April 29, 2012
CERN Particle Accelerator Reveals Previously Unknown Particle
It has not discovered the Higgs Boson -- not yet, anyway -- but the Large Hadron Collider (LHC) particle accelerator has revealed a never-before-discovered particle comprised of three quarks.
The discovery, which was announced Friday by Symmetry Magazine, was made by University of Zurich physicists and was based on data gathered in the CMS detector at the Geneva, Switzerland-based facility, which is overseen by the European Organization for Nuclear Research (CERN).
According to Symmetry reporter Kathryn Grim, the particle was made up of three quarks, one of which was a bottom/beauty quark (a third-generation quark with a charge of –1/3e), and according to a statement released by the university, the baryon, which has been dubbed Xi_b^* or neutral Xi_b^star baryon, "confirms fundamental assumptions of physics regarding the binding of quarks."
"In the course of proton collisions in the LHC at CERN, physicists Claude Amsler, Vincenzo Chiochia and Ernest AguilÃ³ from the University of Zurich´s Physics Institute managed to detect a baryon with one light and two heavy quarks," the university said in their statement. "The particle Xi_b^* comprises one 'up', one 'strange' and one 'bottom' quark (usb), is electrically neutral and has a spin of 3/2 (1.5). Its mass is comparable to that of a lithium atom."
The particle exists for just a miniscule amount of time, and was only discovered by scientists because it leaves behind an "imprint" or a "decay signature" after it disappears, said Connor Simpson of the Atlantic Wire. He also noted that the baryon is very rare and does not exist naturally on Earth. Here, it can only occur within the LHC, though scientists say that is can occasionally be found in outer space.
In an email to Carl Franzen of Talking Points Memo (TPM), Carlos Lourenco, a senior researcher with CERN, said, "Besides helping to understand how quarks bind and therefore further validate the theory of strong interactions, one of the four basic forces of physics, this measurement represents a tour-de-force that opens up good perspectives for future discoveries."
"The calculations are based on data from proton-proton collisions at an energy of seven Tera electron volts (TeV) collected by the CMS detector between April and November 2011. A total of 21 Xi_b^* baryon decays were discovered — statistically sufficient to rule out a statistical fluctuation," the University of Zurich said. "The discovery of the new particle confirms the theory of how quarks bind and therefore helps to understand the strong interaction, one of the four basic forces of physics which determines the structure of matter."
Their findings have been submitted to the journal Physical Review Letters.