Narrow Results

We study the possibility of explaining the recently reported 750 GeV di-photon excess at LHC within the framework of a left–right symmetric model. The 750 GeV neutral scalar in the model is dominantly an admixture of neutral components of scalar bidoublets with a tiny fraction of neutral scalar triplet. Incorporating $SU(2)$ septuplet scalar pairs into the model, we enhance the partial decay width of the 750 GeV neutral scalar into di-photons through charged septuplet components in loop while keeping the neutral septuplet components as subdominant dark matter candidates. The model also predicts the decay width of the 750 GeV scalar to be around 36 GeV to be either confirmed or ruled out by future LHC data. The requirement of producing the correct di-photon signal automatically keeps the septuplet dark matter abundance subdominant in agreement with bounds from direct and indirect detection experiments. We then briefly discuss different possibilities to account for the remaining dark matter component of the Universe in terms of other particle candidates whose stability arises either due to remnant discrete symmetry after spontaneous breaking of $U{(1)}_{B-L}$ or due to high $SU(2)$-dimension forbidding their decay into lighter particles.

We construct a minimal calculable model of a light dilaton based on the scenario where only top and Higgs sectors are involved in a quasi scale invariant dynamics. The model consistently accommodate the electroweak precision tests even when the Higgs boson is very heavy, thereby allows one to consider a possibility that the particle at around 125 GeV, discovered at the LHC experiments, is identified as the light dilaton rather than the Higgs boson. We find that the current LHC data allow distinct parameter regions where the observed particle is either mostly the Higgs boson or the dilaton.