Hi all. I've just finished watching Richard Feynman's New Zealand lectures on QED. The lecture was in the late 70s, and I'm wondering if we've learned any more since then about how Bosons 'travel'? (In that the percentage of photons that reflect of, say, a glass surface is dependent on the thickness of the glass, raising the question of how does the photon know whether to reflect or not), or are we no closer to figuring out what is going on at that level? I've only studied physics to high school standards, but do have a surface level 'knowledge' of particle physics (unfortunately my maths really lets me down).

As the title suggests, I want to know which is better career wise if I want to work in experimental particle physics ( Data analysis). Also do all US universities require GRE physics?

Hello I’m an incoming freshman at Purdue university for First Year engineering. I’ve always been interested in aerodynamics, propulsion, and particle physics. If I were to major in MechEng can I still do a PhD in physics straight away? Or should I look into transferring to better colleges? I heard Purdue is not worth for physics (should’ve committed to UIUC smh)

Hello, I am a physics student at a University in India and I am about to complete my Bachelor's in May. I guess it maybe too late now to apply for any internship or summer school that may start in June or July but I would still like to know if there are any institutes abroad that accept international students and preferably provide some stipped and/or accomodation. Thank you in advance!

If you have a pair of entangled photons and one hits an atom is absorbed and a new photon is emitted, is the entanglement broken? (Or are more particles/atoms now entangled?)

It could be positrons with the nucleus having a negative charge. How do the particle physicists explain it?

I am learning about Feynman diagrams. Is it correct that this diagram describes the "collision" aka repulsion of two electrons? And is this the collision that fx prevents my hans from going through a wall?

Hey guys!

Now I'm recreating this topic after taking the time to study more

Context: I am an Aerospace Engineering student and I am in my first year of graduation. I attended Technical College of Telecommunications in Brazil in high school. And last week my professor of fluid mechanics and wave physics called me for a crazy idea that the University raised some money for: He wants to make a linear particle accelerator.

The question: What is the best project to flow? We want something that can provide many experiences, something usable that isn't just used for one or two purposes

I'm thinking about an ion accelerator

Other questions: what is the difference between proton accelerators and ion accelerators? Because to me this is literally the same thing

Sorry for a some bad chose of words, I am new in English and especially on Redid

Hello! I am a academic of Aerospace Engineering and i am working in find a new project to my university. Can someone help me? I want build a Linear Particle Accelerator to us and I don't no any project. I want accelerate neutrons.

Sorry for my English, it is my first time write a something

Edit: I created a new topic for this

How come kaons are detected as their mass eigenstates (Ks and Kl) as opposed to their flavour eigenstates (K0 and K0bar). But for B mesons, we detect them as their flavour eigenstates (Bd and Bd(bar) ) and not their mass eigenstates (Bh and Bl)?

Can someone explain the difference in these two 'mixing' ?

Thanks!

Anyone know how the current job market looks? Or have tips on getting a resume on someone's desk? I'm ABD on a HEP PhD with CMS and looking for a job. Got unexpectedly laid off in January from a ML Engineer position and the job search has been extremely slow.

Why can't BSM particles enter at tree level and why can they only exist in loops? Afterall, whether the W boson(say) enters at tree level decay or in loops, it is an off-shell W boson regardless!

For example Tree level : B --> J/psi Ks (Off shell W boson, two weak vertices ) Loop level: B --> Ks Ks (Gluconic penguin decay with an off-shell W boson, two weak vertices+ two strong vertices) ?

https://preview.redd.it/gci8l9vse9sc1.jpg?width=1080&format=pjpg&auto=webp&s=ddf1b0a174c5140dac6021a1ff917e11bd3af6c1

I have heard that if an electron collides with another atom in an accelerator, the electron jumps to another excitement level but soon it falls back and emits a photon. Please correct me if I'm wrong. I was just wondering, how do we know which excitement level did it hop on? I don't know much about it and I'm sorry if it's a stupid question for you.

