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Title: Is the Higgs total decay width equal to the SM 4.1 MeV?
Plain: The width of the Higgs measures how fast it decays and counts every decay, including decays to unknown particles. The SM predicts 4.1 MeV, far too narrow to resolve directly at the LHC.
Precise: Determine $\Gamma_H$ with $\le 5\ \mathrm{percent}$ uncertainty (SM: $4.1\ \mathrm{MeV}$). CMS used off-shell $H* \to \mathrm{ZZ}$ production to obtain $\Gamma_H=3.2+2.4-1.7\ \mathrm{MeV}$ (Nature Physics 18, 1329, 2022), a method that assumes equal coupling modifiers on and off shell. An answer is a model-independent $\Gamma_H$, which bounds the total rate of undetected and invisible decays.
Settled by: A Higgs-factory measurement of $\sigma(e+ e- \to \mathrm{ZH})$ by the recoil-mass method combined with $\mathrm{BR}(H \to \mathrm{ZZ}*)$ or $\mathrm{BR}(H \to \mathrm{WW}*)$, giving $\Gamma_H$ without model assumptions at the percent level.
Kind: well-posed
Answer type: value
References: (empty)
Literature status: open
Status note: The 2022 CMS off-shell result agrees with the SM within errors of about 60 percent.
Posed since: (empty)