The Large Hadron Collider is the largest particle accelerator in the world, and physicists using this massive machine have recently detected a rare subatomic process which could have significant impact on the field of particle science.
A Bs particle, made up from a bottom antiquark and a strange quark, was seen decaying into two muons. A similar process was observed taking place in a Bd particle, made up from a down quark and a bottom antiquark. This process was predicted to take place roughly four times out of every billion particles in Bs mesons, a ratio close to that measured by the pair of experiments.
Quarks, which make up some subatomic particles, have odd names, such as top, bottom, up, down, and strange varieties. Those containing bottom quarks tend to be long-lived, are produced in large numbers, and are easy to detect, making them a target for many particle physicists.
The Standard Model of physics is a widely accepted theory of how subatomic particles behave in the universe around us. However, this system of ideas does not address several findings in physics, such as the relative abundance of matter over antimatter we see around us, or the presence of dark matter. These shortcomings have driven many physicists to search for other theories which could explain the ultimate building blocks of matter. Correlation between the observed decay rate and that predicted by scientists could eliminate some new theories, and provide more evidence the standard model is correct.
"Many theories that propose to extend the Standard Model also predict an increase in this Bs decay rate. This new result allows us to discount or severely limit the parameters of most of these theories. Any viable theory must predict a change small enough to be accommodated by the remaining uncertainty," said Joel Butler from Fermilab, America's particle physics research laboratory in Illinois.
The odd Bs mesons studied during these experiments at the LHC continually oscillate between existing as matter and antimatter. Analysis of these particles could help answer one of the greatest questions in cosmology. After the universe cooled following the big bang, matter and antimatter should have been created in equal masses, annihilating itself, leaving behind nothing but energy. However, the stars, planets, and galaxies all around us are composed almost exclusively of ordinary matter. Astrophysicists are uncertain why this is the case.
Discovery of the rare decay was seen in the results of experiments conducted at the collider before it was shut down for upgrades.
"The LHC will soon begin a new run at higher energy and intensity. The precision with which this decay is measured will improve, further limiting the viable Standard Model extensions. And of course, we always hope to see the new physics directly in the form of new particles or forces," Butler said.
Analysis of the rare particle breakdown, examined from a compilation of the two experiments, was published in the journal Nature.
