A –Level Physics: Nuclear Physics Particle Classification

Objectives:

FLASHBACK FLASHBACK: Calculate how high and how far a ball will go if hit with a resultant velocity of 12ms-1 at 40 degrees from the horizontal

Starter Activity Use pages 96 and 97 to answer the following: How is the timing of the acceleration in a cyclotron maintained? Use formulae to prove that the frequency of the cyclotron dees is independent of the radius Include the relativistic effects of mass in the formula What is a synchrotron? Explain a situation whereby scientists were caught out for cheating 5.1 x 10-10 N

Independent Study Make notes on the large hadron collider using the handouts provided. Answer all questions on page 103

Creation E= mc2 Worked example One of Einstein’s most important theories was the theory of creativity and this equation states that energy and matter are regularly interchanged. -400BC E= mc2 This equation shows that multiplying the mass (m) of an object by the speed of light (c) squared gives you the equivalent energy (E) Sometimes (such as in a gamma ray photon) particles can spontaneously appear from pure energy. Worked example A gamma ray-photon converts into an electron and a positron (identical mass but opposite charge). Calculate the frequency of the gamma photon. (Nb: mass of electron= 9.11x1031kg and plank’s constant = 6.63x10-34) HINT: First step, use the equation above. Second step, use E=hf. 5.1 x 10-10 N

Creation E= mc2 E= mc2 so using this you get E=(3x108)2 x 9.11x10-31 Sometimes (such as in a gamma ray photon) particles can spontaneously appear from pure energy. Worked example A gamma ray-photon converts into an electron and a positron (identical mass but opposite charge). Calculate the frequency of the gamma photon. (Nb: mass of electron= 9.11x10-31kg and plank’s constant = 6.63x10-34) E= mc2 so using this you get E=(3x108)2 x 9.11x10-31 = 8.2x10-14J but you multiply by 2 as you’re creating 2! =16.4 x 10-14J E=hf so f=E/h which gives f as 2.47x1020Hz -400BC 5.1 x 10-10 N

SO now consider momentum Creation E= mc2 Sometimes (such as in a gamma ray photon) particles can spontaneously appear from pure energy. SO now consider momentum -400BC What can we tell from this situation? Consider the direction of the particles being created The process can be likened to an explosion. But instead of the before situation having mass as below, it’d have the equivalent energy! Use the law of conservation of momentum to explain how this shows momentum is conserved 5.1 x 10-10 N

Annhilation Flashback! Explain with reference to annihilation how gamma rays are produced and how this obeys the law of conservation of momentum Just as matter can spontaneously form from energy, energy can form from the disappearance of mass The sum of the mass before is always more than after as some mass is converted into energy. If a particle and an antiparticle collide, their mass will disappear and be converted into equivalent energy

Delving Deeper In terms of normal matter, all of you will be familiar with protons and neutrons once considered to be the smallest unit of matter. However, we now know this is not the case as these particles consist of even smaller particles called quarks. Even more exciting is the finding that there are particles not found in normal matter, and these particles can only be found in cosmic rays and particle accelerators. You will need to know all their properties such as their charge, classification and relative mass! So we will now start…

First classification: Hadrons vs Leptons There are various ways that we can classify particles, and it can seem a little confusing, but we will gradually build up a ‘particle map’ that will allow you to identify any mystery particle you are given. Think of it as using a family tree to find an individual! First classification: Hadrons vs Leptons Vs HADRONS are made up of smaller particles so are NOT fundamental particles LEPTONS are fundamental particles and are not made up of anything smaller

Second classification: Baryons Vs Mesons In this route we are following the hadron division. There are two types of hadrons, baryons (and anti-baryons) and mesons. You classify them by the number of quarks that they consist of (more on this later) Protons and Neutrons are the most well-known of the Baryons. Now you should start to consider them two versions of the same particle, the nucleon. There are however baryons you do not get in normal matter such as sigmas (Σ)

What does annihilate mean in physics? More about Baryons Protons are the only stable baryon. Think of them as the default state as every other baryon will eventually decay into a proton. Antiprotons and Antineutrons (antibaryons) are the antiparticle of protons and neutrons. When they meet their corresponding particle, they annihilate each other. What does annihilate mean in physics?

Baryon number Just like the mass (nucleon) number, the baryon number is the number of baryons in an atom. The difference between the nucleon and baryon number is that the baryon number includes ALL baryons, such as the sigmas. Each particle (including particles that are not baryons) have a corresponding baryon number. NOTE: THE TOTAL BARYON NUMBER IN ANY PARTICLE INTERACTION MUST BE CONSERVED (never change) How does this help us determine whether a specific interaction will happen or not? PARTICLE NAME BARYON NUMBER Proton and Neutrons +1 Antiprotons and Antineutrons -1 Others (sigmas and non-baryons)

Now the other hadron…mesons One of the ‘others’ in the previous baryon number table is the meson. It’s not a baryon and so has a baryon number of zero. They are all unstable so will always decay. Pions (π-mesons) are the first type of mesons. They are the lightest and have three different charge types, π+ π- π0 The heavier type of meson is the kaon. They are the most unstable. Both types of meson were discovered in cosmic ray showers. You get lots of pions also in high energy collision like at CERN

Second Classification: Leptons Leptons are known as fundamental particles as they are not made up of anything smaller. There are three types; electrons, muons and tau. The latter two are like heavy electrons ν is the greek symbol ‘nu’ Electrons are stable but muons and tau are unstable, eventually decaying into the default state of an electron They all come with a corresponding neutrino that has almost zero mass or charge. They can pass through the earth without doing absolutely anything!

How would a photon be classified? Classifying Leptons Just like the baryon number is the number of baryons, the lepton number is the number of leptons that an atom has. There is however a slight difference, which is that there are three different lepton numbers that must be counted separately It has no charge no baryon number no lepton number it only has energy How would a photon be classified?

TASKS In pairs, create a detailed and neat flowchart that would allow you to identify a mystery particle. Each checkpoint should have a question followed by yes/no options. E.g. The first question could be “is it a fundamental particle?” -400BC Once complete, play a quick game whereby you think of a particular mystery particles and your partner can only ask yes or no questions. Whoever needs to ask the least questions to identify the particle wins! Alternating the polarity of the tubes, so that the particle is accelerated toward one and repelled from the other. The particle needs to spend the same time in each tube and as it’s speeding up, it needs to be able to travel a greater distance Answer the following: What is the difference between a hadron and a lepton 2) If a collision at CERN produces 2 protons, 3 pions and 1 neutron, what is the total baryon number? 3) Which two particles have a lepton number of L(mu)+1

Exam Question 5.1 x 10-10 N