Scalar Dark Matter with Type II Seesaw

We study the possibility of generating tiny neutrino mass through a combination of type I and type II seesaw mechanism within the framework of an abelian extension of standard model. The model also provides a naturally stable dark matter candidate in terms of the lightest neutral component of a scalar doublet. We compute the relic abundance of such a dark matter candidate and also point out how the strength of type II seesaw term can affect the relic abundance of dark matter. Such a model which connects neutrino mass and dark matter abundance has the potential of being verified or ruled out in the ongoing neutrino, dark matter as well as accelerator experiments.Comment: v2: 19 pages, 6 figures, to appear in Nucl. Phys.

Galileogenesis: A new cosmophenomenological zip code for reheating through R-parity violating coupling

In this paper we introduce an idea of leptogenesis scenario in higher derivative gravity induced DBI Galileon framework {\it aka Galileogenesis} in presence of one-loop R-parity violating couplings in the background of a low energy effective supergravity setup. We have studied extensively the detailed feature of reheating constraints and the cosmophenomenological consequences of thermal gravitino dark matter in light of PLANCK and PDG data. Finally we have also established a direct cosmological connection among dark matter relic abundance, reheating temperature and tensor-to-scalar ratio in the context of DBI Galileon inflation.Comment: 8 pages, 2 figures, Revision accepted by Nuclear Physics

Galactic Center Gamma Ray Excess in a Radiative Neutrino Mass Model

The Fermi gamma ray space telescope data have pointed towards an excess of gamma rays with a peak around $1-3$ GeV in the region surrounding the galactic center. This anomalous excess can be described well by a dark matter candidate having mass in the range $31-40$ GeV annihilating into $b\bar{b}$ pairs with a cross section of $\simeq (1.4-2.0) \times 10^{-26} \; \text{cm}^3/\text{s}$. In this work we explore the possibility of having such a dark matter candidate within the framework of a radiative neutrino mass model. The model is a simple extension of the standard model by an additional $U(1)_X$ gauge symmetry where the standard model neutrino masses arise both at tree level as well as radiatively by the anomaly free addition of one singlet fermion $N_R$ and two triplet fermions $\Sigma_{1R}, \Sigma_{2R}$ with suitable Higgs scalars. The spontaneous gauge symmetry breaking is achieved in such a way which results in a residual $Z_2$ symmetry and hence providing a stable cold dark matter candidate. We show that the singlet fermionic dark matter candidate in our model can give rise to the galactic center gamma ray excess. The parameter space which simultaneously satisfy the constraints on relic density, direct detection scattering as well as collider bounds essentially corresponds to an s-wave resonance where the gauge boson mass $m_X$ is approximately twice that of dark matter mass $m_{\chi}$. We also discuss the compatibility of such a light fermion singlet dark matter with light neutrino mass.Comment: version 2: 18 pages, 6 figures, to appear in Physics Letters

Neutrinoless Double Beta Decay in Type I+II Seesaw Models

We study neutrinoless double beta decay in left-right symmetric extension of the standard model with type I and type II seesaw origin of neutrino masses. Due to the enhanced gauge symmetry as well as extended scalar sector, there are several new physics sources of neutrinoless double beta decay in this model. Ignoring the left-right gauge boson mixing and heavy-light neutrino mixing, we first compute the contributions to neutrinoless double beta decay for type I and type II dominant seesaw separately and compare with the standard light neutrino contributions. We then repeat the exercise by considering the presence of both type I and type II seesaw, having non-negligible contributions to light neutrino masses and show the difference in results from individual seesaw cases. Assuming the new gauge bosons and scalars to be around a TeV, we constrain different parameters of the model including both heavy and light neutrino masses from the requirement of keeping the new physics contribution to neutrinoless double beta decay amplitude below the upper limit set by the GERDA experiment and also satisfying bounds from lepton flavor violation, cosmology and colliders.Comment: v2: 30 pages, 14 figures, Accepted for publication in JHE

Charged Lepton Flavour Violation and Neutrinoless Double Beta Decay in Left-Right Symmetric Models with Type I+II Seesaw

We study the new physics contributions to neutrinoless double beta decay ($0\nu\beta \beta$) half-life and lepton flavour violation (LFV) amplitude within the framework of the minimal left-right symmetric model (MLRSM). Considering all possible new physics contributions to $0\nu\beta \beta$ and charged lepton flavour violation $\mu \rightarrow e \gamma, \mu \rightarrow 3e$ in MLRSM, we constrain the parameter space of the model from the requirement of satisfying existing experimental bounds. Assuming the breaking scale of the left-right symmetry to be $\mathcal{O}(1)$ TeV accessible at ongoing and near future collider experiments, we consider the most general type I+II seesaw mechanism for the origin of tiny neutrino masses. Choosing the relative contribution of the type II seesaw term allows us to calculate the right handed neutrino mass matrix as well as Dirac neutrino mass matrix as a function of the model parameters, required for the calculation of $0\nu\beta \beta$ and LFV amplitudes. We show that such a general type I+II seesaw structure results in more allowed parameter space compared to individual type I or type II seesaw cases considered in earlier works. In particular, we show that the doubly charged scalar masses $M_{\Delta}$ are allowed to be smaller than the heaviest right handed neutrino mass $M_N$ from the present experimental bounds in these scenarios which is in contrast to earlier results with individual type I or type II seesaw showing $M_{\Delta} > M_N$.Comment: 23 pages and 21 figures. minor revision, to appear in JHEP. arXiv admin note: text overlap with arXiv:1509.0180