Physics potential for the H$$\rightarrow \hbox {ZZ}^{*}$$ decay at the CEPC

The precision of the yield measurement of the Higgs boson decaying into a pair of Z bosons process at the Circular Electron Positron Collider is evaluated. Including the recoil Z boson associated with the Higgs production (Higgsstrahlung) a total of three Z bosons are involved for this channel, from which final states characterized by the presence of a pair of leptons, quarks, and neutrinos are chosen for the signal. Two analysis approaches are compared and the final statistical precision of $${\sigma }_{\mathrm {ZH}}{\cdot }$$ σ ZH · BR($$H \rightarrow ZZ^{*}$$ H → Z Z ∗ ) is estimated to be 6.9% using a multivariate analysis technique, based on boosted decision trees. The relative precision of the Higgs boson width, using this $$H \rightarrow ZZ^{*}$$ H → Z Z ∗ decay topology, is estimated by combining the obtained result with the precision of the inclusive ZH cross section measurement.

Search for dark matter in events with missing transverse momentum and a Higgs boson decaying into two photons in pp collisions at $$ \sqrt{s} $$ = 13 TeV with the ATLAS detector

A search for dark-matter particles in events with large missing transverse momentum and a Higgs boson candidate decaying into two photons is reported. The search uses 139 fb−1 of proton-proton collision data collected at $$ \sqrt{s} $$ s = 13 TeV with the ATLAS detector at the CERN LHC between 2015 and 2018. No significant excess of events over the Standard Model predictions is observed. The results are interpreted by extracting limits on three simplified models that include either vector or pseudoscalar mediators and predict a final state with a pair of dark-matter candidates and a Higgs boson decaying into two photons.

Search for a heavy Higgs boson decaying into a Z boson and another heavy Higgs boson in the $$\ell \ell bb$$ and $$\ell \ell WW$$ final states in pp collisions at $$\sqrt{s}=13$$ $$\text {TeV}$$ with the ATLAS detector

A search for a heavy neutral Higgs boson, A, decaying into a Z boson and another heavy Higgs boson, H, is performed using a data sample corresponding to an integrated luminosity of 139 fb$$^{-1}$$ - 1 from proton–proton collisions at $$\sqrt{s} = 13$$ s = 13 $$\text {TeV}$$ TeV recorded by the ATLAS detector at the LHC. The search considers the Z boson decaying into electrons or muons and the H boson into a pair of b-quarks or W bosons. The mass range considered is 230–800 $$\text {GeV}$$ GeV for the A boson and 130–700 $$\text {GeV}$$ GeV for the H boson. The data are in good agreement with the background predicted by the Standard Model, and therefore 95% confidence-level upper limits for $$\sigma \times B(A\rightarrow ZH)\times B(H\rightarrow bb \; \text {or} \; H \rightarrow WW)$$ σ × B ( A → Z H ) × B ( H → b b or H → W W ) are set. The upper limits are in the range 0.0062–0.380 pb for the $$H\rightarrow bb$$ H → b b channel and in the range 0.023–8.9 pb for the $$H\rightarrow WW$$ H → W W channel. An interpretation of the results in the context of two-Higgs-doublet models is also given.

Measurements of WH and ZH production in the $$H \rightarrow b\bar{b}$$ decay channel in pp collisions at $$13\,\text {Te}\text {V}$$ with the ATLAS detector

Measurements of the Standard Model Higgs boson decaying into a $$b\bar{b}$$ b b ¯ pair and produced in association with a W or Z boson decaying into leptons, using proton–proton collision data collected between 2015 and 2018 by the ATLAS detector, are presented. The measurements use collisions produced by the Large Hadron Collider at a centre-of-mass energy of $$\sqrt{s} = 13\,\text {Te}\text {V}$$ s = 13 Te , corresponding to an integrated luminosity of $$139\,\mathrm {fb}^{-1}$$ 139 fb - 1 . The production of a Higgs boson in association with a W or Z boson is established with observed (expected) significances of 4.0 (4.1) and 5.3 (5.1) standard deviations, respectively. Cross-sections of associated production of a Higgs boson decaying into bottom quark pairs with an electroweak gauge boson, W or Z, decaying into leptons are measured as a function of the gauge boson transverse momentum in kinematic fiducial volumes. The cross-section measurements are all consistent with the Standard Model expectations, and the total uncertainties vary from 30% in the high gauge boson transverse momentum regions to 85% in the low regions. Limits are subsequently set on the parameters of an effective Lagrangian sensitive to modifications of the WH and ZH processes as well as the Higgs boson decay into $$b\bar{b}$$ b b ¯ .