Nicolo Cartiglia -INFN Torino1 Very difficult questions about elementary particle physics Friendly chat at Lucia’s school

Nicolo Cartiglia -INFN Torino2 A very short summary Today

Nicolo Cartiglia -INFN Torino3 What does it mean to study “particle physics” ? It means you want to answer questions like these: If you keep on breaking things up, what is the smallest piece you are left with? Is there another universe where I can go to get away from my homework? Is a black hole going to eat my lunch? We don’t really know, we have not finished smashing our particles.. That is pretty unlikely….even though not impossible I’m afraid not..sorry….

Nicolo Cartiglia -INFN Torino4 How many unbreakable “particles” are there? What do we know about nature? we think 12, however we are still looking for a few missing And how many forces? Gravity Electricity and magnetism A strong force, to keep atoms together A weak force, to make particles disappear So, maybe there are only 4 forces, but maybe 5 or 6..

Nicolo Cartiglia -INFN Torino5 u d c s t b e  e   Problem: Nature uses these 4 particles quark leptons If you are curious, these are the 12 fundamental particles Not sure why they exist…

Nicolo Cartiglia -INFN Torino6 Is it true that anti-matter exists? YES!! We do it all the time, every day of the year…. It turns out that each particle has a “twin inverted sister” with opposite properties LuciaAnti-Lucia

Nicolo Cartiglia -INFN Torino7 A bigger problem…. The rules of nature tell us that the universe should be made of matter and antimatter, equally, however… we have no idea where the antimatter has gone. In short: We have lost 50% of the universe

Nicolo Cartiglia -INFN Torino8 Using an accelerator, you accelerate particles to the speed of light, and then you smash them into each other How do you make new particles? This is my job: I break-up particles and I look at what is produced in the collision.

Nicolo Cartiglia -INFN Torino9 You own some small accelerators at home: Old electric bulbs: electrons fly from the filament to the glass Your old TV (not the flat screen): electron guns shoot electrons at the screen Every time you turn on the light, you make a lot of particles called “photons” small, Medium, Large, Extra Large, and Huge accelerators are in laboratories. They can be many miles long, and they are the most complex machines ever made. The most famous accelerator is the LHC, at the CERN laboratory in Switzerland How big is a particle accelerator?

Nicolo Cartiglia -INFN Torino10 Ladies…The Large Hadron Collider 27 km long…..

Nicolo Cartiglia -INFN Torino11 A time-travel machine Most of the particles we make in accelerators are not present normally in nature, you cannot mail-order any of them… These particles existed just after the beginning of the universe (the BIG-BANG), and then they disappear. So we can say that in our accelerator we are ‘reproducing” what happened just after the BIG-BANG. Larger accelerators go further back in time..

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Nicolo Cartiglia -INFN Torino13 Let’s make a summary before going to CERN (European Center for Nuclear Research) Nature is made of very few particles We don’t quite know the purpose of many of them We make new particles breaking-up old one in particle accelerators Studying particle physics is equivalent to study the BIG-BANG We have lost 50% of the universe Let’s go see the largest particle accelerator ever made…

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Nicolo Cartiglia -INFN Torino15 CERN: A particle speeding track 27 kilometers long, 100 meter underground The Large Hadron Collider. Large is an understatement! Hadrons mean protons. Collide is what it does. Tiny bunches of counter-circulating protons. Colliding head-on 40 million times each second.

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Nicolo Cartiglia -INFN Torino17 Antonaldo Diaferio

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Nicolo Cartiglia -INFN Torino20 What do we want to find at the LHC? Among the many new particles we are hoping to find, one is particularly important: The HIGGS particle The Higgs boson is very heavy and therefore it’s very difficult to create it. We have been trying to find it for the past 20 years, but now we think we can finally do it.. There is one small detail: the theory might be wrong, and the HIGGS boson might not exist.. That would be really embarrassing Mr Higgs

Nicolo Cartiglia -INFN Torino21 We have other unsolved mysteries… Now that we know everything about nature, we can approach more complex problems: - Let suppose the BIG-BANG is the beginning of this universe. What was there before? Why did it start? - Are there OTHER universes? - Are they really only 3 dimensions? Some very serious theories suggest the dimensions are 11…

Nicolo Cartiglia -INFN Torino22 Our biggest problem ever I told you that nature is made of 12 particles plus a few more.. Looking at the gravitational force of all galaxies, we understood that we cannot account for a very large part of the universe. Unfortunately this is not true… We have lost 96% of the universe The missing part is called dark energy and dark matter

Nicolo Cartiglia -INFN Torino23 Movie time!

Nicolo Cartiglia -INFN Torino24 Grand Summary Particle physics studies the most fundamental aspects of nature We have done great progresses in understanding nature Many aspects are still a mystery We need young, bright motivated students, so please join us in this fantastic trip