Search for New Resonances Decaying to Pairs of Merged Diphotons in Proton-Proton Collisions at $ \sqrt{s}=13\text{}\text{}\mathrm{TeV}$

A search is presented for an extended Higgs sector with two new particles, $ X$ and $ \varphi $, in the process $ X\to \varphi \varphi \to (\gamma \gamma )(\gamma \gamma )$. Novel neural networks classify events with diphotons that are merged and determine the diphoton masses. The search uses LHC proton-proton collision data at $ \sqrt{s}=13\text{}\text{}\mathrm{TeV}$ collected with the CMS detector, corresponding to an integrated luminosity of $ 138\text{}\text{}{\mathrm{fb}}^{-1}$. No evidence of such resonances is seen. Upper limits are set on the production cross section for $ {m}_{X}$ between 300 and 3000 GeV and $ {m}_{\varphi }/{m}_{X}$ between 0.5% and 2.5%, representing the most sensitive search in this channel.