Weekly seminars
125 GeV Higgs, Vacuum Stability and Dark matter in the Type-II Seesaw model
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Europe/Paris
Auditorium (Annecy-le-Vieux)
Auditorium
Annecy-le-Vieux
Description
We 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. For any given enhancement in the Higgs-to-diphoton rate over its SM expectation, there exists an upperbound 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. Addition of an extra singlet scalar fi eld to this model can play the role of cold dark matter (DM). This DM candidate is leptophilic for a wide range of model parameter space, and the lepton flux due to its annihilation carries information about the neutrino mass hierarchy. Using the recently released high precision data on positron fraction and flux from the AMS-02 experiment, we examine the DM interpretation of the observed positron excess in our model. We find that a good fit to the AMS-02 data can be obtained with a normal hierarchy of neutrino masses, while the inverted hierarchy case is somewhat disfavored. This is consistent with the current upper limits derived from Fermi-LAT and IceCube data. Moreover, the absence of an excess anti-proton flux as suggested by PAMELA data sets an indirect upper limit on the DM-nucleon 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.