International Scientists Race to Discover Elusive Top Quark
Author James Joyce did not have theoretical physics in mind when he wrote “Finnegan’s Wake” and originated the word quark.
Quark, quite neatly, rhymed with the word mark and helped set the tone in a phrase of the lyrical novel considered by many critics to be a 20th-Century literary masterpiece.
But Nobel physicist Murray Gell-Mann of the California Institute of Technology also liked the word. So he borrowed it from Joyce about a quarter of a century ago to describe theoretical, infinitesimally small constituents of matter.
And the hunt began. An international search over the years has turned up strong evidence for the existence of five quarks, and a Nobel Prize may be waiting for the physicist or team that finds the last but most elusive “top” quark.
“It’s both a competitive and cooperative effort to find this quark,” particle physicist Burton Richter said in an interview.
Richter, who serves as director of the Stanford Linear Accelerator Center in Palo Alto, shared the Nobel Prize for physics in 1976 with Samuel Ting of the Massachusetts Institute of Technology for identifying the “charming” quark.
“This is a very important particle to turn up,” Richter said of the top quark. “So everybody goes hunting but none of the hunts has turned it up definitively.”
Even though there is more than one kind of quark and quarks can be seen only after the collision of subatomic particles traveling near the speed of light in particle accelerators, scientists say they can tell one quark from another.
“You would have no trouble distinguishing the top quark from the bottom quark because the top has a greater mass,” said high energy physicist Klaus Lackner of the Los Alamos Laboratory in New Mexico.
“Looking back at history, though, it’s surprising that it wasn’t found shortly after the bottom quark was found,” he said.
Scientists believe that once the top quark is found, some of the fundamental secrets involving the creation of the universe will begin to unfold.
“We have a strong belief that there are six quarks and six antiquarks and this is based on our beliefs about the symmetry of nature,” said Drasko Jovanovich, emeritus director of the Physics Department at the Fermi National Accelerator Laboratory in Batavia, Ill.
Jovanovich noted that people, the Earth, stars--all constituents of the universe--even the letters of this sentence theoretically have quarks as their most elementary units in the atoms of which they are comprised.
“Quarks played a role at the beginning of time and launched the evolution of the universe,” Jovanovich said. “A great fundamental question for us now is, ‘Why are there only six quarks? Why not eight or 12?’
“By finding the top quark and perhaps understanding why the number is six, maybe then we will begin to understand some rule of nature which somehow is important in the creation of the universe.”
Theoreticians from the European Center for Nuclear Research (CERN) in Geneva reported at the recent annual meeting of particle physicists at Stanford that they have caught a glimpse of the top quark.
CERN’s researchers also three years ago reported evidence pointing to possible, imminent discovery of the top quark, but physicist Ludwig Dobrzynski claims CERN scientists now “have five times as much” evidence.
Richter is not impressed, noting that he missed the meeting and emphasized that if the top quark is found it most likely will be identified by physicists at Stanford.
“I say give us a year to a year and a half and we’ll tell you if it’s there or not. It may be a Christmas present in 1987,” Richter said.
CERN physicists, however, are basing their optimism on an experiment dubbed UA-1 conducted in the Super Proton Synchrotron, a colliding particle beam that runs under the French-Swiss border.
By crashing beams of protons into antiprotons, quarks can be revealed in the shower of particles released in the collision.
Similar experiments provided evidence supporting the existence of the other five “flavors” of quarks--as theoreticians like to call them--up, down, strange, charm and bottom.
Fundamental Units
The unusual names inject a bit of levity into the lofty theoretics involving the minute particles inside the nucleus of atoms, the most fundamental units of all matter.
Quarks supposedly are confined within the neutrons and protons that make up the nuclei or core of atoms and have fractional charges of one-third or two-thirds of the basic charge of the proton or electron of the atom.
Although the nucleus occupies only a tiny fraction of an atom’s total volume, it accounts for almost all of its mass.
The race to find the sixth quark is being carried out in research centers around the world including several in the United States alone. German scientists had hoped to find it with their PETRA ring, but the top quark apparently has a mass higher than what can be achieved with that machine.
Physicists in Japan recently commissioned construction of a high-energy collider they think may produce the elusive particle.
