subjects

Joy Ganguly

Publications and source records attributed to Joy Ganguly.

7 recordsLinked to original sources

arXiv2025

Two-sector leptogenesis in a two-Higgs-doublet model with spontaneous CP violation

The extension of the Standard Model (SM) field content with one inert Higgs doublet (IHD) and three right-handed neutrinos (RHNs) is a well-motivated approach. The key advantages of the model include the appearance of a weakly interacting massive particle (WIMP) like dark matter (DM) candidate from the neutral component of the IHD, along with the plausible explanation of the sub-eV mass range of SM neutrinos via the radiative seesaw mechanism. Additionally, the decay of RHNs can contextualize the baryon asymmetry of the universe via leptogenesis and is intricately connected to CP violation. Also, given the ongoing searches for light scalars at various experimental facilities, the extended Higgs sector of the model continues to be at the forefront. However, this scotogenic framework encounters a deficiency in providing the observed amount of relic density for a particular mass range $\sim (80 - 500) $ GeV of its DM candidate, hence requiring further augmentation. Also, the WIMP scenarios have not yet resulted in conclusive hints at the direct detection experiments. In this context, our work is based on further extension of the above Scotogenic model by a dark sector. Additionally, considering the cosmic coincidence aspect, we operate within the framework of two-sector leptogenesis. To have a predictive flavor structure in the visible sector, we impose $A_4$ symmetry. Also, we adhere to spontaneous CP violation via complex vacuum expectation value of the falvon field, leading to a situation where there is only one CP-violating phase as a common connection between the visible and dark sectors. In our analysis, we find for the lightest RHN mass $\sim 10^{10}$ GeV, our results are in good agreement with the observational ratio of relic densities, i.e., $Ω_{\rm DM}/Ω_{\rm b} \sim 5$ for a few GeV range of mass of the dark sector DM candidate.

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arXiv2024

Phenomenology of the flavor symmetric scoto-seesaw model with dark matter and TM$_1$ mixing

We propose a hybrid scoto-seesaw model based on the $A_4$ non-Abelian discrete flavor symmetry. Light neutrino masses come from the tree-level type-I seesaw mechanism and from the one-loop scotogenic contribution accommodating viable dark matter candidates responsible for observed relic abundance of dark matter (DM). Respectively, both these contributions restore the atmospheric and solar neutrino mass scales. With only one right-handed neutrino, the model features specific predictions with the normal ordering of light neutrino masses, the lightest neutrino being massless, and only one relevant CP Majorana phase. The flavor symmetric setup helps us to realize the TM$_1$ mixing scheme with concrete correlations and constraints on the mixing angles and associated CP phases. The framework predicts the atmospheric mixing angle to be in the upper octant with specific ranges $0.531 (0.580) \leq \sin^2θ_{23}\leq 0.544 (0.595)$ and the Dirac CP phase is restricted within the range $\pm(1.44-1.12)$ radian. The Majorana phase is also tightly constrained with a range of $0.82-0.95$ and $1.58-1.67$ radian, which is otherwise unconstrained from neutrino oscillations. Strict predictions on the Majorana phases also yield an accurate prediction for the effective mass parameter for neutrinoless double beta within the range of $1.61-3.85$ meV. The model offers a rich phenomenology regarding DM relic density and direct search constraints, and the fermionic DM scenario has been discussed in detail, estimating its possible connection with the neutrino sector. As an example of the model studies at colliders, the SM Higgs in the diphoton decay channel is examined. The model predicts strictly vanishing $τ\to eγ$, $τ\rightarrow 3e$ decays and testable signals by MEG-II and SINDRUM/Mu3e experiments for the $μ\to e γ$ and $μ\to 3 e$ decays, respectively.

