arXiv subjects

Arnab Dasgupta

Publications and source records attributed to Arnab Dasgupta.

66 records · Page 4Linked to original sources

arXiv2015

Minimal Left-Right Symmetry Confronted with the 750 GeV Di-photon Excess at LHC

The recent results of 13 TeV ATLAS and CMS di-photon searches show an excess at di-photon invariant mass of 750 GeV. We look for possible explanation of this within minimal left right symmetric model (MLRSM). The possible candidate is a neutral Higgs of mass 750 GeV that can decay to di-photon via charged Higgs and right handed gauge boson loop. However, the cross-section is not consistent with the ATLAS and CMS results. We then discuss one possible variation of this model with universal seesaw for fermion masses that can explain this excess.

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arXiv2015

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.

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arXiv2015

Common Origin of 3.55 keV X-Ray Line and Galactic Center Gamma Ray Excess in a Radiative Neutrino Mass Model

We attempt to simultaneously explain the recently observed 3.55 keV X-ray line in the analysis of XMM-Newton telescope data and the galactic center gamma ray excess observed by the Fermi gamma ray space telescope within an abelian gauge extension of standard model. We consider a two component dark matter scenario with tree level mass difference 3.55 keV such that the heavier one can decay into the lighter one and a photon with energy 3.55 keV. The lighter dark matter candidate is protected from decaying into the standard model particles by a remnant $Z_2$ symmetry into which the abelian gauge symmetry gets spontaneously broken. If the mass of the dark matter particle is chosen to be within $31-40$ GeV, then this model can also explain the galactic center gamma ray excess if the dark matter annihilation into $b\bar{b}$ pairs has a cross section of $\langle σv \rangle \simeq (1.4-2.0) \times 10^{-26} \; \text{cm}^3/\text{s}$. We constrain the model from the requirement of producing correct dark matter relic density, 3.55 keV X-ray line flux and galactic center gamma ray excess. We also impose the bounds coming from dark matter direct detection experiments as well as collider limits on additional gauge boson mass and gauge coupling. We also briefly discuss how this model can give rise to sub-eV neutrino masses at tree level as well as one-loop level while keeping the dark matter mass at few tens of GeV. We also constrain the model parameters from the requirement of keeping the one-loop mass difference between two dark matter particles below a keV. We find that the constraints from light neutrino mass and keV mass splitting between two dark matter components show more preference for opposite $CP$ eigenvalues of the two fermion singlet dark matter candidates in the model

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arXiv2015

Nonthermal $CP$ violation in soft leptogenesis

Soft leptogenesis is a mechanism which generates the matter-antimatter asymmetry of the Universe via the out-of-equilibrium decays of heavy sneutrinos in which soft supersymmetry breaking terms play two important roles: they provide the required $CP$ violation and give rise to the mass splitting between otherwise degenerate sneutrino mass eigenstates within a single generation. This mechanism is interesting because it can be successful at the lower temperature regime $T \lesssim 10^9$ GeV in which the conflict with the overproduction of gravitinos can possibly be avoided. In earlier works, the leading $CP$ violation is found to be nonzero only if finite temperature effects are included. By considering generic soft trilinear couplings, we find two interesting consequences: (1) the leading $CP$ violation can be nonzero even at zero temperature realizing nonthermal $CP$ violation, and (2) the $CP$ violation is sufficient even far away from the resonant regime allowing soft supersymmetry breaking parameters to assume natural values at around the TeV scale. We discuss phenomenological constraints on such scenarios and conclude that the contributions to charged lepton flavor violating processes are close to the sensitivities of present and future experiments.

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arXiv2015

The Discovery reach of $CP$ violation in neutrino oscillation with non-standard interaction effects

We have studied the $CP$ violation discovery reach in neutrino oscillation experiment with superbeam, neutrino factory and monoenergetic neutrino beam. For NSI satisfying model-dependent bound for shorter baselines (like CERN-Fréjus set-up ) there is insignificant effect of NSI on the the discovery reach of $CP$ violation due to $δ$. Particularly, for superbeam and neutrino factory we have also considered relatively longer baselines for which there could be significant NSI effects on $CP$ violation discovery reach for higher allowed values of NSI. For monoenergetic beam only shorter baselines are considered to study $CP$ violation with different nuclei as neutrino sources. Interestingly for non-standard interactions - $\varepsilon_{eμ}$ and $\varepsilon_{eτ}$ of neutrinos with matter during propagation in longer baselines in superbeam, there is possibility of better discovery reach of $CP$ violation than that with only Standard Model interactions of neutrinos with matter. For complex NSI we have shown the $CP$ violation discovery reach in the plane of Dirac phase $δ$ and NSI phase $ϕ_{ij}$. The $CP$ violation due to some values of $δ$ remain unobservable with present and near future experimental facilities in superbeam and neutrino factory . However, in presence of some ranges of off-diagonal NSI phase values there are some possibilities of discovering total $CP$ violation for any $δ_{CP}$ value at $5 σ$ for neutrino factory. Our analysis indicates that for some values of NSI phases total $CP$ violation may not be at all observable for any values of $δ$. Using a neutrino beam from electron capture process for nuclei $^{110}_{50}$Sn and $^{152}$Yb, we have shown the discovery reach of $CP$ violation in neutrino oscillation experiment.

