Search for exotic Higgs boson decays H $\to$ $\mathcal{AA}$ with $\mathcal{AA}$ $\to$ $\gamma\gamma$ in events with a semi-merged topology in proton-proton collisions at $\sqrt{s}$ = 13 TeV

TL;DR

This paper reports a search for exotic Higgs decays into pairs of light particles that decay into photons, using CMS data at 13 TeV, setting the most stringent limits to date for certain mass ranges.

Contribution

First search for H → AA with A → γγ in semi-merged topology, providing new upper limits on the decay rate for light A particles in proton-proton collisions.

Findings

No significant excess over background observed.

Set upper limits on σ(pp → H)×B(H → AA → 4γ) from 0.264 to 0.005 pb.

Most stringent limits for A mass between 1 and 5 GeV.

Abstract

A search for exotic Higgs boson decays H $\to$ $\mathcal{AA}$, with $\mathcal{A}$ $\to$ $\gamma\gamma$ is presented, using events with a semi-merged topology. One of the hypothetical particles, $\mathcal{A}$, is assumed to decay promptly into a semi-merged diphoton system reconstructed as a single photon-like object, while the other $\mathcal{A}$ decays into two resolved photons. The search is performed using proton-proton collision data collected by the CMS experiment at $\sqrt{s}$ = 13 TeV, corresponding to an integrated luminosity of 138 fb$^{-1}$. The data agree with the standard model background expectation. Upper limits are set on the product of the Higgs boson production cross section and the branching fraction, $\sigma$(pp $\to$ H)$\mathcal{B}$(H $\to$ $\mathcal{AA}$ $\to$ 4$\gamma$), which range from 0.264 to 0.005 pb at 95% confidence level, for $\mathcal{A}$ masses in the range 1 $\lt$ $m_\mathcal{A}$ $\lt$ 15 GeV. These limits are the most stringent to date in the 1$-$5 GeV $m_\mathcal{A}$ range.