Thanks in advance

I want to know if there is a formula for calculating the angle of deviation or deflection a charged particle experiences while exiting a magnetic field

Basically the question. I want to understand how exactly the GIM mechanism suppress FCNC at tree level but allows at loop level. I understand the Z to ffbar thing, were ∆S = 1 cancels out. But I am still a bit confused on this as why FCNC this happen?

Thank you!

And/or how can I get them?

In the book "The historical development of Quantum Theory", volume 3, chapter 5, page 202 of my edition, there's a quote from Bohr I really want to understand

For context, the idea of spin had been published just a few weeks ago by Samuel and George, Bohr read it but he was unconvinced, then he found Einstein at a party and they talked about it. Then as Bohr wrote in a letter to Ralph Kronig:

"...Einstein asked the very first moment I saw him what I believed about the spinning electron. Upon my question about the cause of the necessary mutual coupling between the spin axis and the orbital motion, he explained that this coupling was an immediate consequence of the theory of relativity. This remark acted as a complete relivation [sic, revelation] to me, and I have never since faltered in my conviction that we at last were at the end of our sorrows"

Bohr to Kronig, 26 March 1926

Here's the thing, I know that if you take Schrödinger's Equation, you apply relativity to it and then you "take the square root" you get Dirac equation and then you get spin for free. I've done that derivation many times, i saw it in class, I understand that part

The problem is that back then they didn't have Dirac's equation, they didn't even have Schrödinger's, so how did Einstein see this? What reasoning led him to conclude this? I am so supremely confused

Also, I'm not entirely sure what Bohr means by "mutual coupling between the spin axis and the orbital motion". Is he talking about about the relationship between the quantum numbers for the energy level and the angular momentum? Is he talking about the fact that each combination of angular momentum and energy level has to be unique, in other words, is he talking about the exclusion principle?

This conversation was important because Einstein convinced Bohr to take the idea of spin seriously, Bohr convinced Heisenberg, and Heisenberg convinced Pauli, who then finally found his famous matrices, so this conversation is like the first domino in the chain and that's why I want to understand it

I want to know how can I test the accuracy of the Lorentz force equation (F = qE + qVB sin(ø)) using a real life experiment with a charged particle

I was looking at the decay series for radium the other day, and it eventually decays to lead through three separate emissions of alpha particles. Helium nuclei are quite stable, but carbon is even more stable (given that helium can fuse into carbon and release energy by doing so). So what keeps radium from just expelling a carbon nucleus all in one shot?

My guess is the electrostatic repulsion and weak nuclear force in a radium nucleus is only strong enough to spit out helium, and the strong force prevents it from spitting out anything larger in a single shot, but I’m not sure. Can anyone either confirm or tell me what’s actually going on?

Sorry if this is a dumb question, I'm trying to be less dumb

Forces result from symmetries in the Lagrangian, right? Well, fermions have a kind of symmetry and this symmetry creates quantum pressure, which in many ways behaves like a force keeping fermions apart

Of course the strength of this force depends on temperature, so that near absolute zero we have things like Cooper Pairs and quantum pressure seemingly disappears, but this also sounds like a force

The fine structure constant has a value of ~1/137 only in our energy range, if you go up in temperature it gets larger and the electromagnetic force becomes stronger. This seems analogous to how quantum pressure also depends on temperature. The difference is that quantum pressure can reach an alpha of 0 while electromagnetism has a floor of ~1/137

Maybe what happens is that since this symmetry is extremely simple this force is also extremely simple and we can represent it in the lagrangian with a simple negative sign, but the way I see it, that doesn't mean it's not a force

Hi, would it be possible to control how carbon bonds to itself with electro-magnetic frequencies? So as to apply it to generating carbon nanotubes and then using that principle to fabricate components at a nano-scale?

Hi, i would like someone to help me with a plasma-gas interface and refraction of an electron due to it. ref article 1 and ref article 2, these are the articles which i am referring to, i also need help with some calculations and other stuff. if anyone wants to help us please drop a comment and ill dm you. thanks