SYDNEY: Two new subatomic particles have been found by recreating conditions at the beginning of the universe, according to a new international study.
The particles are exotic relatives of the proton and neutron.
“These particles, named Sigma-sub-b, are like rare jewels that we mined out of our data,” said Jacobo Konigsberg of the University of Florida, a spokesperson for the project.
The team of physicists at the Fermi National Accelerator Laboratory in Illinois, USA, fired protons and antiprotons (which have the same mass as protons but opposite charge) at each other at close to the speed of light.
This allowed them to reproduce the strange matter that was abundant in the ultra-high energy conditions moments after the Big Bang.
After creating billions of these subatomic car crashes, the researchers observed just 240 of the rare Sigma-sub-b particles.
In the collisions, the energy of the speeding protons was converted into mass (in accordance with Albert Einstein’s famous equation E = mc2), however the particles decayed in a fraction of a second.
“It’s amazing that scientists can build a particle accelerator that produces this many collisions, and equally amazing that the collaboration was able to develop a particle detector that can measure them all,” said co-spokesman Rob Roser, of Fermilab.
The particles are part of the baryon family of subatomic particles, which includes protons and neutrons. Baryons are made up of three quarks, one of the fundamental building blocks of matter.
The term ‘baryon’ comes from the Greek word ‘barys’, meaning ‘heavy’, because when the term was created, it was believed that members of the baryon group were heavier than other types of particles.
The two new particles are the heaviest baryons yet found – six times heavier than a proton – making them weightier than a complete helium atom, which has two protons.
“These newest members of [the baryon] family are unstable and ephemeral, but they help us to understand the forces that bind quarks together into matter,” said team leader Petar Maksimovic of Johns Hopkins University in Baltimore, Maryland.
Normal matter around us, including protons and neutrons, is made up of only two types of quarks, called ‘up’ and ‘down’ quarks. In total there are six types of quarks – up, down, strange, charm, bottom and top.
Of the new particles, 103 were positively charged and made of two up quarks and one bottom quark, while 134 were negatively charged particles made of two down quarks and a bottom quark.
“Little by little, we are compiling an ever-clearer picture of how quarks build matter and how subatomic forces hold quarks together and tear them apart,” said Maksimovic.
The discovery has confirmed theorists’ predictions of the existence of Sigma-sub-b particles and has helped to complete what the physicists call the periodic table of baryons.
“We are confident that our data hold the secret to even more discoveries that we will find with time,” said Roser.