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Abstract
The recently observed excess in diphoton events at around 750\,GeV can be satisfactorily described in terms of a new spin-0 real singlet with effective interactions to the gauge bosons. In this letter we first review the current constraints on this setup. We further explore the production in association with a gauge boson. We show the potential of this channel to unravel current flat directions in the allowed parameter space. We then study the potential of two different asymmetries for disentangling the CP nature of such a singlet in both gluon fusion and vector-boson fusion. For this matter, we perform an estimation of the efficiency for selecting signal and background events in eight different decay modes, namely $4\ell, 2j\, 2\ell, 2j\ell\,E_T^\text{miss}, 2\gamma\,2j, 4\ell\,2j, 2\ell\,\gamma\,2j, 4j\,2\ell$ and $4j\,\ell\,E_T^\text{miss}$. We emphasize that the very different couplings of this new singlet to the Standard Model particles as well as the larger mass provide a distinctive phenomenology with respect to Higgs searches. We finally show that a large region of the parameter space region could be tested within the current LHC run, the dominant channel being $2\gamma\, 2j$.
Highlights
√ The first bunch of data in proton–proton collisions at s = 13 TeV were successfully delivered by the LHC during last year
For each point in the parameter space region and for each of the eight event categories i defined for gluon fusion (GF) and vector-boson fusion (VBF), we compute AGF and AVBF by estimating the number of signal and background events
We have checked that this is the case in almost the whole parameter space, small variations arising only in the VBF 2γ 2 j channel for cWW cγ γ
Summary
The reported excess survived further scrutiny [3] and appears as the best hint in decades for physics beyond the Standard Model (SM) at colliders This fact explains the excitement of the particle physics community, which has translated into a plethora of papers in a few months [4]. This diphoton excess can be interpreted in terms of a spin-0 real singlet ( explanations in terms of spin-1 and spin-2 particles have received some well deserved attention). Production via gluon fusion (GF) and vector-boson fusion (VBF) turn out to be sizable in a large region of the parameter space They are shown to give flat directions that can be only disentangled if new production mechanisms are considered.
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