New research reports a value for the Higgs boson’s lifetime and has a small enough uncertainty to confirm that the particle has a short lifetime.
Collaborative research has come to the conclusion that the Higgs boson’s lifetime is obscenely short. Once the Higgs boson has been generated during a particle collision, it lives on for less than a trillionth of a billionth of a second or, specifically, 1.6 x 10-22 seconds.
Until now, experiments have only been able to determine the value Higgs boson’s lifetime or determine this property with a large uncertainty. Now, in this novel study, the CMS collaboration has recorded a value for the particle’s lifetime that has a small enough uncertainty to validate that the Higgs boson does have such a short lifetime.
Possible advancements from measuring Higgs boson’s lifetime
Successfully measuring the Higgs boson’s lifetime has been high on the priority list for particle physicists as with an accurate experimental value of the lifetime, research would be better able to comprehend the full nature of the particle.
As well as this, it would allow particle physicists to determine whether or not the value matches the value predicated by the Standard Model of particle physics. A deviation from the prediction could point to new particles or forces not predicted by the Model, such as new particles into which the Higgs boson would decay.
Overcoming experimental difficulties
However, it was not an easy task to determine the Higgs boson’s lifetime. Firstly, the predicted lifetime is too brief to be calculated directly. A solution to this came in the form of measuring a related property called the mass width, which is inversely proportional to the lifetime and represents the small range of possible masses around the particle’s nominal mass of 125 GeV. However, this too was not an easy task, as the predicted mass width of the Higgs boson was too small to be easily measured by experiments.
The researchers were able to overcome this challenge with the help of quantum physics. In addition to being created with a mass equal or close to its nominal value, a short-lived particle like the Higgs boson can also be generated with a much larger mass than the nominal value, though the odds of this happening are lower.
This effect – and in fact the mass width of the particle as well – is a manifestation of a quantum quirk known as Heisenberg’s uncertainty principle. On top of this, a comparison between the production rate of these large-mass, or “off-shell”, Higgs bosons with that of the nominal or close to nominal, or “on-shell”, Higgs bosons can be utilised to extract the Higgs boson’s mass width and therefore its lifetime.
By examining data collected by the CMS experiment during the second run of the Large Hadron Collider (LHC), specifically data on Higgs bosons transforming into two Z bosons, which themselves transform into four charged leptons or two charged leptons plus two neutrinos, the CMS team has attained the first-ever evidence for the production of off-shell Higgs bosons. From this result, which has only a 1 in 1000 chance of being a statistical fluke.
The researchers obtained a Higgs boson’s lifetime of 2.1 x 10-22 seconds, with an upper/lower uncertainty of (+2.3/-0.9) x 10-22 seconds. This value, the most precise value ever attained, supports the Standard Model prediction and verifies that the particle does have a tiny lifespan.
“Our result demonstrates that off-shell Higgs-boson production offers an excellent way to measure the Higgs boson’s lifetime,” explained CMS physicist Pascal Vanlaer. “And it sets a milestone in the study of the properties of this unique particle. The precision of the measurement is expected to improve in the coming years with data from the next LHC runs and new analysis ideas.”