First thing's first:
In an eagerly anticipated announcement, physicists at CERN working with the Large Hadron Collider (LHC) have found strong INDIRECT evidence for the existence Higgs boson -- a.k.a., the "God Particle" -- that has been sought for nearly half a century. Finding the Higgs boson, a "massive" particle that arises out of the Higgs field, represents the last of the particles in the so-called Standard Model of particle physics for which empirical evidence (even indirect) has been found and it thus "completes" the model.
Schematic of the various LHC detectors and experiments.
Quoting the July 4, 2012 CERN press release:
"'We observe in our data clear signs of a new particle, at the level of 5 sigma, in the mass region around 126 GeV. The outstanding performance of the LHC and ATLAS and the huge efforts of many people have brought us to this exciting stage,' said ATLAS experiment spokesperson Fabiola Gianotti, 'but a little more time is needed to prepare these results for publication.'
"'The results are preliminary but the 5 sigma signal at around 125 GeV we're seeing is dramatic. This is indeed a new particle. We know it must be a boson and it's the heaviest boson ever found,' said CMS experiment spokesperson Joe Incandela. '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.'"
Simulation of a Higgs boson signature resulting from a proton-proton collision that forms two jets of hadrons and electrons.
The Higgs boson arises out of the Higgs field, a field permeating the cosmos that is necessary to explain how spontaneous symmetry breaking of the electroweak field occurs, thus giving mass to otherwise massless elementary particles such as quarks and leptons that make up fermions. In short, without this field elementary particles would move at the speed of light and would have no mass.
Generations of matter in the Standard Model including fermions with the gauge bosons on the right.
In the same way that the photon arises out of the electromagnetic field as a carrier particle out of that fundamental force -- except it is massless and moves at the speed of light -- the Higgs boson is the equivalent particle that arises in the symmetry breaking of the weak force that, in turn, gives mass to its W and Z carrier particles.
In this case, the massive but very short-lived Higgs boson "slows" things down and "gives" mass to what would otherwise be massless particles. Note that all 3 particles -- the photon and the W and Z bosons -- are ultimately types of electroweak carriers. Again in this case, we are discussing the symmetry breaking of the electroweak field that results in elementary particles (i.e., quarks and leptons) with mass.
Prof. Peter Higgs arrives for the CERN announcement, July 4, 2012. The Higgs boson is named for him.
Don't be freaked out by the term "symmetry breaking" -- it simply refers to the incredibly tiny variations that occur (why is a different question) that cause a particle to have one type of property (mass, charge, or spin) rather than another. Ultimately, it's why the physical Universe exists as it does. Including us.
CERN Director General Rolf-Dieter Heuer and CMS experiment spokesperson Joe Incandela.
Further quoting from the press release:
"We have reached a milestone in our understanding of nature," said CERN Director General Rolf Heuer. "The discovery of a particle consistent with the Higgs boson opens the way to more detailed studies, requiring larger statistics, which will pin down the new particle's properties, and is likely to shed light on other mysteries of our universe."
Here are some links:
The New York Times (single page format): A New Particle Could Be Physics' Holy Grail by Dennis Overbye
The Washington Post: Scientists discover new subatomic particle at the center of everything by Brian Vastag and Joel Achenbach
BBC online: Higgs boson-like particle discovery claimed at LHC by Paul Rincon
But this is no where near the end of the story: The Standard Model still tells us nothing fundamental about gravity. As a result, the Grand Unification of general relativity and quantum mechanics, while theoretically possible through the mathematical elegance of string theory and its larger and more esoteric cousin, M-brane physics, remains as experimentally elusive as it has now for a century. Fundamental knowledge of more exotic creatures such as dark matter -- to say nothing of dark energy -- remain as yet hidden from complete human understanding.
Nor (as I understand it) does the Standard Model tell us anything about why particles have the *particular* mass that they do.
Today's announcement is merly a milestone -- albeit a critical one -- along that ongoing path to true understanding of the Universe (and possibly the multiverse).
And with that, I shall end this entry. And a special thanks to Kristof for helping me with this entry.
Oh, and Happy Fourth of July!!!