A particle detector helps scientists study subatomic particles. Physicists at the Fermi National Accelerator Laboratory in Batavia, Ill., use this detector to record information about particles produced in collisions between beams of protons and beams of antiprotons.
Credit: Fermilab Visual Media Services

Particle physicists are buzzing about a hefty discovery. In April 2022, researchers at the Fermi National Accelerator Laboratory (also known as Fermilab) announced that a particle called the W boson appears to have slightly more mass than expected. Their results were published in the journal Science.

Bosons are particles that transmit forces between other particles. As particles go, bosons are much less popular than their cousins the fermions, which make up matter. The W boson carries the weak nuclear force, which is involved in the decay (breakdown) of some radioactive atoms.

A particle accelerator helps scientists study electricity and the building blocks of matter. The accelerator at the Fermi National Accelerator Laboratory in Batavia, Illinois, accelerates protons to almost the speed of light in an underground tunnel, shown here.
Credit: Fermi National Accelerator Laboratory

So who cares about a chunky boson? Physicists do. Modern physics is based largely on a theory called the Standard Model. The Standard Model includes a family tree of particles and can be used to make predictions about their properties. Most of these predictions have turned out to be highly accurate. A deviation in the mass of the W boson, if confirmed, could hint at the existence of unknown particles or other revisions to the Standard Model.

Physicists study particles in giant devices called particle accelerators. As the name suggests, these devices accelerate particles to extremely high speeds. They then smash them together to study any particles created in the collision.

The experiments in question were conducted in an accelerator called the Tevatron. The device smashed positively charged particles called protons into anti-protons, their antimatter counterparts. About one in 10 million such collisions create a W boson. It took the scientists 10 years to collect enough data.

The Tevatron was shut down in 2011. But it took another 10 years to properly analyze all that data. The results suggest that the W boson is 0.1 percent heavier than expected. That’s about as much as your weight might vary if measured before and after lunch. But for extremely precise particle measurements, it may be just enough to alter our understanding of the universe.

July 5, 2012

Scientists at CERN, Europe’s leading physics laboratory, have announced significant proof of a subatomic particle that may be the long-sought Higgs boson. A boson is any member of a certain class of atomic and subatomic particles. For decades, scientists have searched for the elusive particle, which is believed to give matter its mass. The particle is named for the British physicist Peter Ware Higgs, who posited its existence in 1964.

Mass is an extremely important characteristic of matter. Light is made up of particles called photons, which have no mass. The lack of mass enables photons to move at the fastest possible speed–the speed of light. If the particles that make up matter had no mass, they would also zip across the universe at extremely high speeds. But something provides a drag that prevents matter from doing this, an effect we call mass. Scientists believe that the drag is provided by interactions with Higgs bosons.

The Large Hadron Collider (LHC) smashes together circulating beams of high-energy particles. Scientists use the LHC to improve their understanding of the behavior of subatomic particles (particles smaller than atoms). (© CERN)

Evidence for the newly discovered particle came from two separate experiments being conducted using the Large Hadron Collider (LHC), outside Geneva, Switzerland. The powerful particle accelerator smashes bits of matter together at nearly the speed of light. The LHC scientists will continue working to confirm the results. But the discovery, announced on July 4, has sent ripples of excitement through the scientific community. If the new particle is in fact the Higgs boson, studying it may lead to new answers–and new questions–for our understanding of the nature of matter.

Additional World Book articles:

• Hadron
• Standard Model
• The Dark Side of the Universe (a special report)
• Found—The Top Quark (a special report)
• What Is the Fundamental Nature of Space? (a special report)