A massive problem
What is mass and why are some particles more massive than others?
Seems like a really obvious question, doesn't it? Mass is the amount of matter in something. You know a rock has mass because it has inertia: it resists changes in its motion. If it's in a planet's gravitational field, it will have weight. And if it's a really big rock, it will exert a measurable gravitation pull on other masses nearby. Easy. Next question?
A view along a section of the 27km long LHC tunnel and collider
But hang on a minute. That's describing the "symptoms" of mass. It isn't explaining what mass is. It's a bit like describing the symptoms of a cold without talking about the virus that's causing it. The total mass of an object consists, ultimately, of the sum of the masses of all the sub-atomic particles it is made of. So what gives these particles mass? And why do some particles, like photons have no mass to speak of while others, like top quarks, have large masses? How do they "know" how much mass to have?
In other words, what makes stuff stuff?
For this assignment, you will research the latest scientific thinking about mass and how the experiments at the LHC might make or break the theory. Your teacher will tell you how they would like you to present your findings.
Key things to find out:
- What are the masses of the fermions (quarks and leptons) in the Standard Model?
- Why do particle physicists express these masses in electronvolts (eV), a unit of energy, instead of the normal SI unit of mass, the kilogram (kg)?
- What is the Higgs mechanism?
- When did Professor Peter Higgs first postulate the Higgs mechanism?
- What are the predicted possible masses of the Higgs boson?
- What are the predicted decay products of a Higgs boson?
- Assuming it exists, why haven't particle accelerators made a Higgs boson yet?
- If it does exist, why are physicists so confident that the LHC experiments will find it?
- Can you find a simulation of the decay signature of a Higgs boson?
Useful online references:
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