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Register a new userImplication of the 750 GeV diphoton resonance on two-Higgs-doublet model and its extensions with Higgs field
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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.
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We revisit models where a heavy chiral 4th generation doublet of fermions is embedded in a class of two Higgs doublets models (2HDM) with a discrete $Z_2$ symmetry, which couples the heavy scalar doublet only to the 4th generation fermions and the light one to the Standard Model (SM) fermions - the so-called 4G2HDM introduced by us several years ago. We study the constraints imposed on the 4G2HDM from direct searches of heavy fermions, from precision electroweak data (PEWD) and from the measured production and decay signals of the 125 GeV scalar, which in the 4G2HDM corresponds to the lightest CP-even scalar h. We then show that the recently reported excess in the $gammagamma$ spectrum around 750 GeV can be accommodated by the heavy CP-even scalar of the 4G2HDM, H, resulting in a unique choice of parameter space: negligible mixing (sinalpha ~ O(0.001)) between the two CP-even scalars h,H and heavy 4th generation quark and lepton masses m_t,m_b < 400 GeV and $m_{ u},m_{tau}$ > 900 GeV, respectively. Whether or not the 750 GeV gamma gamma resonance is confirmed, interesting phenomenology emerges in q - Higgs systems (q=t,b), that can be searched for at the LHC. For example, the heavy scalar states of the model, S=H,A,H^+, may have BR(S -> qq) ~ O(1), giving rise to observable qq signals on resonance, followed by the flavor changing q decays t->uh (u=u,c) and/or b->dh (d=d,s,b). This leads to distinct high jet-multiplicity signatures, with or without charged leptons, of the form qq -> (nj + mb + lW)_S (j and b being light and b-quark jets, respectively), with n+m+l =6-8 and unique kinematic features. It is also shown that the 4G2HDM can easily accommodate the interesting recent indications of a percent-level branching ratio in the lepton-flavor-violating (LFV) decay $h to tau mu$ of the 125 GeV Higgs, if confirmed.
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.
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 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.
We examine the scenario of a warped extra dimension containing bulk SM fields in light of the observed diphoton excess at 750 GeV. We demonstrate that a spin-2 graviton whose action contains localized kinetic brane terms for both gravity and gauge fields is compatible with the excess, while being consistent with all other constraints. The graviton sector of this model contains a single free parameter, once the mass of the graviton is fixed. The scale of physics on the IR-brane is found to lie in the range of a $sim$ few TeV, relevant to the gauge hierarchy. There remains significant flexibility in the coupled gauge/fermion KK sectors to address the strong constraints arising from precision measurements.
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