High Energy Particle Physics Chapter 17 Summary

Outcomes You will explain how the analysis of particle tracks contributed to the discovery and identification of the characteristics of subatomic particles You will explain, qualitatively, in terms of the strong nuclear force, why high-energy particle accelerators are required to study subatomic particles You will describe the modern model of the proton and neutron as being composed of quarks You will compare and contrast the up quark, the down quark, the electron and the electron neutrino, and their antiparticles, in terms of charge and energy (mass- energy)

Particle Accelerators Particle accelerators are massive machines which are used to produce new particles by accelerating and colliding charged particles at very high speeds The new particles are often very unstable and decay quickly

Particle Accelerator - Parts All particle accelerators must have the following: a source of charged particles a means of accelerating the charged particles (ex. electric field) a tube or container in which the charged particles are collided In order to form new particles (breaking apart current particles), charged particles must have a great deal of energy to counteract the strong nuclear forces in the nucleus This energy is in the form of kinetic energy…therefore, charged particles must be accelerated to incredible speeds as they have very small masses (think: Ek = ½ mv2)

Particle Accelerator – Large Hadron Collider (LHC)

Particle Detectors The new particles formed following a collision are too small to see, therefore scientists must have other means to detect these newly created particles Bubble Chambers and Cloud Chambers: As the particles travel through the chambers they will leave tracks From these tracks we can learn: the charge-to-mass ratio of a particle (q/m), as well as the type of charge (+/-), both of which dictate the deflection of the particle

Particle Detectors

SAMPLE PROBLEM The diagram below shows the tracks left by three particles that have passed through a region where the magnetic field is uniform and is directed into the page. Each particle traveled in the plane of the page, initially. Now assume the particles had identical masses and speeds, and they differed in their charges. Which particle represents the following: alpha particle, proton, anti-up quark?

How the Large Hadron Collider works… https://www.youtube.com/watch?v=dw3KuNgD-jE https://www.youtube.com/watch?v=AwNwCs2CH7w

Some extras…..

The Standard Model During the 1950s, more and more elementary particles were discovered, mainly due to particle collision research using particle accelerators In 1962, Murray GeIl-Mann suggested that the elementary particles were made up of smaller particles (quarks), this was the beginning of the Standard Model of Elementary Particles

The Standard Model This model describes the elementary particles and the interactions (forces) between them

Need to know: First generation quarks (up and down) and leptons (electron and electron-neutrino) Fundamental forces

Pair Production vs. Annihilation Pair production: sometimes, a photon turns into a particle and its antiparticle, for example, an electron and a positron Annihilation: when a particle meets its antiparticle, the two annihilate each other to form 2 photons (due to conservation of momentum) with sum total energy equivalent to the total mass-energy of both particles

Homework p. 851 #5, 9, 13, 16, 19