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Register a new userExplaining 750 GeV diphoton excess from top/bottom partner cascade decay in two-Higgs-doublet model extension
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In this paper, we interpret the 750 GeV diphoton excess in the Zee-Babu extension of the two-Higgs-doublet model by introducing a top partner ($T$)/bottom partner ($B$). In the alignment limit, the 750 GeV resonance is identified as the heavy CP-even Higgs boson ($H$), which can be sizably produced via the QCD process $pp to Tbar{T}$ or $pp to Bbar{B}$ followed by the decay $Tto Ht$ or $B to Hb$. The diphoton decay rate of $H$ is greatly enhanced by the charged singlet scalars predicted in the Zee-Babu extension and the total width of $H$ can be as large as 7 GeV. Under the current LHC constraints, we scan the parameter space and find that such an extension can account for the observed diphoton excess.
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In the E6 inspired composite Higgs model (E6CHM) the strongly interacting sector possesses an SU(6)times U(1)_Btimes U(1)_L global symmetry. Near scale fgtrsim 10 TeV the SU(6) symmetry is broken down to its SU(5) subgroup, that involves the standard model (SM) gauge group. This breakdown of SU(6) leads to a set of pseudo--Nambu--Goldstone bosons (pNGBs) including a SM--like Higgs and a SM singlet pseudoscalar A. Because of the interactions between A and exotic fermions, which ensure the approximate unification of the SM gauge couplings and anomaly cancellation in this model, the couplings of the pseudoscalar A to gauge bosons get induced. As a result, the SM singlet pNGB state A with mass around 750 GeV may give rise to sufficiently large cross section of ppto gammagamma that can be identified with the recently observed diphoton excess.
In this paper we simultaneously explain the excesses of the 750 GeV diphoton, muon g-2 and $hto mutau$ in an extension of the two-Higgs-doublet model (2HDM) with additional vector-like fermions and a CP-odd scalar singlet ($P$) which is identified as the 750 GeV resonance. This 750 GeV resonance has a mixing with the CP-odd scalar ($A$) in 2HDM, which leads to a coupling between $P$ and the SM particles as well as a coupling between $A$ and the vector-like fermions. Such a mixing and couplings are strongly constrained by $tautomugamma$, muon g-2 and the 750 GeV diphoton data. We scan over the parameter space and find that such an extension can simultaneously account for the observed excesses of 750 GeV diphoton, muon g-2 and $hto mutau$. The 750 GeV resonance decays in exotic modes, such as $Pto hA$, $Pto HZ$, $Pto HA$ and $Pto W^pm H^mp$, and its width can be dozens of GeV and is sensitive to the mixing angle.
We study kinematic distributions that may help characterise the recently observed excess in diphoton events at 750 GeV at the LHC Run 2. Several scenarios are considered, including spin-0 and spin-2 750 GeV resonances that decay directly into photon pairs as well as heavier parent resonances that undergo three-body or cascade decays. We find that combinations of the distributions of the diphoton system and the leading photon can distinguish the topology and mass spectra of the different scenarios, while patterns of QCD radiation can help differentiate the production mechanisms. Moreover, missing energy is a powerful discriminator for the heavy parent scenarios if they involve (effectively) invisible particles. While our study concentrates on the current excess at 750 GeV, the analysis is general and can also be useful for characterising other potential diphoton signals in the future.
We examine the implication of the 750 GeV diphoton resonance on the two-Higgs-doublet model imposing various theoretical and experimental constraints. The production rate of two-Higgs-doublet model is smaller than the cross section observed at the LHC by two order magnitude. In order to accommodate the 750 GeV diphoton resonance, we extend the two-Higgs-doublet model by introducing additional Higgs fields, and focus on two different extensions, an inert complex Higgs triplet and a real scalar septuplet. With the 125 GeV Higgs being agreement with the observed data, the production rate for the 750 GeV diphoton resonance can be enhanced to 0.6 fb for the former and 4.5 fb for the latter. The results of the latter are well consistent with the 750 GeV diphoton excess at the LHC.
We investigate a possibility for explaining the recently announced 750,GeV diphoton excess by the ATLAS and the CMS experiments at the CERN LHC in a model with multiple doubly charged particles, which was originally suggested for explaining tiny neutrino masses through a three-loop effect in a natural way. The enhanced radiatively generated effective coupling of a new singlet scalar $S$ with diphoton with multiple charged particles in the loop enlarges the production rate of $S$ in $ppto S+X$ via photon fusion process and also the decay width $Gamma(Sto gammagamma)$ even without assuming a tree level production mechanism. We provide detailed analysis on the cases with or without allowing the mixing between $S$ and the standard model Higgs doublet.
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