Abstract (data abstract)

Search for a new heavy scalar particle decaying into a Higgs boson and a new scalar singlet in final states with one or two light leptons and a pair of $\tau$-leptons with the ATLAS detector. A search for a new heavy scalar particle $X$ decaying into a Standard Model (SM) Higgs boson and a new singlet scalar particle $S$ is presented. The search uses a proton-proton ($pp$) collision dataset with an integrated luminosity of 140 fb$^{-1}$ recorded at a center-of-mass energy of $\sqrt{s} = 13$ TeV with the ATLAS detector at the Large Hadron Collider. The explored $X$ masses range from 500 to 1500 \GeV\,with the corresponding $S$ mass varying from 200 to 500 GeV. The search selects events with two hadronically decaying $\tau$-lepton candidates from $H\to \tau^+\tau^-$ decays and one or two light leptons ($\ell=e,\,\mu$) from $S\to VV$ ($V = W,\,Z$) decays. A multivariate discriminant based on event kinematics is used to separate signal from background. No excess events were observed beyond the expected SM background and 95\% confidence level upper limits between 72 fb and 542 fb are derived on the cross-section for $\sigma(pp\to X\to SH)$ assuming the SM-Higgs boson-like $S\to VV$ decay. Upper limits on the visible cross-section for $\sigma(pp\to X\to SH \to WW\tau\tau)$ and $\sigma(pp\to X\to SH \to ZZ\tau\tau)$ are also set in the ranges 3--26 fb and 6--33 fb, respectively.

Table 1

Data from Figure 4 (a)

10.17182/hepdata.141076.v1/t1

Observed and expected 95% CL upper limits are shown for $\sigma(pp\to X\to SH)$ obtained from $WW1\ell2\tau_{\mathrm{had}}$, $WW2\ell2\tau_{\mathrm{had}}$, $ZZ2\ell2\tau_{\mathrm{had}}$, and their...
Table 2

Data from Figure 4 (b)

10.17182/hepdata.141076.v1/t2

Observed and expected 95% CL upper limits are shown for $\sigma(pp\to X\to SH\to WW\tau\tau)$ obtained from the combination of $WW1\ell2\tau_{\mathrm{had}}$...
Table 3

Data from Figure 4 (c)

10.17182/hepdata.141076.v1/t3

Observed and expected 95% CL upper limits are shown for $\sigma(pp\to X\to SH\to ZZ\tau\tau)$ obtained from $ZZ2\ell2\tau_{\mathrm{had}}$ channel, as a...
Table 4

Data from Table 3

10.17182/hepdata.141076.v1/t4

Event yields after a background-only fit and data in the three signal regions. All the backgrounds except the fake $\tau_{\mathrm{had}}$...
Table 5

Data from Table 4

10.17182/hepdata.141076.v1/t5

Uncertainties on $\sigma(pp\to X\to SH)$ obtained from the combined fit to the data for the least and most sensitive mass...
Table 6

Data from Table 5

10.17182/hepdata.141076.v1/t6

Summary of observed and expected 95\% CL upper limits on the production cross-section of $\sigma(pp\to X\to SH)$ in fb in...

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