My guest blogger today is Joe Bochenek, a Ph.D student at Florida State University. He is working at CMS, one of the experiments at the Large Hadron Collider, located on the border between Switzerland and France.The LHC announced observation of a new particle on July fourth.
Stephanie--Joe, what can you tell us about the amazing discovery that has taken place at the LHC?
|Large Hadron Collider|
Joe--The exciting thing about the LHC is that it is on the absolute boundary of human knowledge about nature. There is a theory called the Standard Model of Particle Physics that describes all of the matter that we know about, from stars to the particles that make up a new born baby, to more exotic forms of matter. Everything we have observed experimentally fits in to this eloquent mathematical framework, and this framework can be used to make predictions to fantastic accuracy.
The only problem is that the framework, by itself, is incomplete - it has a mathematical inconsistency. To fix this, some very smart theoretical Physicists, including Peter Higgs, proposed an addition to the theory. This addition is called the Higgs field (keep this distinct in your mind from the Higgs boson, which is related but not the same). The Higgs field "fixes" the standard mode so that the Standard Model gives us everything: a theory that describes all that we have seen in experiments over the last 100 years or more, and complete mathematical consistency. But if we include this modification to the theory we get some extra baggage, and that baggage is called the Higgs boson.
The Higgs boson is a particle predicted by the Standard Model if we include the Higgs field -- it MUST exist if the Higgs field exists, so we should be able to see it in our experiments. No Higgs particle, no Higgs field, no consistency, and thus our theory is wrong, and there must be something else that we don't know about or haven't been clever enough to think up.
Electromagnets at the LHC
However, on July 4th the world saw evidence for a particle that is consistent with a Higgs boson. If, upon further scrutiny, it turns out to be the Higgs field, then the theorists who proposed it 50 years ago will be very happy.
Then again, it could be something else. It could be something that is imitating the Higgs field, or it could be a brand of Higgs boson a bit different from the one predicted. In either case it would mean that there is more in nature than our theory tells us. But this is actually a good thing because we can use this new particle, whatever it is, to try to determine the real theory that explains everything. That is, at least if we're wrong, we have a lead. When we have more data we will be able to measure the properties of this new particle and better determine if it is a Higgs boson, or if not, we can see more clearly what it is.
Now I should mention that Cosmological experiments tell us that normal matter -- quarks, electrons and the other particles described by the standard model -- only make up 4% of the universe. The rest of the universe is comprised of so-called "dark matter" and "dark energy".
We don't know ANYTHING about this stuff, but we can see that it is there by the way stars move around each other. So even if the particle we observe is a Standard Model Higgs boson, and the Standard Model is shown to be right, we still have a lot to learn about the universe, and we hope that we can catch some hint of what is out there using the LHC, in concert with other experiments.
Also, we know that even if we have found the Higgs, that the standard model doesn't explain gravity. So there are many problems left unsolved. But that is the nature of pure science: you don't know what you will find until you look. You don't know what will be the windfall a particular experiment, either technologically, scientifically or just in terms of human edification, until you look over that next mountain. Or maybe you won't find anything at all (of course, we're pretty sure we would find something otherwise we wouldn't have built the experiment and dedicated many sleepless nights to making it work). And so the observation of this new particle at the LHC is very encouraging.
I think this is a good video explaining the Higgs better than I could (and the artwork is cool):
Or for something less colorful, here is the CERN press release from July 4th:http://press.web.cern.ch/press/PressReleases/Releases2012/PR17.12E.html
Stephanie--Joe, thank you for your explanation. I think I understand a little more about this fascinating subject. Keep us up to date on any new discoveries.