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Register a new userOn the possible new 750 GeV heavy boson resonance at the LHC
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Authors
Davor Palle
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We argue that the possible new heavy boson resonance of 750 GeV is an ideal candidate as a twin particle of the 125 GeV scalar boson, both emerging from the large mixing of the scalar toponium and scalar gluonium. Assuming that the mixing of the pseudoscalar toponium and pseudoscalar gluonium is small, just like the mixing of the light pseudoscalar quarkonium and pseudoscalar gluonium, the resulting new physical pseudoscalars are lighter than the scalar twins. The discovery of the 750 GeV resonance is possible only with a much more data than for the 125 GeV resonance since only the gluonium component is detectable above the toponium threshold. The CMS announced recently a possible new boson resonance with the mass of roughly 30 GeV in the di-muon channel search. The resonance in the di-muon channel with a similar mass and width was also reported by A. Heister in 2016 in the analysis of the old LEP ALEPH data. If real, this resonance can be interpreted within the plain QCD as a lighter twin of the pseudoscalar toponium and gluonium mixture. The absence of the Higgs scalar should not be considered an obstacle because the nonsingular theory with the UV cutoff fixed by the weak boson masses is superior to the Standard Model since it solves a few SM fundamental problems such as: (1) light neutrinos, (2) dark matter particles to be the heavy Majorana neutrinos and (3) broken lepton and baryon numbers.
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We propose that the 750 GeV resonance, presumably observed in the early LHC Run 2 data, could be a heavy composite axion that results from condensation of a hypothetical quark in a high-colour representation of conventional QCD. The model, motivated by a recently proposed solution to the strong CP problem, is very economical and is essentially defined by the properties of the additional quark - its colour charge, hypercharge and mass. The axion mass and its coupling to two photons (via axial anomaly) can be computed in terms of these parameters. The axion is predominantly produced via photon fusion ($gammagamma to {cal A}$) which is followed by $ Z $ vector boson fusion and associated production at the LHC. We find that the total diphoton cross section of the axion can be fitted with the observed excess. Combining the requirement on the cross-section, such that it reproduces the diphoton excess events, with the bounds on the total width ($Gamma_{tot} leqslant 45$ GeV), we obtain the effective coupling in the range $1.6times 10^{-4}$ GeV$^{-1}gtrsim C_{{cal A}} gtrsim 6.5times 10^{-5}$ GeV$^{-1}$. Within this window of allowed couplings the model favours a narrow width resonance and $ y_{Q}^2 sim mathcal{O}(10)$. In addition, we observe that the associated production $qbar{q} to {cal A}gammato gammagammagamma$ can potentially produce a sizeable number of three photon events at future LHC and $ e^{+} e^{-} $ colliders. However, the rare decay $Ztomathcal{A}^*gamma to gammagammagamma$ is found to be too small to be probed at the LHC.
Motivated by the recent diphoton excesses reported by both ATLAS and CMS collaborations, we suggest that a new heavy spinless particle is produced in gluon fusion at the LHC and decays to a couple of lighter pseudoscalars which then decay to photons. The new resonances could arise from a new strongly interacting sector and couple to Standard Model gauge bosons only via the corresponding Wess-Zumino-Witten anomaly. We present a detailed recast of the newest 13 TeV data from ATLAS and CMS together with the 8 TeV data to scan the consistency of the parameter space for those resonances.
Non-observation of superpartners of the Standard Model particles at the early runs of the LHC provide strong motivation for an $R$-symmetric minimal supersymmetric Standard Model, or MRSSM. This model also comes with a pair of extra scalars which couple only to superpartners at the tree level. We demonstrate that in the limit when the $U(1)_R$ symmetry is broken, one of these scalars develops all the properties necessary to explain the 750 GeV diphoton resonance recently observed at the LHC, as well as the non-observation of associated signals in other channels. Some confirmatory tests in the upcoming LHC runs are proposed.
Motivated by the recent LHC discovery of the di-photon excess at the invariant mass of ~ 750 GeV, we study the prospect of investigating the scalar resonance at a future photon-photon collider. We show that, if the di-photon excess observed at the LHC is due to a new scalar boson coupled to the standard-model gauge bosons, such a scalar boson can be observed and studied at the photon-photon collider with the center-of-mass energy of ~ 1 TeV in large fraction of parameter space.
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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