arXiv subjects

Arunansu Sil

Publications and source records attributed to Arunansu Sil.

54 records · Page 3Linked to original sources

arXiv2016

Unifying the flavor origin of dark matter with leptonic nonzero $θ_{13}$

We propose a flavor symmetric approach to unify the origin of dark matter (DM) with the non-zero $θ_{13}$ in the lepton sector. In this framework, breaking of a $U(1)$ flavor symmetry to a remnant $Z_2$ ensures the stability of the DM and gives rise to a modification to the existing $A_4$-based tri-bimaximal neutrino mixing to attain the required non-zero $\sin θ_{13}$. This results in a range of Higgs portal coupling of the DM which can be potentially accessible at various ongoing and future direct and collider search experiments.

hep-ph↗

arXiv2015

A Dynamic Modification to Sneutrino Chaotic Inflation

We consider a right-handed scalar neutrino as the inflaton which carries a gravitational coupling with a supersymmetric QCD sector responsible for breaking supersymmetry dynamically. The framework suggests an inflaton potential which is a deformed version of the quadratic chaotic inflation leading to a flatter potential. We find that this deformation results a sizable tensor to scalar ratio which falls within the allowed region by PLANCK 2015. At the same time supersymmetry breaking at the end of inflation can naturally be induced in this set-up. The symmetries required to construct the framework allows the neutrino masses and mixing to be of right order.

hep-ph↗

arXiv2015

Spontaneous CP Violation in Lepton-sector: a common origin for $θ_{13}$, Dirac CP phase and leptogenesis

A possible interplay between the two terms of the general type-II seesaw formula is exercised which leads to the generation of nonzero $θ_{13}$. The specific flavor structure of the model, guided by the $A_4 \times Z_4 \times Z_3$ symmetry and accompanied with the Standard Model singlet flavons, yields the conventional seesaw contribution to produce the tribimaximal lepton mixing which is further corrected by the presence of the $SU(2)_L$ triplet contribution to accommodate $θ_{13}$. We consider the CP symmetry to be spontaneously broken by the complex vacuum expectation value (vev) of a singlet field $S$. While the magnitude of its complex vev is responsible for generating $θ_{13}$, its phase part induces the low energy CP violating phase ($δ$) and the CP violation required for leptogenesis. Hence the triplet contribution, although sub-dominant, plays crucial role in providing a common source for non-zero $θ_{13}$, $δ$ and CP-violation required for leptogenesis. We find that the recent hint for $δ$ close to $3π/2$ is somewhat favored in this set-up though it excludes the exact equality with $3π/2$. We also discuss the generation of lepton asymmetry in this scenario.

hep-ph↗

arXiv2015

Nonzero $θ_{13}$ and Leptogenesis in a Type-I See-saw Model with $A_4$ Symmetry

In the light of recent discovery of nonzero $θ_{13}$, we have analyzed the Altarelli-Feruglio $A_4$ flavor symmetry model extended with additional flavon. The inclusion of the new field leads to the deviation from exact tri-bimaximal neutrino mixing pattern in the context of type-I see-saw by producing a nonzero $θ_{13}$ consistent with the recent experimental results at the leading order. A sum rule for light neutrino masses is also obtained in this context. The set-up constraints the two Majorana phases involved in the lepton mixing matrix in terms of $A_4$ parameter space. We have shown that a nonzero lepton asymmetry can be generated while next-to-leading order contributions to the neutrino Yukawa couplings are considered. The two Majorana phases play crucial role in CP-asymmetry parameter and the involvement of $θ_{13}$ in it, is exercised.

hep-ph↗

arXiv2015

Warm Dark Matter in B-L Inverse Seesaw

We show that a standard model gauge singlet fermion field, with mass of order keV or larger, and involved in the inverse seesaw mechanism of light neutrino mass generation, can be a good warm dark matter candidate. Our framework is based on B-L extension of the Standard Model. The construction ensures the absence of any mixing between active neutrinos and the aforementioned dark matter field. This circumvents the usual constraints on the mass of warm dark matter imposed by X-ray observations. We show that over-abundance of thermally produced warm dark matter (which nevertheless do not reach chemical equilibrium) can be reduced to an acceptable range in the presence of a moduli field decaying into radiation --- though only when the reheat temperature is low enough. Our warm dark matter candidate can also be produced directly from the decay of the moduli field during reheating. In this case, obtaining the right amount of relic abundance, while keeping the reheat temperature high enough as to be consistent with Big Bang nucleosynthesis bounds, places constraints on the branching ratio for the decay of the moduli field into dark matter.

hep-ph↗

arXiv2013

Two Component Dark Matter : A Possible Explanation of 130 GeV γ-Ray Line from the Galactic Centre

