A –Level Physics: Nuclear Physics Quarks

Objectives:

FLASHBACK FLASHBACK: Explain how you could determine the speed of sound using a microphone and oscilloscope set-up (6 marks)

Starter Activity Answer the following: Initially the muon was incorrectly identified as a meson. Explain why a muon is not a meson A sodium atom contains 11 electrons, 11 protons and 12 neutrons. Determine the correct number of hadrons, baryons, mesons and leptons in sodium A muon is a lepton and as such is a fundamental particle (not made of anything smaller). Mesons are made up of smaller particles. 2) 23 hadrons, 23 baryons, 0 mesons, 11 leptons

Independent Study Watch: https://www.youtube.com/watch?v=CBrsWPCp_rs Then: Write a page outlining new information that you have gathered about quarks, particles and time

Quarks On a spare A4 page draw the following six quarks with space in between to add information as we go along.

What do you think antiparticles of hadrons are made from? Building blocks Just like leptons, quarks are fundamental particles and as such are the building blocks of hadrons. There are three main quarks that you’ll deal with… -400BC antiquarks The first two, up and down quarks are the only two you need to make protons and neutrons (hadrons). The strange quark gives particles a bit of extra ‘strangeness’. NB: this is an actual property! What do you think antiparticles of hadrons are made from?

Properties of Quarks Firstly, stick your provided tables into your book (away from your A4 page). Then use them to add information to your quark diagram page Each quark has an antiquark that is the antithesis in almost all respects. To indicate an antiquark, the quark symbol is headed with a small dash (-) Proton= up up down and Neutron= down down up The quarks can be combined to make the particles you have previously learned about. Charge and Baryon number must be conserved Knowing that a proton (+1 charge) and a neutron (0 charge) have a baryon number of 1 (being a single baryon after all)…Determine their quark recipe

A little bit of history In the 1960s, evidence was gained (via ‘electron microscopic photography’) for the existence of up, down and strange quarks -400BC Two more quarks were detected in the following decade, called the bottom and charm quarks. As you can gather, the symmetry of the model shows that the quarks come in pairs, up with down, charm with strange and this symmetry/pair pattern lead to the prediction that the bottom would have a partner, coined ‘top’. This wasn’t actually found until the mid 90s. These three quarks (bottom, top, charm) are unstable so aren’t dealt with much in this unit! 5.1 x 10-10 N

Baryons covered…but how about mesons? So as you’ve found out, baryons are made up of three quarks (or three antiquarks if antiparticles) but mesons are actually made of just one quark and one antiquark -400BC The diagram shown to the left is the conventional way of showing the structure of a particle. This particular one shows a positive pion Draw the structures for the following mesons using the data below. Draw them on your A4 page 5.1 x 10-10 N Negative Pion = anti-up and down Neutral Pion= up and anti-up OR down and anti-down Positive Kaon= up and anti-strange Neutral Kaon= down and anti-strange Negative Kaon= strange and anti-down

Call my Bluff- Particle Interactions You’ve seen a few particle interactions before such as with Beta+ decay. In Beta- decay, a neutron decays into a proton. To balance out this newly made positive charge, an electron is also produced (along with its antineutrino) as shown: -400BC neutron proton electron electron antineutrino This is an example of this in action! Notice the element has changed as the proton number has changed! 5.1 x 10-10 N If you like, you can also show the same equation but in terms of quarks rather than the particles themselves! Have a go! Down up electron electron antineutrino

Feynman Diagrams You might be unlucky in an exam and be given the equation as a Feynman Diagram. These can be in various orientations but basically shows the interaction process (in this case, the neutron bottom left) changing into a proton and producing an electron and electron antineutrino (via a W-boson intermediate)

Call my Bluff- Particle Interactions You may be asked in the exam whether interactions are possible or not. You will easily be able to determine this as long as you follow the rules below: -400BC Energy and Momentum must be conserved Charge must be conserved Baryon Number must be conserved (total number of baryons before is same as after) Lepton Numbers must be SEPARATELY conserved. If you are analysing an interaction and the interaction disobeys ANY of the laws, it can be rejected straight away 5.1 x 10-10 N

Exam Question Complete the exam practice provided. Use all your notes to help. I will assist you through the questions only once all are attempted and when you have marked your answers according to the mark scheme. NOTES: show all your workings and pattern of thought, do not be vague 5.1 x 10-10 N