# Search results

1. ### What do we mean when we say on shell particles?

What do we mean when we say "on shell" particles? Hello! What do we mean when we say a particle in on shell? What is off shell? I gather it is related to energy and momentum conservation to say if a process is possible, but I've no idea what it actually is. Is it something to do with...
2. ### Pion Decay to Muons and not Electrons

Hello! I'm afraid I've asked this before, a while ago, but I still don't completely understand. It's not a homework question as such, but I thought this might be an appropriate place to put it. Homework Statement Why is it that pions decay via pi^+ --> mu^+ + antimuon neutrino 98% of...
3. ### Units in Particle Physics

Hello! I was wondering if someone could help me with a problem of units! I'm currently deriving probability equations for neutrino oscillations and I'm stuck with units! I have: [(mass)^2 * time]/[4*energy] and I want to write it as [1.27 * (mass)^2 * distance]/[Energy] with distance in...
4. ### Negative Pion Decay

Hello! I was just wondering something... Why is it that a negative pion always decays into a muon and antimuon neutrino? Why not an electron and antielectron neutrino? (and the same for a positive pion) Any answers would be grately appreciated :-) Samantha
5. ### Injective and surjective?

Hello! I hope I've posted this in the correct section... I'm a 3rd year undergraduate and we're currently studying Vector Spaces (in QM) and I just don't understand what injective (one-to-one) and surjective (onto) mean? As a result I have no idea what an isomorphism is! I realise this is...
6. ### Probability of Neutrino Transformations

Homework Statement I have a questions on Neutrino Oscillations, but i have no idea how to solve any of it... this is just one part... How do I show that the probability of a mu neutrino having transformed into a tau neutrino at a time t is: sin^2(2theta)sin^2[((difference in masses...
7. ### (Kinetic Energy) Operator as a Matrix

Hey! I am completely confused... In quantum mechanics at University we are learning about operators. I don't understand what you actually have to do to write an operator as a matrix... In my notes, I'm looking at the kinetic energy operator in the Hamiltonian... I can see for something...
8. ### Neutrino Oscillations

I have a few questions about Neutrino Oscillations... Firstly, why are they called oscillations? Is it because they can go back and forth to different flavours/masses? Next, if, for example, a tau neutrino is produced in the sun, will it oscillate to the other flavours on its way to earth...
9. ### Electric Field Due to Point Charges?

Hello! Just hoping for a bit of help on a homework problem I'm doing at the moment... Basically this is the question: Three point charges are placed along the y axis: a charge q at y=a, a charge -2q at the origin and a charge q at q=-a. Such an arrangement is called an electric...
10. ### Real Physics Jobs

Hey! I'm about to start a Physics degree (MPhys) in October at Durham Uni, and afterwards I think I want to do a PhD. Just wondering what type of jobs are out there (not like being an accountant, like a real Physics job) apart from working in a university doing research and lecturing...
11. ### Electric Potential and Electric Field Strength

Hey!! I've got my A-Level Physics exam on Thursday, and I'm just doing some past papers and I'm totally confused! Please help! One of the questions (multiple choice) was saying which statement was incorrect. The answer was: Electric potential is zero whenever electric field strength is...
12. ### Stationary Waves on Strings and in Pipes?

Hey! Was just wondering if someone could shed some light on the whole stationary waves thing. I've done about them in my A-Level Physics course and I can't for the life of me figure out what it's about. I mean, why can you only have a certain number of nodes, hence certain frequencies...
13. ### How do you induce a current?

Hello! I've just realised, when trying to do a write up for a Physics experiment (about a coil and a magnet) that I don't know how you get an induced current! What's actually going on when the magnet moves through the coil? What are the electrons doing to induce a current? I'm totally...