Well, it appears that we are there with the Higgs. This is good
enough.
Now we have nailed down the mass it becomes possible to work around
that.
All this took an awful long time, but we had obviously narrowed it
down to the point that such a discovery was close at hand. There is
much more to learn yet, but some of that will come fairly quickly.
In the meantime, all predicted particles from the standard theory
have now been shown to be real.
New Particle at
World's Largest Atom Smasher is Likely Higgs Boson
By Clara
Moskowitz, LiveScience Senior Writer
Physicists are more
than 99 percent sure that they've found a new elementary particle
that is likely the long-sought Higgs boson.
Evidence for the new
particle was reported today (July 4) by scientists from the world's
largest atom smasher, the Large Hadron Collider in Switzerland.
Researchers reported they'd seen a particle weighing roughly 125
times the mass of the proton, with a level of certainty that all
but seals the deal it's the Higgs boson.
"This is indeed
a new particle. We know it must be a boson and it’s the heaviest
boson ever found," Joe Incandela, spokesperson for LHC's CMS
experiment, said in a statement. "The implications are very
significant and it is precisely for this reason that we must be
extremely diligent in all of our studies and cross-checks."
The Higgs, nicknamed
the "God particle" (to the chagrin of many
scientists, who prefer its official name), is thought to hold the
key to one of the mysteries of the universe: Why do things
have mass?
Its discovery
represents a major step forward in our understanding of why the
universe exists as it does, with matter clumping together to form
galaxies, stars, planets and us, scientists say. [Top 5
Implications of Finding the Higgs Boson]
To be absolutely
sure they've made a true new discovery, rather than simply seen a
fluke, physicists wait for enough data so that their statistics
reach a level called 5 sigma, meaning that there is only a one in
3.5 million chance the signal isn't real.
"We observe in
our data clear signs of a new particle, at the level of 5 sigma, in
the mass region around 126 GeV," said Fabiola Gianotti,
spokesperson of LHC's ATLAS experiment. (GeV stands for gigaelecton
volts, a unit of mass roughly equivalent to the weight of a
proton.) Gianotti presented the findings to loud applause from
physicists gathered at CERN (LHC's home facility) to hear the LHC's
results.
The LHC's CMS
experiment saw signs of a new particle with a mass of 125.3 GeV at
a certainty level of 4.9 sigma.
"As a layman I
would now say, I think we have it," CERN director general Rolf
Heuer said during a presentation at the Geneva, Switzerland lab
reporting the results today. "Do you agree?" he asked the
gathered physicists, who responded with loud applause.
The Higgs boson is
the last undiscovered piece of the puzzle predicted by the reigning
theory of particle physics, called the Standard Model. Yet the
model does not predict what its mass is, so physicists have to
search through a wide territory to find it. The researchers can't
yet be absolutely sure that the new particle they've found actually
is the Higgs.
"The work now
is to actually measure its quantum identity (all its quantum
properties)," Caltech physicist Maria Spiropulu, who was in
the audience at the LHC announcement, told LiveScience in an email.
"Then we can say if it THE minimal standard model Higgs or a
Higgs look-alike. We have been propelled to the future of particle
physics towards the understanding of the fundamental properties of
our universe in its entirety."
The LHC is the most
powerful machine on Earth, capable of smashing protons together to
produce huge explosions of energy that transform into new and
exotic particles inside its17-mile (27 kilometer) underground loop.
Yet the Higgs boson is so rare only one out of a trillion of the
collisions inside the accelerator are likely to produce it, and
even then, it decays almost immediately into other particles.
"This is not a
needle in a haystack — it's much worse than a needle in a
haystack," said Joe Lykken, a theoretical physicist at the
Fermi National Accelerator Laboratory (Fermilab) in Batavia, Ill.
Over the past few
years, researchers have been able to exclude certain possible
masses for the Higgs, narrowing the possible window for Higgs
further and further. Just this week, Fermi scientists
announced that data from the largest U.S. particle
accelerator, the Tevatron (which shut down last year), show the
Higgs, if it exists at all, must have a mass between 115 and 135
GeV.
In December 2011,
the LHC teams announced their latest findings, which restricted
the Higgs to a mass between115 and 130 GeV, though with
less certainty than the new Tevatron results.
"This is a
really special time," said Fermilab physicist Dan Green, a
member of LHC's CMS experiment, said Monday (July 2). "I
remember when the top [quark] was discovered 20 years ago. This is
one of the most exciting weeks I've had for a very long time."
[9 Unsolved Physics Mysteries]
Today's findings
come from the two general-purpose experiments at LHC, ATLAS and
CMS. Both observed particle collisions independently and analyzed
their observations separately. In fact, scientists from each team
were not allowed to tell each other what they found until today,
for fear their results would bias the other experiment's
researchers toward looking for the same results.
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