Constraining the Higgs boson width with ZZ production at the LHC

We point out that existing measurements of $pp \to ZZ$ cross-section at the LHC in a broad range of ZZ invariant masses allow one to derive a model-independent upper bound on the Higgs boson width, thanks to strongly enhanced off-shell Higgs contribution. Using CMS data and considering events in the interval of ZZ invariant masses from 100 to 800 GeV, we find $Γ_H \le 38.8 \times Γ_H^{SM} \approx 163$ MeV, at the $95\%$ confidence level. Restricting ZZ invariant masses to $M_{ZZ} \ge 300$ GeV range, we estimate that this bound can be improved to $Γ_H \le 21 \times Γ_H^{SM} \approx 88$ MeV. Under the assumption that all couplings of the Higgs boson to Standard Model particles scale in a universal way, our result can be translated into an upper limit on the branching fraction of the Higgs boson decay to invisible final states. We obtain $Br(H \to inv) < 0.84 (0.78)$, depending on the range of ZZ invariant masses that are used to constrain the width. We believe that an analysis along these lines should be performed by experimental collaborations in the near future and also in the run II of the LHC. We estimate that such analyses can, eventually, be sensitive to the Higgs boson width as small as $Γ_H \sim 10 \times Γ_H^{SM}$.

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