Curious extra Higgs particles could explain W-boson with high mass

Recently, it turned out that the W boson is probably heavier than assumed. To explain the shocking measurement, physicists have invented all kinds of exotic new particles, including technicolor and glue ball Higgs particles.

On April 7, researchers unveiled a new analysis of measurements taken with the now-retired Tevatron particle accelerator near Chicago. Their work showed that the mass of the W boson is greater than the standard model of particle physics predicts. It was a shocking result that suggested the existence of as yet unknown particles. Several ideas have since been raised about such new particles.

The W boson is one of the particles that transmits the weak nuclear force. In addition, the W boson plays a role in interactions between neutrinos and other subatomic particles.

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Prior to the Tevatron analysis, all mass measurements of the W boson gave a value of about 80,379 giga-electron volts. However, the new analysis yields a mass of 80.4335 giga-electron volts. The difference with the old value has a statistical significance of 5 sigma. This means that if the old value is correct, there is a 1 in 3.5 million chance that this new value was found by chance. After a decade of data analysis from the Tevatron team, this is one of the most accurate particle measurements ever.

Extra Higgs particles

The remarkably high mass of the W boson indicates that the standard model of particle physics is wrong at some point. This is in a way shocking because the standard model so far has been extremely accurate in its predictions. On the other hand, it is not necessarily surprising, for we already thought that the theory is incomplete. For example, the standard model does not explain dark matter or the excess of matter relative to antibody in the universe. The model can not even explain gravity.

Also read: ‘Too heavy’ W-boson could turn particle physics upside down

Since the release of the Tevatron results, particle physicists have produced several articles explaining how to modify or expand the standard model to account for a heavier W boson. “We find it surprisingly easy to tailor the model to this difference,” says particle physicist Ramona Gröber of the University of Padua in Italy. “In previous cases, it was much harder to explain abnormal measurements.”

Many of the proposed explanations involve the addition of an extra Higgs boson. It is the fundamental particle that belongs to the Higgs field, the field that supplies particles like the W boson with mass. “Even a simple change like adding another Higgs boson can explain the observed value,” said particle physicist Ashutosh Kotwal of Duke University in North Carolina, who was part of the Tevatron team. ‘There are good and simple solutions. I find the simplest the most exciting. ‘

Technicolor and glue ball

The various additional Higgs particles that have been proposed have all sorts of properties where they differ from the well-known Higgs particle. Some have an electric charge where the regular Higgs boson is neutrally charged. Others consist of even smaller particles. In some models, these are known particles, eg gluons, which together form a so-called glue ballforms higgs particles. In other models, these building blocks are also new particles in themselves, such as so-called techniquarks, which together form a ‘technicolor Higgs particle’. In all these models, the new Higgs particles are accompanied by new fields, which give the W-boson extra mass.

Many of the proposed models also attempt to answer other open-ended questions in particle physics. For example, there is a popular model that takes into account the extra mass of the W boson by adding a new type of particle, leptoquark. That leptoquark could also explain another major mystery in particle physics: the ‘g – 2 deviation’ of muons, which arises from the fact that muons appear to spin faster than the standard model predicts. In addition, some of the proposed particles could also be the particles that make up dark matter.

supersymmetry

Sometimes even a number of possible new particles are suggested. For example, supersymmetric particles, also called particles called, offers a single explanation for a heavier W boson, the g-2 aberration of muons, and the mystery of why elementary particles generally have the mass they have.

Read also: Mysterious muons: supersymmetry or calculation errors?

“We expect the new particles predicted by the theory of supersymmetry to be slightly heavier than the Higgs boson,” said particle physicist Peter Athron of Monash University in Australia. In terms of mass, the Higgs boson is at the upper limit of the particles that the Large Hadron Collider (LHC), the largest particle accelerator in the world, can create. This would explain why we have never observed supersymmetric particles.

Premature

Reviewing all the ideas takes a lot of time, experimentation and in some cases a new generation of particle accelerators. “Just a new mass of the W boson will not be enough to choose a new theory of nature,” says physicist Francesco Sannino from the University of Southern Denmark.

But before physicists look for new particles and a new theory of nature, they will have to double-check the Tevatron measurements. “It is too early to think about new physics at this point before we find out why this measurement differs from other measurements,” said particle physicist Matthias Schott of the CERN Research Institute near Geneva, who was working on a previous W-boson measurement with LHC. “New particles provide a much cooler explanation, of course, but all the other measurements of the mass of the W boson fit together perfectly, and only this measurement does not fit.”

Schott and his colleagues at CERN have already begun comparing the new measurement with data from the LHC. According to Schott, they should have results within the next six months to two years. It depends on these results whether the pursuit of new physics can continue.

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