The particle zoo

• Hadrons are fundamental particles, they are made up of particles called quarks
• Quarks, and hence all hadrons, feel the strong force and interact via its influence
• Baryons are made of three quarks (or 3 anti-quarks). Protons and neutrons are baryons.

• A meson is a particle that is made up of a pair of quarks (one is matter and one is anti-matter)
• There are no stable mesons; they all have very short half lives

(up quark and an anti-down quark)

• Kaons are mesons that are created when protons collide at high speed (created via the strong force)
• These mesons then decay beyond the nucleus so they must decay via the weak force
• This propery was coined "strange" so kaons (and the pions they decay into) are called strange particles.

• A muon is a lepton; it is fundamental like an electron and is not made of quarks so do not feel the strong force.
• A muon has more mass than an electron and has a negative charge so is sometimes called a "heavy electron".
• Muons are unstable and decay into electrons

• Kaons decay into pions (mesons), Muons and antineutrinos.
• Charged pions are less massive than kaons and decay into muon/antineutrino pairs or antimuon/neutrino pairs.
• Muons decay into electron/antineutrino pairs.

• Particle physics requires huge accelerators and immense expense.
• The reseacrh at facilities like CERN in Geneva require teams of hundreds of people to maintain the equipment and design and analyse the experiments.
• Particle physics in one area of physics where discoveries can not be attributed to an individual

"I can only speak for particle physics. But it has become obvious that on the experimental side, there has been a huge evolution in the number of people who have to collaborate because of the gigantic size of the instruments used, but also because of the enormus task that is data analysis"