Search for exotic decay of the Higgs boson into two light pseudoscalars with four photons in the final state at $\sqrt{s}$ = 13 TeV

A search for exotic decays of the Higgs boson to a pair of light pseudoscalars, each of which subsequently decay to a pair of photons, is presented. The search uses data from proton-proton collisions at $\sqrt{s}$ = 13 TeV recorded with the CMS detector at the LHC, corresponding to an integrated luminosity of ${132\,\mathrm{fb}^{-1}}$. The analysis considers inclusive production mode of the Higgs boson, and probes pseudoscalars ($\mathit{a}$) that range in mass from $15 < m_{a} < 60$ GeV, and leads to four well isolated photons in the final state. No significant deviation from the background-only hypothesis is observed, and upper limits are set on the product of the Higgs boson production cross section and branching fraction into four photons. The observed (expected) limits range from $0.80$ ($1.00$)$\ \mathrm{fb}$ for $m_{a}$ = 15 GeV to $0.33$ ($0.30$)$\ \mathrm{fb}$ for $m_{a}$ = 60 GeV at the 95$\%$ confidence level.