A new exotic particle has been hiding out amidst the gobs of data collected by the world's largest atom smasher, physicists have discovered.
The new particle, called Ds3*, is a meson — a type of unstable particle made of one quark and one antiquark. Quarks are subatomic particles and are the most basic building blocks of matter that make up protons and neutrons. They're held together by the strong interaction, or strong force, that is one of the four fundamental forces in nature. (Electromagnetism, weak interaction and gravity are the other three.) No stable form of matter would exist without the strong interaction holding it together.
To find the new particle, Tim Gershon, a professor of physics at the University of Warwick in the United Kingdom, and his team used the Dalitz plot analysis. The technique involved waiting for the particle to decay into its most basic elements (quarks) and tracking their motion inside the Large Hadron Collider (LHC), the world's largest atom smasher.
This is the first time the technique has been used on data from the LHC, located in a 17-mile-long (27 kilometers) underground tunnel on the border between France and Switzerland. The analysis is possible because physicists now have enough experience with the LHC data and can use it for more complicated analysis. Gershon said there could be even more new particles hidden in the data. [7 Strange Facts About Quarks]
"What we've shown here is that we can use the existing data to discover new particles," Gershon told Live Science. "Hopefully, we've opened a door to a whole new era of these types of studies."
An unusual particle
Quarks come in six different flavors known as up, down, strange, charm, top and bottom, and all six have their own antimatter counterpart called an antiquark. The Ds3* particle is made of one charm antiquark and one strange quark. Quarks also have certain degrees of spin that describe how fast they're moving. Properties like the spin and mass of quarks determine the particle that they fuse together to create. The Ds3* particle is the first particle discovered with a spin of three that contains a charm quark. Its properties make it a highly predictable particle, and Gershon said that's why it's the perfect candidate for studying strong interaction.
Strong interaction is perfectly understood in principle, but physicists have yet to solve the equations that describe it, Gershon said. Strong interaction is such a powerful force that it accounts for more of the mass in an atom than the quarks themselves. The equation behind the force is incredibly complex. Physicists and mathematicians have grappled with it for years, and now, the most sophisticated computers are trying to crack it. The new particle could get scientists closer to solving the equation, Gershon said. [Images: The World's Most Beautiful Equations]
Solving the equation involves figuring out the relationship between a lattice of points of space and time. The idea is to calculate the effects of the interactions between these points. But the force is so strong that the equation has proved unsolvable so far. While calculations have gotten much better, scientists need a benchmark to tell if they're going in the right direction.
"The new particle is more and less perfect for that purpose," Gershon said.
The particle's three spin and inclusion of a charm quark mean it behaves in a predictable way in a lattice, and it's easy to track. Scientists can use the measurements of the new particle and compare it with what they've predicted for the interactions, to see if they're on the right track, Gershon said.
The new particle could also reveal more about the gaping difference between the amount of matter and antimatter in the universe. Antimatter has the opposite electric charge of regular matter, and after the Big Bang, matter and antimatter exploded into the universe in equal amounts, physicists think. But antimatter is rare, and physicists are not sure why matter came to dominate the cosmos. Some think the answer may lie in particles that physicists have yet to discover. These particles, they predict, don't fit inside the realm of the standard model of physics — the laws that govern the universe as scientists understand it so far.
"New mesons don't teach us about extensions of the Standard Model [of physics]," Gershon said. "However, this same technique could be used to search for new particles and sources of asymmetry that are not included in the Standard Model," Gershon added, referring to the asymmetry between the amount of matter and antimatter in the universe.
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