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arXiv2023

Exploring maverick top partner decays at the LHC

In this work, we have considered an extension of the standard model (SM) with a $SU(2)_L$ singlet vectorlike quark (VLQ) with electric charge $Q=+2/3$. The model also contains an additional local $U(1)_d$ symmetry group and the corresponding gauge boson is the dark photon. The VLQ is charged while all the SM particles are neutral under the new $U(1)_d$ gauge group. Even though in this model the VLQ possesses many properties qualitatively similar to that of the traditional top partner ($T_p$), there are some compelling differences as well. In particular, its branching ratio to the traditional modes ($T_p \to bW, tZ, th$) are suppressed which in turn helps to evade many of the existing bound, mainly coming from the LHC experiments. In an earlier work, such a VLQ is referred to as ``maverick top partner". It has been shown that the top partner in this model predominantly decays to a top quark and a dark photon/dark higgs pair ($T_p \to tγ_d ,~th_d$) over a large region of the parameter space. The dark photon can be made invisible and consequently, it gives rise to the missing transverse energy ($\not\!\!{E} _{T}$) signature at the LHC detector. We have mainly focused on the LHC signatures and future prospects of such top partners. In particular, we have studied the $t\bar{t}+\not\!\!{E}_{T}$ and $t+\not\!\!{E}_{T}$ signatures in the context of the LHC via pair and single productions of the top partner, respectively at 13 and 14 TeV LHC center of mass energies assuming that the dark photon either decays into an invisible mode or it is invisible at the length scale of the detector. We have shown that one can exclude $\sinθ_L \sim 0.025$ (0.05) for $m_{_{T_p}} \leq $ 2.0 (2.6) TeV at $\sqrt{s}=14$ TeV with an integrated luminosity of 3 ab$^{-1}$ using the single top partner production channel.

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arXiv2022

Common origin of $θ_{13}$ and dark matter within the flavor symmetric scoto-seesaw framework

To understand the observed pattern of neutrino masses and mixing as well as to account for the dark matter we propose a hybrid scoto-seesaw model based on the $A_4$ discrete flavor symmetry. In this setup, including at least two heavy right-handed neutrinos is essential to employ the discrete flavor symmetry that mimics once popular tribimaximal neutrino mixing at the leading order via type-I seesaw. The scotogenic contribution then acts as a critical deviation to reproduce the observed value of the reactor mixing angle $θ_{13}$ (within the trimaximal mixing scheme) and to accommodate potential dark matter candidates, pointing towards a common origin of $θ_{13}$ and dark matter. The model predicts the atmospheric angle to be in the upper octant, excludes some regions on the Dirac CP phase, and restricts the Majorana phases too. Further, normal and inverted mass hierarchies can be distinguished for specific values of the relative phases associated with the complex light neutrino mass matrix. Owing to the considered flavor symmetry, contributions coming from the scotogenic mechanism towards the lepton flavor violating decays such as $μ\rightarrow e γ$, $τ\rightarrow e γ$ vanish, and a lower limit on the second right-handed neutrino mass can be obtained. Prediction for the effective mass parameter appearing in the neutrinoless double beta decay falls within the sensitivity of future experiments such as LEGEND-1k and nEXO.

hep-ph↗

arXiv2022

Lepton and quark mixing patterns with generalized CP transformations

In this work, we have modified a scenario, originally proposed by Grimus and Lavoura, in order to obtain maximal values for atmospheric mixing angle and CP violating Dirac phase of the lepton sector. To achieve this, we have employed CP and some discrete symmetries in a type II seesaw model. In order to make predictions about neutrino mass ordering and the smallness of the reactor angle, we have obtained some conditions on the elements of the neutrino mass matrix of our model. Finally, within the framework of our model, we have studied quark masses and mixing pattern.

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arXiv2022

Fermion mass hierarchy and lepton flavor violation using $CP$ symmetry

We present a model which employs $CP\times Z_3$ symmetries where quark mixing and charged leptons masses are explained by following some texture. To achieve neutrino mass and mixing, we write a non-renormalizable Lagrangian using type-II seesaw mechanism by assuming ${\mathcal{O}}(1)$ couplings predicting no $CP$ violation. Then, we calculate the value of the couplings for both normal and inverted ordering of neutrino masses. We propose a mechanism of ultra-violet (UV) completion that motivates the higher dimensional Lagrangian in the neutrino sector. We also calculate the branching fraction of lepton flavor violating decays driven by triplet scalar for the model. Later, it is shown that the model can also accommodate maximal $CP$ violation by breaking the $CP$ symmetry spontaneously.

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arXiv2021

Neutrino Mixing by modifying the Yukawa coupling structure of constrained sequential dominance

In the constrained sequential dominance (CSD), tri-bimaximal mixing (TBM) pattern in the neutrino sector has been explained, by proposing a certain Yukawa coupling structure for the right-handed neutrinos of the model. However, from the current experimental data it is known that the values of neutrino mixing angles are deviated from the TBM values. In order to explain this neutrino mixing, we first propose a phenomenological model where we consider Yukawa couplings which are modified from that of CSD. Essentially, we add small complex parameters to the Yukawa couplings of CSD. Using these modified Yukawa couplings, we demonstrate that neutrino mixing angles can deviate from their TBM values. We also construct a model, based on a flavor symmetry, in order to justify the modified form of Yukawa couplings of our work.

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