Isolating top contributions in the production of the 750 GeV diphoton excess

Zhang, Hao

doi:10.1103/physrevd.93.114032

Phys. Rev. D

2016

DOI: 10.1103/physrevd.93.114032

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Isolating top contributions in the production of the 750 GeV diphoton excess

Hao Zhang

Abstract: Recently, both ATLAS and CMS collaborations report an excess at 750GeV in the diphoton invariant mass spectrum at 13TeV LHC. If it is a new (pseudo)scalar produced via loop induced gluon-gluon fusion process, it is important to know what is the particle in the loop. In this work, we investigate the possibility of determine the fraction of the contribution from the standard model top-quark in the loop.

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Cited by 5 publications

References 111 publications

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Diphoton decay for a 750 GeV scalar boson in a SU (6)⊗ U (1) X model

et al. 2016

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We propose a new SU (6) ⊗ U (1)X GUT model free from anomalies, with a 750 GeV scalar candidate which can decay into two photons, compatible with the recent diphoton signal reported by ATLAS and CMS collaborations. This model gives masses to all fermions and may explain the 750GeV signal through one loop decays to γγ with charged vector and charged Higgs bosons, as well as up-and electron-like exotic particles that arise naturally from the condition of cancellation of anomalies of the SU (6) ⊗ U (1)X group. We obtain, for different width approximations, allowed mass regions from 900 GeV to 3 TeV for the exotic up-like quark, in agreement with ATLAS and CMS collaborations data.Recently the ATLAS and CMS collaborations reported a diphoton signal excess with invariant mass of 750 GeV [1, 2] which has been the subject of many interpretations in the literature using different extensions of the standard model (SM) [3,4,5,6,7,8,9,10,11]. In this work, we consider the SU (6) ⊗ U (1) X extension proposed in [13] in the framework of the flipped SU (6) models [12] as a feasible model that may explain the diphoton excess. These kind of flipped models have very interesting features. First, by requiring a high breaking scale (∼ 10 17 GeV) for the flipped SU (6) and its SU (5) subgroup [14] the proton decay problem can be avoid. Second, they are able to solve the doublet-triplet splitting problem through the pseudo-Goldstone mechanism as in SU (6) [15,16] and [SU (3)] 3 [17]. Also, they provide unification of gauge couplings as in the flipped SU (5) model [18,19]. Finally, these models may develop see-saw masses compatible with the phenomenological active neutrinos [20,21] if one singlet heavy state is introduced.The SU (6) ⊗ U (1) X extension considered here contains the SU (3) C ⊗ SU (3) L ⊗ U (1) X model (hereafter 331 model) [22,23,24,25] as a subgroup that allow us address the observed diphoton excess through new exotic charged Higgs bosons into the loop at the TeV scale. In the flipped model, the U (1) X symmetry changes the exotic down type quark (charge −1/3) by an up type quark (charge 2/3) in the multiplets, which increases the coupling with photons and gluons into the loop, resulting in a significantly enhanced pp → γγ cross section, compatible with the reported data.The 331 model can be embedded into the grand unified group SU (6) ⊗ U (1) X with the following spontaneous symmetry breaking (SSB) chain:

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Diphoton decay for a 750 GeV scalar boson in a SU (6)⊗ U (1) X model

et al. 2016

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Realizing dark matter and Higgs inflation in light of LHC diphoton excess

Ge¹,

He²,

Ren³

et al. 2016

Physics Letters B

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LHC Run-2 has provided intriguing di-photon signals of a new resonance around 750 GeV, which, if not due to statistical fluctuations, must call for new physics beyond the standard model (SM) at TeV scale. We propose a minimal extension of the SM with a complex singlet scalar S and a doublet of vector-like quarks. The scalar sector respects CP symmetry, with its CP-odd imaginary component χ providing a natural dark matter (DM) candidate. The real component of S serves as the new resonance (750 GeV) and explains the diphoton excess of the LHC Run-2. The new scalar degrees of freedom of S help to stabilize the Higgs vacuum, and can realize the Higgs inflation around GUT scale, consistent with the current cosmological observations. We construct two representative samples A and B of our model for demonstration. We study the mono-jet signals of DM production from invisible decays Re(S) → χχ at the LHC Run-2. We further derive the DM relic density bound, and analyze constraints from the direct and indirect DM detections.The SM Higgs potential suffers vacuum instability at scales above ∼ 10 11 GeV [7,8], and new physics is needed to stabilize the vacuum and realize successful cosmic inflation in the early universe. In particular, the most economical approach of inflation is the Higgs inflation [9][10], where the inflaton is identified as the SM Higgs boson, and including proper new physics is required [11,12]. It was shown before that a minimal extension [12] can save the Higgs inflation by introducing only a real singlet scalar and a vector-like quark at TeV scale. The other serious defect of the SM is its lack of DM candidate to provide the required 28% composition of our universe. For this work, we will present a minimal construction of new physics to resolve three things altogether: (i) consistent realization of Higgs inflation around GUT scale; (ii) natural DM candidate to explain the observed DM relic abundance; (iii) a new scalar state with mass ∼ 750 GeV to induce the enhanced di-photon excess at the LHC Run-2 [1] [2]. For this purpose, our minimal extension includes a complex singlet scalar S and a doublet of vector-like quarks with electric charges 5 3 , 2 3 . The scalar sector respects CP symmetry, with the SM-like light Higgs boson h (125GeV) acting as the inflaton in the early universe. The CP-odd imaginary component Im(S) provides a stable DM candidate, while the real component Re(S) serves as the new resonance (750 GeV), which is produced by gluon fusion via vector-quark triangle loops, with di-photon decays to give the observed LHC excess. The new scalar degrees of freedom of S help to stabilize the Higgs vacuum, and thus realize successful Higgs inflation around GUT scale, consistent with the current cosmology observation.This paper is organized as follows. In section 2, we construct a minimal extension with a complex singlet scalar S and a doublet of vector-like quarks (T , T ) T at TeV scale. Then, in section 3 we study the decays and production of the CP-even component of S , and realize the observed ...

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Diphoton excess and running couplings

et al. 2016

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The recently observed diphoton excess at the LHC may suggest the existence of a singlet (pseudo-) scalar particle with a mass of 750 GeV which couples to gluons and photons. Assuming that the couplings to gluons and photons originate from loops of fermions and/or scalars charged under the Standard Model gauge groups, we show that there is a model-independent upper bound on the cross section σ(pp → S → γγ) as a function of the cutoff scale Λ and masses of the fermions and scalars in the loop. Such a bound comes from the fact that the contribution of each particle to the diphoton event amplitude is proportional to its contribution to the one-loop β functions of the gauge couplings. We also investigate the perturbativity of running Yukawa couplings in models with fermion loops, and show the upper bounds on σ(pp → S → γγ) for explicit models.

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Isolating top contributions in the production of the 750 GeV diphoton excess

Cited by 5 publications

References 111 publications

Diphoton decay for a 750 GeV scalar boson in a SU (6)⊗ U (1) X model

Diphoton decay for a 750 GeV scalar boson in a SU (6)⊗ U (1) X model

Realizing dark matter and Higgs inflation in light of LHC diphoton excess

Diphoton excess and running couplings

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