Ipsita Saha

125 GeV Higgs boson and the type-II seesaw model

A bstractWe study the vacuum stability and unitarity conditions for a 125 GeV Standard Model (SM)-like Higgs boson mass in the type-II seesaw model. We find that, as long as the seesaw scale is introduced below the SM vacuum instability bound, there exists a large parameter space predicting a 125 GeV Higgs mass, irrespective of the exact value of the seesaw scale, satisfying both stability and unitarity conditions up to the Planck scale. We also study the model predictions for the Higgs partial decay widths in the diphoton and Z+photon channels with respect to their SM expectations and find that the decay rates for these two processes are anti-correlated. We further show that for any given enhancement in the Higgs-to-diphoton rate over its SM expectation, there exists an upper bound on the type-II seesaw scale, and hence, on the masses of the associated doubly- and singly-charged Higgs bosons in the allowed parameter space. For instance, if more than 10% enhancement persists in the Higgs-to-diphoton channel, the upper limit on the type-II seesaw scale is about 450 GeV which is completely within the reach of the 14 TeV LHC. We believe this to be an encouraging result for the experimental searches of the singly- and doubly-charged Higgs bosons which, in combination with improved sensitivity in the Higgs-to-diphoton and Higgs-to-Z+photon channels, could probe the entire allowed parameter space of the minimal type-II seesaw model, and establish/eliminate it as a single viable extension of the SM.

Confronting the galactic center gamma-ray excess with a light scalar dark matter

The Fermi Large Area Telescope observed an excess in gamma-ray emission spectrum coming from the center of the Milky Way galaxy. This data reveals that a light dark matter (DM) candidate of mass in the range 31?40 GeV, dominantly decaying into b final state, can explain the presence of the observed bump in photon energy. We try to interpret this observed phenomena by sneutrino DM annihilation into pair of fermions in the Supersymmetric Inverse Seesaw Model (SISM). This model can also account for tiny non-zero neutrino masses satisfying existing neutrino oscillation data. We show that a Higgs portal DM in this model is in perfect agreement with this new interpretation besides satisfying all other existing collider, cosmological and low energy experimental constraints.

Neutrino Mass and Dark Matter in light of recent AMS-02 results

We study a simple extension of the Standard Model supplemented by an electroweak triplet scalar eld to accommodate small neutrino masses by the type-II seesaw mechanism, while an additional singlet scalar eld can play the role of cold dark matter (DM) in our Universe. This DM candidate is leptophilic for a wide range of model parameter space, and the lepton ux due to its annihilation carries information about the neutrino mass hierarchy. Using the recently released high precision data on positron fraction and ux from the AMS-02 experiment, we examine the DM interpretation of the observed positron excess in our model for two kinematically distinct scenarios with the DM and triplet scalar masses (a) non-degenerate (mDM m ), and (b) quasi-degenerate (mDM’ m ). We nd that a good t to the AMS-02 data can be obtained in both cases (a) and (b) with a normal hierarchy of neutrino masses, while the inverted hierarchy case is somewhat disfavored. Although we require a larger boost factor for the normal hierarchy case, this is still consistent with the current upper limits derived from Fermi-LAT and IceCube data for case (a). Moreover, the absence of an excess anti-proton ux as suggested by PAMELA data sets an indirect upper limit on the DMnucleon spin-independent elastic scattering cross section which is stronger than the existing DM direct detection bound from LUX in the AMS-02 preferred DM mass range.

Dark matter, neutrino masses and high scale validity of an inert Higgs doublet model

We consider a two-Higgs doublet scenario containing three SU(2)L singlet heavy neutrinos with Majorana masses. The second scalar doublet as well as the neutrinos are odd under a Z2 symmetry. This scenario not only generates Majorana masses for the light neutrinos radiatively but also makes the lighter of the neutral Z2-odd scalars an eligible dark matter candidate, in addition to triggering leptogenesis at the scale of the heavy neutrino masses. Taking two representative values of this mass scale, we identify the allowed regions of the parameter space of the model, which are consistent with all dark matter constraints. At the same time, the running of quartic couplings in the scalar potential to high scales is studied, thus subjecting the regions consistent with dark matter constraints to further requirements of vacuum stability, perturbativity and unitarity. It is found that part of the parameter space is consistent with all of these requirements all the way up to the Planck scale, and also yields the correct signal strength in the diphoton channel for the scalar observed at the Large Hadron Collider.

Left-right supersymmetry after the Higgs boson discovery

We perform a thorough analysis of the parameter space of the minimal left-right supersymmetric model in agreement with the LHC data. The model contains left- and right-handed fermionic doublets, two Higgs bidoublets, two Higgs triplet representations, and one singlet, insuring a charge-conserving vacuum. We impose the condition that the model complies with the experimental constraints on supersymmetric particles masses and on the doubly-charged Higgs bosons, and require that the parameter space of the model satisfy the LHC data on neutral Higgs signal strengths at

Can measurements of 2HDM parameters provide hints for high scale supersymmetry

2\sigma

Little Higgs after the little one

. We choose benchmark scenarios by fixing some basic parameters and scanning over the rest. The LSP in our scenarios is always the lightest neutralino. We find that the signals for

Charged Higgs in Beyond the Minimal Supersymmetric Standard Model at the LHC

H\to \gamma \gamma

Dark matter and collider studies in the left-right symmetric model with vectorlike leptons

and

Distinguishing neutrino mass hierarchies using dark matter annihilation signals at IceCube

H \to VV^\star