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CMS's biggest Higgs combination matches the Standard Model at 5 percent precision
CMS combined 138 fb-1 of 2016-2018 collision data and measured a Higgs signal strength of 1.01 +/- 0.05, against a Standard Model value of 1. Any new physics that alters the Higgs rate now has room mainly near or below that 5 percent precision.
The Scientist · Science desk
What happened
- Physics World reports that the combination finds no significant deviations from theory at current experimental precision.
- The analysis pooled many Higgs decay channels, including decays into photons, bosons and leptons.
- It also searched for invisible Higgs decays, in which the Higgs would produce undetectable particles such as dark matter candidates.
- CMS studied rare off-shell production too, where the Higgs appears as a virtual state with a mass different from its physical mass.
- The CMS Collaboration published the results in 2026 as Rep. Prog. Phys. 89 087801.
Compiled by The ScientistSomething wrong?How this is made
Why it matters
- constraint Standard Model extensions that predict large changes in Higgs production or decay lose room; the ones still viable must keep their effects inside a band a few percent wide.
- decision Detecting a deviation below the current 5 percent precision takes many more rare Higgs events, so the next real test of these theories depends on datasets larger than 138 fb-1.
- precedent Future search programmes at the LHC and other experiments will be planned around the narrower deviation range this combination leaves open.
The measured 1.01 sits 0.01 above the Standard Model value [3]. That offset is one fifth of the quoted uncertainty [1]. The particle was predicted in the 1960s and found in 2012 [12]. "It is amazing to see how far we have come in just over a decade since discovery," said Jonathon Langford of Imperial College London, a lead analyst for the paper [13]. "We are now able to measure the Higgs boson production rate at the LHC with a 5% precision, confirming our theories regarding the origin of mass in the Universe," he said [13].
The result shows agreement at about the 5 percent level. Physics World's account is careful here, saying the Higgs behaves as predicted "with the current experimental precision" [8]. One uncertainty either side of the measurement spans 0.96 to 1.06 [2]. A new-physics effect that moved the overall rate by 2 or 3 percent would fit inside that band [2]. An effect large enough to push the rate to 0.90 or 1.10 would sit about two uncertainties from the measured value [3].
Many extensions of the Standard Model predict that undiscovered particles or forces would subtly alter how the Higgs is produced or how it decays [9]. According to Physics World, the CMS agreement leaves little evidence for such effects and significantly constrains many of those theories [9]. I'd expect the pressure to fall hardest on models whose predicted shifts are large compared with 0.05. Those are the ones this measurement can tell apart from the Standard Model [3].
The design explains the precision. This is the largest combined CMS study of Higgs production and decay [2]. Collisions that make a Higgs are rare, so the analysis needed a very large sample [4], and it pooled many decay channels [5]. Pooling adds statistical power. It also makes the combined value an average, and an average can sit near 1 while individual channels pull in opposite directions. The Physics World summary reports only the combined figure. The channel-by-channel results, and the numbers from the invisible-decay and off-shell studies, are in the full paper the CMS Collaboration published in Reports on Progress in Physics [10].
What to watch
- Per-channel signal strengths in Rep. Prog. Phys. 89 087801, and whether any single channel sits well away from 1 while the combined value holds at 1.01.
- Analyses using more than 138 fb-1 that shrink the 0.05 uncertainty enough to test deviations of a percent or two.
- The invisible-decay bound in the full paper, as a limit on how often the Higgs could decay to dark matter candidates.