Recently there has been a hint of a gamma-ray line at 130 GeV originated from the galactic centre after the analysis of the Fermi-LAT satellite data. Being monochromatic in nature, it rules out the possibility of having its astrophysical origin and there has been a speculation that this line could be originated from dark matter annihilation. In this work, we propose a two component dark matter scenario where an extension of the Standard model by an inert Higgs doublet and a gauge singlet scalar concocted with $\rm {Z_2 \times Z^{\prime}_2}$ symmetry, is considered. We find that our scenario can not only explain the 130 GeV gamma-ray line through dark matter annihilation but also produce the correct dark matter relic density. We have used the Standard Model Higgs mass around 125 GeV as intimated by the LHC data..

hep-ph↗

arXiv2012

Smooth Hybrid Inflation and Non-Thermal Type II Leptogenesis

We consider a smooth hybrid inflation scenario based on a supersymmetric SU(2)_L x SU(2)_R x U(1)_B-L model. The Higgs triplets involved in the model play a key role in inflation as well as in explaining the observed baryon asymmetry of the universe. We show that the baryon asymmetry can originate via non-thermal triplet leptogenesis from the decay of SU(2)_L triplets, whose tiny vacuum expectation values also provide masses for the light neutrinos.

hep-ph↗

arXiv2011

Right-handed Sneutrino Inflation in SUSY B-L with Inverse Seesaw

We propose a scenario for realizing inflation in the framework of supersymmetric B-L extension of the Standard Model. We find that one of the associated right-handed sneutrinos (the superpartner of the Standard Model singlet fermion) can provide a new non-trivial inflationary trajectory at tree level (therefore breaking B-L during inflation). As soon as the inflation ends, the right-handed sneutrino falls into the supersymmetric vacuum, with a vanishing vacuum expectation value, so that B-L symmetry is restored. In this class of models, the B-L gauge symmetry will be radiatively broken at a TeV scale and light neutrino masses are generated through the inverse seesaw mechanism.

hep-ph↗

arXiv2009

SQCD Inflation & SUSY Breaking

A model of generalised hybrid inflation in a supersymmetric QCD theory is proposed whose parameters are the gauge coupling and quark masses. Its gravitational coupling to another SQCD sector induces a metastable supersymmetry breaking vacuum of the ISS type as ISS quarks become massive at the end of inflation. Using a known mechanism with a gravitational breaking of the baryon number and the gauging of flavour symmetries, we find that gauge mediation of supersymmetry breaking is compatible with the dynamics of the inflation sector. Reheating proceeds via the thermalization of the ISS messengers into the standard model states. This setup contains a single dimensionful parameter in the form of a quark mass term in the inflationary sector, i.e. all other scales involved are either related to this single mass parameter or dynamically generated.

hep-ph↗

arXiv2008

Intermediate Scale Inflation and Metastable Supersymmetry Breaking

We investigate the possibility of obtaining a low scale of supersymmetry breaking within the ISS framework using a metastable vacuum. This is achieved by introducing an R-symmetry preserving gravitational coupling of the ISS sector to a relatively low scale inflationary sector. We find the allowed range for the supersymmetry breaking scale, 10^4 GeV < μ< 10^8 GeV, which is low enough to be amenable to gauge supersymmetry breaking mediation. This scenario is based upon a so-called hilltop inflation phase whose initial condition problem is also addressed.

hep-ph↗

arXiv2008

Can Inflation Induce Supersymmetry Breaking in a Metastable Vacuum?

We argue that fields responsible for inflation and supersymmetry breaking are connected by gravitational couplings. In view of the recent progress in studying supersymmetry breaking in a metastable vacuum, we have shown that in models of supersymmetric hybrid inflation, where R-symmetry plays an important role, the scale of supersymmetry breaking is generated dynamically at the end of inflation and turns out to be consistent with gravity mediation.

hep-ph↗

arXiv2006

Flux of Primordial Monopoles

We discuss how in supersymmetric models with D and F-flat directions, a primordial monopole flux of order 10^{-16} - 10^{-18} cm^{-2} sec^{-1} sr^{-1} can coexist with the observed baryon asymmetry. A modified Affleck-Dine scenario yields the desired asymmetry if the monopoles are superheavy (~ 10^{13}-10^{18} GeV). For lighter monopoles with masses ~ 10^{9}-10^{12} GeV, the baryon asymmetry can arise via TeV scale leptogenesis.

hep-ph↗

arXiv2006

TeV Scale Leptogenesis, theta_13 And Doubly Charged Particles At LHC

We explore a realistic supersymmetric SU(2)_L \times SU(2)_R \times U(1)_B-L model spontaneously broken at around 10^12 GeV. The presence of D and F-flat directions gives rise to TeV mass doubly charged particles which can be found at the LHC. We implement TeV scale leptogenesis and employing both type I and II seesaw, the three light neutrinos are partially degenerate with masses in the 0.02-0.1 eV range. The effective mass parameter for neutrinoless double beta decay is 0.03-0.05 eV. We also find the interesting relation tan 2 θ_13 ~ [Δm^2_{\odot} / Δm^2_{atm}] [sin 2 θ_12 /tan 2 θ_23] <~ 0.02.

