Tuesday, February 3, 2015

Higgs Boson Found! Now What? (1/25/15)

Last Sunday's program was a doozie! My guest was Dr. Flera Rizatdinova from the physics department at OSU. Flera analyzes data from the Large Hadron Collider (LHC).

So we were talking about particle physics and it went long - very long. It's good though, because there were lots of questions. I think particle physics is really fun to think about.

When you hear an explanation in particle physics and it feels like you don't understand it, that's probably because it's very weird how things work on the smallest scales. Fundamental particles don't behave like things we're used to. Particle physicists understand all the mathematical models that describe particle behaviors. Yet even they seem to have trouble describing what's "really" going on.

So with that in mind, I'll take a stab at summarizing the program. We started with a sneak peek at my new song and video "Quarks and Electrons." Then I tried to give a quick summary of the Standard Model of Particle Physics. 

I tried to give a quick overview of the Standard Model of particle physics. There were lots of questions!

Basically Quarks (up and down, held together by gluons) and Electrons are the fundamental particles that make up regular matter - all the stuff you and I can touch or see. The Quarks and Leptons have mass. The Gauge Bosons, including Photons and Gluons, cary forces. The Higgs Boson gives other particles their masses.

Here's a chart. It's something like the periodic table of elements, only everything here is a fundamental particle, which means that as far as we know it can't be broken down into smaller parts:

Standard Model of Particle Physics
And that's it. If the universe is a giant Lego playset, then these are all the types of Lego bricks we know about. 

However, we also know the Standard Model is missing pieces! 

Until recently we didn't have the Higgs Boson on the chart. We thought it might exist but until we gathered good evidence for it from the LHC (Large Hadron Collider) we didn't know for sure. Now we do.

Other particles are probably missing as well, and we're looking for them next. 

For one thing, there's dark matter. We know it exists because we can observe its effects on galaxies. But from its properties we can tell it isn't made out of anything on the list.

Another problem is gravity. The other fundamental forces have their particles - for example electromagnetic force is carried by photons - but gravity is not accounted for.

And we don't understand a whole lot about exactly how the Higgs Boson gives particles their masses. It's possible there are several different kinds of Higgs Bosons yet to be found.

Physicists have guessed at many ways of extending the Standard Model. (One example is "Super Symmetry.") These hypotheses all include the model as we know it, and add additional particles of different sorts. All of the extended models make mathematical sense, but which one is right? Which one represents the way the world actually is? The only way to tell is to run an experiment. That's where the LHC comes in.

We took a break at this point to remind ourselves that fundamental particles are real. We had a cloud chamber set up to detect them. The chamber is filled with evaporated alcohol. Whenever a particle zips through it leaves a trail of droplets that you can see. We could see lines appear that let us know muons were zipping through. Muons are generated by particles from outer space slamming into our atmosphere - we call those "cosmic rays."

Looking for particle trails in the cloud chamber!

Whew - we are about halfway through the program now! We talked about how the LHC (Large Hadron Collider) at CERN works by slamming protons together at very high energies. The protons plus energy create a whole bunch of new particles. These decay, or fall apart into smaller pieces.

The particles we're looking for, the unfamiliar ones, do not exist long enough for the detector to detect them. Instead we detect the pieces they generate. From those pieces, we have to work backwards to see if we have evidence that one of the new particles was there.

I demonstrated my "photon detector" by taking this photo. The ATLAS detector at the LHC works in a similar way, only it records lots of different types of particles in addition to photons.

This is a very hard problem to solve. The ATLAS detector collects information from millions of particles per second. All those signals are mixed up together. It's difficult to tell one particle from another.

Flera uses computer programs to help her sort through the data. She's part of a large team that includes scientists from all over the world. They each tackle a different piece of that hard problem. Together they can decipher the signals from the ATLAS detector to find out if any exotic particles were created in the proton collisions.

Scientists are still working on the data generated last time the LHC was running. Next time they turn it on it will run at a higher energy. This increases the chances that exotic particles will be formed. It's exciting to think that the new data set may add to our fundamental model of the universe!

Coming up next:

February 8, 2015
Heart Health, Explosive Gas, and Mexican Mollies
With Jennifer H. Shaw, Ph.D., Department of Zoology, OSU
Regulation of hydrogen sulfide in our bodies is important to our health, but how do our cells know exactly how much to make? Find out how some special fish from Mexico can help us understand our own body chemistry!

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