Physicists get closer to the extremely short lifespan of the Higgs boson

1.6 x 10-22 seconds: this is, according to theory, the lifespan of the Higgs boson, one of the most sought-after particles in the subatomic world. This time is so short that tens of billions of Higgs bosons could live and die before the light from the device you are using to read this reaches your eyes.

Physicists focus on this life in the real world. By studying data from CERN’s Large Hadron Collider (LHC), scientists have reduced the lifespan of the Higgs to something around 1.6 x 10-22 figure. Scientists were able to do this using data from CMS, one of the LHC detectors. Their work is a major breakthrough, and it’s a sign that, nearly a decade after the discovery of the Higgs boson, there is still a lot to learn about the particle.

“It’s a good achievement, an important step, but it’s only the first step,” says Caterina Vernieri, a particle physicist at the SLAC National Accelerator Laboratory in California, who has worked with the CMS group in the past but no ‘was not involved in this ongoing research.

The Higgs boson is the reason why many particles have mass, to sum up a long history involving complex concepts called “quantum fields” and “symmetry breaking”. It was first theorized in the 1960s – its namesake is Peter Higgs, a British Nobel Prize-winning physicist – but has eluded scientists for decades.

Shattering particles together at increasingly higher energy was key to his discovery, made possible by the LHC, where particles rotate through a 27 km long ring on the Franco-Swiss border. The LHC went online in 2008. In 2012, physicists working there found the fingerprints of something that could were the Higgs boson; by the end of 2013, they had determined that their results were not just random statistical noise.

The search for the Higgs boson was over. But just because scientists have discovered a particle – or anything else – doesn’t mean they understand all of its properties.

[Related: Inside the discovery that could change particle physics]

Theoretical physicists predicted many properties of the Higgs boson in the decades before its discovery. If these theoretical predictions matched what scientists ultimately found, then that would be further evidence that the Higgs boson fits into the theory behind modern particle physics – the so-called Standard Model. It would help scientists learn more about how the universe works on the smallest scales.

But scientists are trying to study things that are not exactly revealed to the world. Particles like Higgs, in addition to their small size, might only show themselves for extremely short periods of time before breaking down into a deli board of other particles.

“The lifespan of the Higgs boson is extremely short,” explains Vernieri. “So when it’s produced in our experiment, we don’t really measure the Higgs boson or see a Higgs boson, but what we do see are the debris … particles that it decays into. “

The CMS scientists therefore looked at the data from the LHC experiments undertaken between 2015 and 2018. By examining the particles in which the Higgs boson disintegrated, they were able to go back and find a range of masses than the boson. de Higgs might have. Thanks to a quantum property called the uncertainty principle, this range is inversely proportional to the lifetime of the particle, which allows physicists to calculate the latter from the former.

According to their calculations, the lifespan of the Higgs boson is somewhere between 1.2 x 10-22 seconds and 4.4 x 10-22 seconds. This is the most accurate estimate of the Higgs boson’s lifespan to date, aligning well with the 1.6 x 10-22 number that theorists predicted.

And, yet, it is not precise enough for some physics.

It is possible, for example, that there is a strange, currently unknown, exotic particle in which the Higgs boson is decaying, which the Standard Model ignores. This would influence the lifespan of the Higgs boson, but so subtly that even this calculation couldn’t detect it.

“It would be a very small change in lifetime value,” explains Vernieri. “So we really have to measure the service life with very good precision.”

Fortunately, particle physicists believe there is room for improvement in this regard. “Measurement accuracy is expected to improve in the coming years with data from upcoming LHC runs and new analysis ideas,” says Pascal Vanlaer, physicist at CMS and one of the physicists behind the project, in a press release.

The first of these next runs is, according to plan, not too far into the future. Since 2018, the LHC has been shut down for a long period of time, rightly called Long Shutdown 2. During this time, the collider and surrounding facilities at CERN have undergone a series of upgrades. Following a disruption to this schedule caused by COVID-19, the collider is currently expected to relight in February 2022.

And there are a lot of other things about the Higgs boson that we still don’t know for sure – from how it is produced, to how it reacts to other particles, to how it interacts with itself. To determine these characteristics, even the LHC may not be sensitive enough.

“We produce a Higgs boson every billion collisions at the LHC,” says Vernieri, and often trying to see Higgs bosons means having to look through a whole sea of ​​other particles. “It’s a very difficult environment to study, very precisely, the production of particles. “

The key will be a cleaner environment to study the Higgs boson with greater precision, Vernieri says. It may then be a job for one of the proposed successors to the LHC.

About Roberto Frank

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