First interpretation of the 750 GeV diphoton resonance at the LHC

Abstract

We scrutinise the evidences recently reported by the ATLAS and CMS collaborations for compatible 750 GeV resonances which appear in the di-photon channels of the two experiments in both the 8 TeV and 13 TeV datasets. Similar resonances in di-boson, di-lepton, di-jet and tt final states are instead not detected. After discussing the properties and the compatibility of the reported signals, we study the implications on the physics beyond the Standard Model with particular emphasis on possible scalar extensions of the theory such as singlet extensions and the two Higgs doublet models. We also analyse the significance of the new experimental indications within the frameworks of the minimal supersymmetric standard model and of technicolour models. Our results show that a simple effective singlet extension of the SM achieves phenomenological viability with a minimal number of free parameters. The minimal supersymmetric model and the two Higgs doublet model, on the other hand, cannot explain the 750 GeV di-photon excess. Compatibility with the observed signal requires the extension of the particle content of these models, for instance by heavy vector quarks in the case of the two Higgs doublet model.

Two Higgs doublets to explain the excesses pp → γγ(750 GeV) and h → τ ± μ ∓

“…The aim of the present paper is to study whether a simple 2HDM could explain both the diphoton excess and the LFV Higgs decay. The LHC excess has been studied in the 2HDM in [4][5][6][7][8][9][10][11][12], and several authors have combined it with other observables, such as the dark matter abundance [64][65][66][67][68][69][70][71][72][73], or B-physics anomalies [95][96][97]. In the 2HDM, candidates for the 750 GeV resonance are the heavier scalar Higgs h 2 and the pseudoscalar A.…”

Interference effects in the decays of spin-zero resonances into γγ and t t ¯ $$ t\overline{t} $$

“…8 In these cases, the cross sections come from the qq initial state and, because one is dealing with electroweak particles, there is no interference with the colored qq → tt background. Therefore, in the cases of such resonances, one simply expects an excess or a peak on top of the continuum background.…”

“…Nevertheless, searches for resonances decaying into tt final states have been conducted by ATLAS [31] and CMS [32] and interpreted in various scenarios, although mainly for spin-1 and spin-2 resonances where interference effects do not occur. 8 They set strong constraints on the cross sections of the resonances that need to be taken into account.…”

“…If the total Φ decay width is much larger than the minimal width given by anomalous triangle diagrams, the bulk of its decays may be into tt final states, which are dominant in two-Higgs doublet models, see for example [6]. These decays, which have received scant attention (but see also [7][8][9][10][11]), are also potentially observable.…”

750 GeV diphoton excess confronted with a top-pion in the TTM model

“…In this connection various interesting possibilities have been proposed to explain the signal . One solution of particular interest is to consider S as a composite particle due to the confinement of a new strong dynamics [67][68][69][70][71][72][73][74][75][76][77][78][79][80][81]. This idea can be traced back to the technicolor (TC) theory which serves as an alternative for the electroweak symmetry breaking [82].…”