CMS-PAS-EXO-22-022

CMS-PAS-EXO-22-022
Search for new resonances decaying to pairs of highly merged diphotons in proton-proton collisions at 13 TeV
CMS Collaboration
5 December 2023

Abstract: A search for a massive resonance $ \mathrm{X} $ decaying to a pair of spin-0 bosons $ \phi $ that themselves decay to pairs of photons ($ \gamma $), is presented. The search is based on CERN LHC proton-proton collision data at $ \sqrt{s}= $ 13 TeV, collected with the CMS detector, corresponding to an integrated luminosity of 138 fb$ ^{-1} $. The analysis considers masses $ m_{\mathrm{X}} $ between 0.3 and 3 TeV, and is restricted to values of $ m_\phi $ for which the ratio $ m_\phi / m_{\mathrm{X}} $ is between 0.5% and 2.5%. In these ranges the two photons from each $ \phi $ boson are expected to spacially overlap significantly in the detector. Neural networks are created to classify events containing such diphotons and to reconstruct the mass of the diphoton object. The mass spectra are analyzed for the presence of new resonances, and are found to be consistent with standard model expectations. The largest observed excess corresponds to about $ m_{\mathrm{X}}= $ 720 GeV and $ m_\phi= $ 5.04 GeV with a local (global) significance of 3.57 (1.07) standard deviations. Model-specific limits are set at 95% confidence level on the production cross section for $ \mathrm{X}\to \phi\phi \to (\gamma \gamma)(\gamma \gamma) $ as a function of the resonances' masses, where both the $ \mathrm{X}\to \phi\phi $ and $ \phi \to \gamma \gamma $ branching fractions are assumed to be 100%. Observed (expected) limits range from 0.03-1.06 fb (0.03-0.79 fb) for the masses considered, representing the most sensitive search of its kind at the LHC.
Links: CDS record (PDF) ; Physics Briefing ; CADI line (restricted) ; These preliminary results are superseded in this paper, Submitted to PRL. The superseded preliminary plots can be found here.

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