CERN Accelerating science

ATLAS Slides
Report number	ATL-PHYS-SLIDE-2025-622
Title	Search for Higgs boson decays into a pair of pseudoscalar particles in the $\gamma\gamma\tau\tau$ final state using $pp$ collisions at $\sqrt{s} = 13$ TeV with the ATLAS detector
Author(s)	Aikot, Arya (Univ. of Valencia and CSIC (ES))
Corporate author(s)	The ATLAS collaboration
Collaboration	ATLAS Collaboration
Submitted to	The 32nd International Symposium on Lepton Photon Interactions at High Energies (Lepton Photon 2025), Madison, Wisconsin, Us, 25 - 29 Aug 2025
Submitted by	arya.aikot@cern.ch on 10 Nov 2025
Subject category	Particle Physics - Experiment
Accelerator/Facility, Experiment	CERN LHC ; ATLAS
Free keywords	EXOTICS
Abstract	Many well-motivated extensions of the Standard Model predict light (pseudo)scalars, referred to as 𝑎 bosons, that couple to the 125 GeV Higgs boson, enabling new exotic decay modes. This study presents a search for Higgs boson decays into a pair of such particles, $H\rightarrow bb$, where one 𝑎-boson decays into a photon pair and the other into a $\tau$-lepton pair, performed for the first time at the Large Hadron Collider. Both $\tau$-leptons are reconstructed in their hadronic decay modes using a novel dedicated tagger for collimated $\tau$-lepton pairs. The search uses 140/fb of proton–proton collision data at a centre-of-mass energy of $\sqrt{s} = 13$ TeV recorded between 2015 and 2018 by the ATLAS experiment. The search is performed in the mass range of the $a$ boson between 10 GeV and 60 GeV.