A search for decays of the Higgs boson to invisible particles in events with a top-antitop quark pair or a vector boson in proton-proton collisions at s=13TeV

Abstract

A search for decays to invisible particles of Higgs bosons produced in association with a top-antitop quark pair or a vector boson, which both decay to a fully hadronic final state, has been performed using proton-proton collision data collected at $\sqrt{s}=13\text{Te}\text{V}$ by the CMS experiment at the LHC, corresponding to an integrated luminosity of 138${\text{fb}}^{-1}$. The 95% confidence level upper limit set on the branching fraction of the 125$\text{Ge}\text{V}$ Higgs boson to invisible particles, $B(\text{H}\to \text{inv})$, is 0.54 (0.39 expected), assuming standard model production cross sections. The results of this analysis are combined with previous $B(\text{H}\to \text{inv})$ searches carried out at $\sqrt{s}=7$, 8, and 13$\text{Te}\text{V}$ in complementary production modes. The combined upper limit at 95% confidence level on $B(\text{H}\to \text{inv})$ is 0.15 (0.08 expected).

Fig. 1

Representative LO Feynman diagrams for the SM Higgs boson production channels $\text{t}\overline{\text{t}}\text{H}$ and VH

Fig. 2

Distributions of hadronic recoil in the $\text{t}\overline{\text{t}}\text{H}$ (upper plot) and VH (lower plot) categories for the $\mathrm{\mu }+\text{jets}$ CR. The black histogram shows the total background (bkg.) prediction from a CR only, B-only fit, while the red histogram shows the yields from a CR + SR S + B fit. The uncertainty in the predicted background (Bkg. unc.) accounts for both systematic and simulated statistical contributions

Fig. 3

Distributions of hadronic recoil in the $\text{t}\overline{\text{t}}\text{H}$ (upper plot) and VH (lower plot) categories for the $\text{e}+\text{jets}$ CR. The black histogram shows the total background (bkg.) prediction from a CR only, B-only fit, while the red histogram shows the yields from a CR + SR S + B fit. The uncertainty in the predicted background (Bkg. unc.) accounts for both systematic and simulated statistical contributions

Fig. 4

Distributions of hadronic recoil in the $\text{t}\overline{\text{t}}\text{H}$ category for the $\mathrm{\mu }\mathrm{\mu }+$ jets, ee $+$ jets, and $\ell \ell +\text{jets}$ CRs (upper plot), and the VH category for the $\mathrm{\mu }\mathrm{\mu }+$ jets, ee $+$ jets, and $\mathrm{\gamma }+\text{jets}$ CRs (lower plot). The black histogram shows the total background (bkg.) prediction from a CR only, B-only fit, while the red histogram shows the yields from a CR + SR S + B fit. The uncertainty in the predicted background (Bkg. unc.) accounts for both systematic and simulated statistical contributions

Fig. 5

Distributions of hadronic recoil in the $\text{t}\overline{\text{t}}\text{H}$ (upper plot) and VH (lower plot) categories for the SR, showing the signal contributions from $\text{t}\overline{\text{t}}\text{H}$, VH, ggH, and VBF weighted by $\mathcal{B}(\text{H}\to \text{inv})=0.07$. The black histogram shows the total background (bkg.) prediction from a CR only, B-only fit, while the red histogram shows the yields from a CR + SR S + B fit. The uncertainty in the predicted background (Bkg. unc.) accounts for both systematic and simulated statistical contributions

Fig. 6

Left: observed and expected limits at 95% $\text{CL}$ for the $\text{t}\overline{\text{t}}\text{H}$ and VH categories using 2016–2018 data. Right: the profile likelihood scan corresponding to observed and expected (where $\mathcal{B}(\text{H}\to \text{inv})=0$) limits in the fit to the $\text{t}\overline{\text{t}}\text{H}$ and VH categories

Fig. 7

Top: exclusion limits at 95% $\text{CL}$ on $\mathcal{B}(\text{H}\to \text{inv})$. The results are shown separately for each Higgs boson production mode as tagged by the input analyses for Run 1 and Run 2, as well as combined across modes. Bottom: scan of the profile negative log-likelihood as a function of $\mathcal{B}(\text{H}\to \text{inv})$ broken down by the Higgs boson production mode as tagged by the input analyses for Run 1 and Run 2

Fig. 8

Upper limits on ${\sigma }_{\text{DM-nucleon}}^{\text{SI}}$ as a function of DM candidate mass $m_{\text{DM}}$. Results are presented for a fermion (red) and scalar (yellow) DM candidate. In addition, a vector DM candidate is studied using two UV-complete approaches, the first denoted Vector DM$_{}^{\text{UV-complete}}$ [20] (burgundy), and the second a radiative portal version denoted Vector DM$_{m_2}^{\text{radiative}}$ [23] (orange) with a dark Higgs boson mass of $m_2=65$ and $100\text{Ge}\text{V}$. Uncertainties are derived from Refs. [19, 100, 101]. Results are compared to direct-detection searches from XENON1T-Migdal [96], DarkSide-50 [97], PandaX-4T [98], and LUX-ZEPLIN [99]

Fig. 9

Observed 95% $\text{CL}$ upper limit on $\mathcal{B}(\text{H}\to \text{inv})$ as a function of coupling strength modifiers, ${\kappa }_{\text{V}}$ and ${\kappa }_{\text{F}}$, for a Higgs boson of mass 125$\text{Ge}\text{V}$. Best estimates for ${\kappa }_{\text{V}}$ and ${\kappa }_{\text{F}}$ from Ref. [11] are shown as a black cross, together with 68 and 95% $\text{CL}$ contours