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arXiv2014

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 $< σv > \simeq (1.4-2.0) \times 10^{-26} \; \text{cm}^3/\text{s}$. 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 $Σ_{1R}, Σ_{2R}$ 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 $m_χ$. We also discuss the compatibility of such a light fermion singlet dark matter with light neutrino mass.

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arXiv2014

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.

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arXiv2014

Non-standard interaction effect on $CP$ violation in neutrino oscillation with super-beam

We have studied the $CP$ violation discovery reach in neutrino oscillation experiment with superbeam in presence of non-standard interactions of neutrinos with matter for both short and long baselines. For the most important channel of oscillation ($ν_μ\rightarrow ν_e$) for $CP$ violation discovery there is significant effect in the oscillation probability particularly due to NSIs' $\varepsilon_{eμ}$ and $\varepsilon_{eτ}$ for longer baseline and higher energy in comparison to other NSIs'. Interestingly for these two NSIs' (for real and higher allowed values) there is possibility of better discovery reach of $CP$ violation than that with only Standard Model interactions of neutrinos with matter provided that NSI values are known. For complex NSIs' we have shown the $CP$ violation discovery reach in the plane of Dirac phase $δ$ and NSI phase $ϕ_{ij}$. Our analysis indicates that for some values of some NSI phases total $CP$ violation may not be observable for any values of $δ$.

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arXiv2014

Discovery reach of $CP$ violation and non-standard interactions in low energy neutrino factory

In low energy neutrino factory ($E_μ< 10$GeV) using MIND detector, we have studied the optimization of $CP$ violation discovery reach in the leptonic sector for different baselines and different parent muon energy considering only Standard Model interactions of neutrinos with matter. Considering such optimized experimental set-up of baseline and energy we have addressed the question of how $CP$ violation discovery reach could get affected by the presence of non-standard interactions of neutrinos with matter during the propagation of neutrinos. For off diagonal NSI elements there could be complex phases $ϕ_{ij}$ which could also lead to $CP$ violation. In presence of these complex phases we have shown the contours showing the discovery reach of $δ$ and $ϕ_{ij}$. We have also shown the discovery reach of NSIs in the same experimental set-up which is optimized for discovery of $CP$ violation in the leptonic sector.

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arXiv2014

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.

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arXiv2012

Non-standard interaction in neutrino oscillations and recent Daya Bay, T2K experiments

We study the possible constraints on non-standard interaction(NSIs) in a model independent way by considering the recent results from T2K and Daya Bay neutrino oscillations experiments. Using perturbation method we present generic formulas (suitable for T2K baseline and for large $θ_{13}$ as evident from Daya Bay) for the probability of oscillation for $ν_μ\rightarrow ν_e$, taking into account NSIs at source ($ε^s$), detector ($ε^d$) and during propagation ($ε^m$) of neutrinos through matter. Two separate cases of perturbation with small (slightly large) NSI ($ε_{αβ}^m \sim 0.03(0.18)$) are discussed in detail. Using various possible presently allowed NSI values we reanalyze numerically the $θ_{13} - δ$ allowed region given by recent T2K experimental data. We obtain model independent constraints on NSIs in the $δ-ε_{αβ}^m$ plane using the $θ_{13}$ value as measured by Daya Bay, where $δ$ is the CP violating phase. Depending on $δ$ values significant constraints on $ε_{eτ}$ and $ε_{ττ}$, in particular, are possible for both hierarchies of neutrino masses. Corresponding to T2K's 66% confidence level result, the constraints on $ε_{ττ}$ is shown to be independent of any $δ$ value.

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arXiv2012

Non-standard interactions and bimagic baseline for neutrino oscillations

For standard interactions of neutrinos with matter bimagic baseline of length about 2540 Km is known to be suitable for getting good discovery limits of neutrino mass hierarchy, $\sin^2 θ_{13}$ and CP violation in the $ν_e \rightarrow ν_μ$ oscillation channel. We discuss how even in presence of non-standard interactions (NSIs) of neutrinos with matter this baseline is found to be suitable for getting these discovery limits. This is because even in presence of NSIs one could get the $ν_e \rightarrow ν_μ$ oscillation probability to be almost independent of CP violating phase $δ$ and $θ_{13}$ for one hierarchy and highly dependent on these two for the other hierarchy over certain parts of neutrino energy range. For another certain part of the energy range the reverse of this happens with respect to the hierarchies. We present the discovery limits of NSIs also in the same neutrino energy range. However, as with the increase of neutrino energy the NSI effect in the above oscillation probability gets relatively more pronounced in comparison to the vacuum oscillation parameters, so we consider higher neutrino energy range also for getting better discovery limits of NSIs. Analysis presented here for 2540 Km could also be implemented for longer bimagic baseline $> 6000$ Km.

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