Abstract:
Presented is the search for anomalous Higgs boson decays into two axion-like particles (ALPs) using the full Run 2 data set of $$140\,\text {fb}^{-1}$$
140
fb
-
1
of proton-proton collisions at a centre-of-mass energy of $$13\,\text {TeV}$$
13
TeV
recorded by the ATLAS experiment. The ALPs are assumed to decay into two photons, providing sensitivity to recently proposed models that could explain the $$(g-2)_\mu $$
(
g
-
2
)
μ
discrepancy. This analysis covers an ALP mass range from 100 to $$62\,\text {GeV}$$
62
GeV
and ALP-photon couplings in the range $$10^{-7}\,\text {TeV}^{-1}
10
-
7
TeV
-
1
<
C
a
γ
γ
/
Λ
<
1
TeV
-
1
, and therefore includes signatures with significantly displaced vertices and highly collinear photons. No significant excess of events above the Standard Model background is observed. Upper limits at 95% confidence level are placed on the branching ratio of the Higgs boson to two ALPs in the four-photon final state, and are in the range of $$ 10^{-5}$$
10
-
5
to $$3\times 10^{-2}$$
3
×
10
-
2
, depending on the hypothesized ALP mass and ALP-photon coupling strength.
