22 September 2026

Photo: DESY/ Kogler

Artistic visualization of the Higgs Boson and its quantum effects.

New analysis involving Quantum Universe researchers determines the Higgs boson’s lifetime to about 10% precision — something the Large Hadron Collider cannot measure directly.

A research team from the Gfitter group, with key contributions from researchers at the Cluster of Excellence Quantum Universe at Universität Hamburg, has made a new determination of how long the Higgs boson exists before it decays. The result gives a lifetime of about 1.61 × 10⁻²² seconds, with a precision of around 10%.

Instead of a direct measurement at the Large Hadron Collider (LHC), the researchers combined measurements from different experiments and used the relationships between particles predicted by the Standard Model of particle physics.

Using the Standard Model as a precision test

The Standard Model describes known elementary particles and their fundamental forces. Because quantum effects link these particles, precise measurements of some properties can be used to predict others. This is the basis of the global electroweak fit. “Electroweak” describes the closely related electromagnetic and weak nuclear forces, the latter involved in processes such as radioactive decay. The fit compares precise measurements with Standard Model predictions.

For the new analysis, the Gfitter group combined electroweak measurements from the LHC and earlier experiments with the latest theoretical calculations. Researchers from Universität Hamburg, DESY, CERN and the University of Pittsburgh contributed.

A lifetime too short to measure directly

The Higgs boson exists for roughly 1.61 × 10⁻²²  seconds before it decays. In that time, light does not even cover a thousandth of the distance between the proton and the electron in a hydrogen atom. Particle physicists express this fleeting existence as the particle's "width": a larger width means a shorter lifetime. For the Higgs boson, this quantity is far too small for LHC detectors to resolve directly, which means the width cannot simply be read off from the data.

The width can reveal new physics: if the Higgs boson also decays into undetected particles, dark matter, for example, it would decay faster than the Standard Model predicts. But the production and decay rates measured at the LHC always mix the width with the Higgs boson couplings, so neither can be read off on its own. Adding precise electroweak data to the ATLAS and CMS Higgs measurements untangles the two. The result, a width of 4.08 MeV or a lifetime of 1.61 × 10⁻²² seconds, is precise to about 10% and agrees with the predicted value of 4.10 ± 0.06 MeV, without strong assumptions about how the Higgs boson interacts.

“Rate measurements alone leave a blind spot, and the electroweak data fill it in,” says Dennis Schwarz, postdoctoral researcher at DESY.

Finn Labe, also a postdoctoral researcher at DESY, adds: “The information was already there, in measurements that exist. It just had to be combined in the right way.”

The same analysis also places limits on Higgs bosons decaying into particles that cannot be detected. Without assuming anything about the Higgs interactions, the researchers find that fewer than 17% of Higgs bosons can decay into invisible or otherwise undetected particles.

Where could new physics still hide?

The study also investigates where physics beyond the Standard Model could still be hiding. Rather than testing one particular theory, the researchers use a framework called Standard Model Effective Field Theory (SMEFT). It provides a way of describing small effects that unknown, very heavy particles could leave in today's precision measurements.

“The space left for new physics keeps getting smaller,” says Yannick Fischer, a doctoral researcher at Universität Hamburg who worked on the SMEFT approach for his PhD thesis. “But the regions that remain are exactly the ones that the next generation of experiments will be able to reach.”

Future experiments could make these tests even more precise. The researchers discuss the potential of a future electron-positron collider, such as the proposed FCC-ee, where many relevant quantities could be measured around ten times more precisely.

For now, the new Gfitter result shows how much can be learned by bringing existing measurements together: even a particle whose lifetime is far too short to observe directly can be pinned down through the precise web of relationships between the particles of the Standard Model.