Higgs boson excitement: Almost palpable (+video)
Scientists hope to report the discovery of the Higgs boson particle by the end of 2012. Such a discovery would help explain the composition of the universe.
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The Standard Model also includes particles dubbed bosons, which carry nature's four basic forces.Skip to next paragraph
In Pictures The Large Hadron Collider
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The best-known boson is the particle of light, the photon. It carries the electromagnetic force, which is responsible for such everyday phenomena as the scent of a rose and the pull of a magnet.
Another boson is called the gluon. It binds together the quarks that constitute protons. Without gluons, quarks would stick together no better than an undercooked soufflé, atoms would not exist, and neither would stars, planets or life.
Particle accelerators such as those at CERN and Fermilab methodically discovered all the particles predicted by the Standard Model except one.
The hold-out is the Higgs boson, and its refusal to show itself has long frustrated physicists. The Higgs particle is needed to complete and validate the Standard Model, since if it turns out not to exist scientists would have to figure out the constituents and mechanics of the universe from square one.
Just as importantly, the existence of Higgs was postulated in 1964 to serve a crucial function: conferring mass on some particles that would otherwise have none. Technically, the Higgs particle itself does not provide mass; the particle is, instead, a little knot of matter squeezed out of a force field like a curd forming in soured milk.
The force field is called - of course - the Higgs field.
The Higgs field gives mass to some particles but leaves others alone, in a process one might compare to making cotton candy. As the wand is passed through the gossamer cloud of spun sugar, it holds onto more and more of the pink strands.
In much the same way, particles passing through the Higgs field picked up more and more mass, until they became the quarks and leptons and bosons that constitute the stuff of today's cosmos. In this analogy, some wands are oiled, preventing sugar from sticking; these particles remain without mass. Other wands are super-sticky, picking up more than their fair share of mass.
The particle is named after Peter Higgs, now 83, of the University of Edinburgh in Britain, but five other physicists came up with the same idea almost simultaneously.
"The God Particle" was the title of a 1993 book by Leon Lederman, a Nobel-winning physicist and former head of Fermilab, and science writer Dick Teresi.
The publisher vetoed titles with "Higgs" or anything else too esoteric. Lederman later said he wanted to call the book "The Goddamned Particle" because the Higgs was so elusive.
Fermilab began its Higgs quest 10 years ago, using its four-mile (6.4 km) circumference Tevatron to smash together protons and their anti-matter twins, anti-protons. When matter meets anti-matter, the two annihilate, leaving behind pure energy.
Out of that energy crystallize new particles. It was in this debris that the Tevatron scientists sought evidence of the Higgs boson.
Because the Higgs is hypothesized to exist for a mere fraction of a second before decaying into other particles, the strategy was to look for these "daughter" particles.
CERN's 16.7-mile (27 km) circumference LHC, which smashes protons against protons at nearly the speed of light, looks for two high-energy photons. The Tevatron looked for two bottom quarks. Before budget cuts forced it to shut down last September after trillions of proton-anti-proton collisions, it found as many as 1,000 pairs that could have come from Higgs particles.
"It is a real cliffhanger," said physicist Gregorio Bernardi of the Nuclear Physics Laboratory of High Energies in Paris and leader of one of the Tevatron experiments. "We know exactly what signal we are looking for in our data, and we see some evidence for the production and decay of Higgs bosons in a crucial decay mode with a pair of bottom quarks. So we are very excited."
The Tevatron results indicate that the Higgs particle has a mass between 118 and 132 giga-electron volts (the unit of mass-energy used in physics in which 1 GeV is about the mass of the proton). Last year, the LHC pegged the mass at between 115 and 127 GeV.
(Additional reporting by Sharon Begley and Chris Wickham; Writing by Sharon Begley; Editing by Will Dunham)