HEPData Search

Cut-flow and number of events in a region with $110 \text{ GeV} <m_{aa}<130 \text{ GeV}$ for selected signal samples

Overview of relative systematic uncertainties on the signal normalization for selected couplings and mass points in the dominant categories. All photon related uncertainties are summarized under "standard photon", while all customised photon related uncertainties (e.g. displaced photons, NN-based photon IDs) are summarized under "custom photon".

Exclusion limits for $C_{a\gamma\gamma}=1$

Upper limits on $\mathcal{B}(H\rightarrow aa\rightarrow 4\gamma)$ at 95% CL as a function of the axion mass and for ALP-photon coupling $C_{a\gamma\gamma}=1$.

Exclusion limits for $C_{a\gamma\gamma}=0.01$

Upper limits on $\mathcal{B}(H\rightarrow aa\rightarrow 4\gamma)$ at 95% CL as a function of the axion mass and for ALP-photon coupling $C_{a\gamma\gamma}=0.01$.

Exclusion limits for $C_{a\gamma\gamma}=5\times10^{-4}$

Upper limits on $\mathcal{B}(H\rightarrow aa\rightarrow 4\gamma)$ at 95% CL as a function of the axion mass and for ALP-photon coupling $C_{a\gamma\gamma}=5\times10^{-4}$

Exclusion limits for $C_{a\gamma\gamma}=10^{-5}$

Upper limits on $\mathcal{B}(H\rightarrow aa\rightarrow 4\gamma)$ at 95% CL as a function of the axion mass and for ALP-photon coupling $C_{a\gamma\gamma}=10^{-5}$

Exclusion limits for prompt analysis

Upper limits on $B(H\rightarrow 4\gamma)$ at 95% CL as a function of the signal mass hypothesis and for the assumption of promptly decaying ALPs.

Tight efficiency

Identification efficiency for isolated photons that pass the tight photon ID requirements in dependence of the opening angle in $\Delta R$ of both decay photons of the axion and the decay radius of the originating axion from the primary vertex for axions with masses between 100 MeV and 300 MeV. All four axion decay photons on MC truth level are required to fulfil $|\eta|<2.5$ and $p_T>5$ GeV. Only a mild dependency on the decay radius can be seen, since the distance between the two photons is small and hence the combined decay signature in the calorimeter still points to the primary vertex.

Merged efficiency

Efficiency for classified merged isolated photons in dependence of the opening angle in $\Delta R$ of both decay photons of the axion and the decay radius of the originating axion from the primary vertex for axions with masses between 100 MeV and 300 MeV. All four axion decay photons on MC truth level are required to fulfil $|\eta|<2.5$ and $p_T>5$ GeV. Only a mild dependency on the decay radius can be seen, since the distance between the two photons is small and hence the combined decay signature in the calorimeter still points to the primary vertex.

2D exclusion limits

Limits on the ALP mass and coupling to photons at 95\%~CL, assuming $\mathcal{B}(a\rightarrow\gamma\gamma) = 1$, $\Lambda = 1\,TeV$ with $|C_{aH}^{\text{eff}}|$ = $1$ (solid line) and $|C_{aH}^{\text{eff}}|$ = $0.1$.

Data background comparison

The number of data and estimated background events in the signal region of the most sensitive categories..

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HistFactory
Search for short- and long-lived axion-like particles in $H\rightarrow a a \rightarrow 4\gamma$ decays with the ATLAS experiment at the LHC