hep-ph↗

arXiv2005

Hybrid Inflation, Dark Energy And Dark Matter

It has been suggested that the dark energy density ρ_v ~ 10^{-12} eV^4 in the universe is associated with a metastable (false) vacuum, while the true vacuum has a vanishing cosmological constant. By including supergravity corrections we show how this is naturally realized in realistic supersymmetric hybrid inflation models. With a fundamental supersymmetry breaking scale ~ TeV, the LSP is not a suitable candidate for cold dark matter. We consider axion physics to overcome this and simultaneously provide a resolution of the MSSM μproblem.

hep-ph↗

arXiv2003

Can radiative magnification of mixing angles occur for two-zero neutrino mass matrix textures?

Neutrino Majorana masses and mixings can be generated from a dimension-5 operator within the standard model particle content. After a review of the mechanism of radiative enhancement of the mixing angle in a two-neutrino case, we consider three-flavour mass matrices of two-zero texture generated from such an operator and investigate the possibility of implementing the mechanism here. We observe that radiative magnification of only the solar angle is consistent with oscillation data on masses and mixings, and that too for nearly degenerate neutrinos, with two of them having opposite CP parities, while for hierarchical masses the mechanism does not work. In supersymmetry or in an extra-dimensional scenario the above features are qualitatively unchanged.

hep-ph↗

arXiv2001

Violation of the Equivalence Principle in the light of the SNO and SK solar neutrino results

The SNO result on charged current deuteron disintegration, the SuperKamiokande 1258-day data on electron scattering, and other solar neutrino results are used to revisit the model of neutrino oscillations driven by a violation of the equivalence principle. We use a chisq minimization technique to examine oscillation between the nu(e) and another active neutrino, both massless, and find that within the Standard Solar Model the fit to the SNO and SuperKamiokande spectra are moderately good while a very good fit is obtained when the absolute normalizations of the 8B and hep neutrino fluxes are allowed to vary. The best fit prefers large, but not maximal, mixing, essentially no hep neutrinos, and a 40% reduction in the 8B neutrino flux. The fit to the total rates from the different experiments is not encouraging but when the rates and spectra are considerd together the situation is much improved. We remark on the expectations of the VEP model for the neutral current measurements at SNO.

hep-ph↗

arXiv2001

A new three flavor oscillation solution of the solar neutrino deficit in R-parity violating supersymmetry

We present a solution of the solar neutrino deficit using three flavors of neutrinos within the R-parity non-conserving supersymmetric model. In vacuum, mass and mixing is restricted to the nu(mu)-nu(tau) sector only, which we choose in consistency with the requirements of the atmospheric neutrino anomaly. The nu(e) is massless and unmixed. The flavor changing and flavor diagonal neutral currents present in the model and an energy-dependent resonance-induced nu(e)-nu(mu) mixing in the sun result in the new solution to the solar neutrino problem. The best fit to the solar neutrino rates and spectrum (1258-day SK data) requires a mass square difference of 10^{-5} eV^2 in vacuum between the two lightest neutrinos. This solution cannot accommodate a significant day-night effect for solar neutrinos.

hep-ph↗

arXiv2001

Solar neutrino results and Violation of the Equivalence Principle: An analysis of the existing data and predictions for SNO

Violation of the Equivalence Principle (VEP) can lead to neutrino oscillation through the non-diagonal coupling of neutrino flavor eigenstates with the gravitational field. The neutrino energy dependence of this oscillation probability is different from that of the usual mass-mixing neutrino oscillations. In this work we explore, in detail, the viability of the VEP hypothesis as a solution to the solar neutrino problem in a two generation scenario with both the active and sterile neutrino alternatives, choosing these states to be massless. To obtain the best-fit values of the oscillation parameters we perform a chi square analysis for the total rates of solar neutrinos seen at the Chlorine (Homestake), Gallium (Gallex and SAGE), Kamiokande, and SuperKamiokande (SK) experiments. We find that the goodness of these fits is never satisfactory. It markedly improves, especially for VEP transformation to sterile neutrinos, if the Chlorine result is excluded from the analysis. The 1117-day SK data for recoil electron spectrum are also examined for signals of VEP oscillations. For these fits, we consider variations of the Standard Solar Model by allowing the absolute normalizations of the 8B and hep neutrinos to vary. Here the fits are quite good but the best fit values of the parameters are rather different from those from the total rates fits. A combined fit to the total rates and recoil electron spectrum data is also performed. We present the 90% confidence limit contours for all the three analyses mentioned above. The best-fit parameters obtained from the recoil electron spectrum and the combined analysis of rate and spectrum are used to predict the charge current and scattering electron spectrum at SNO.

hep-ph↗