The discussion centers on the movement and behavior of quarks within protons and neutrons, emphasizing that quarks do not have well-defined speeds or specific vibrational frequencies. Instead, their properties are described through momentum distributions, particularly parton distribution functions, which are derived from high-energy collider experiments. It is established that quarks cannot be observed as free particles and that their interactions during collisions lead to the creation and destruction of quarks, resulting in a variety of other particles. The conversation also touches on the predictive capabilities of the Standard Model and the randomness of individual particle collision outcomes.
PREREQUISITESPhysicists, students of quantum mechanics, and anyone interested in the fundamental behavior of subatomic particles and the intricacies of particle collisions.
No. They do not vibrate at all.mpolo said:Do neutrons or protons vibrate at a specific frequency.
Those are the only processes where we can study them in (sort of) isolation. Otherwise we only see hadrons.mpolo said:So most everything we know about quarks comes from high energy collisions?
Just to horn in on the conversation: This was surprising to me. I know that nuclei have vibrational structure (as well as rotational structure if they're non-spherical), so I just assumed individual hadrons, being composite particles, would have vibrational structure as well. Why exactly don't they? (This can be split off into another thread if need be.)mfb said:No. They do not vibrate at all.
Do you mean nucleons are different particles in excited states?mfb said:For nucleons, excited states are called different particles
mpolo said:Thanks for the links. They were very informative. So most everything we know about quarks comes from high energy collisions? In these collisions do quarks ever completely come out of the neutron and proton? According to what I read partons can not be observed as free particles. If so what happens to them?
An excited state of a proton gets a different name, e.g. "N(1440)". This is just a naming convention.Comeback City said:Do you mean nucleons are different particles in excited states?
mfb said:If you start learning quantum mechanics, start with easier objects, like electrons in atoms.
We have a model that is simple and works great and can describe hundreds of of measurements with incredible precision. This includes modeling the internal structure of neutrons and protons (and several other particles) to predict their masses. The same model that leads to the correct masses (and spin, lifetime, and various other properties) also leads to the correct predictions for collisions.mpolo said:How exactly do we know that we are not just simply modifying the quarks into appearing as other types of particles by virtue of high energy collisions? In other words maybe all we are doing is creating these non-fundamental particles in colliders during these high energy collisions which are really nothing more than two particles or specific geometries crushed together for a short period of time and then they simply decay back into stable fundamental particles.
Both are possible options. It is random.mpolo said:What happens when two protons collide at the highest energy do they still remain protons or do they turn into a shower of other particles?
The result is random. Often several pions are created, sometimes kaons, neutrons, protons, sometimes heavier particles. Typically lighter particles are more frequent than heavier particles, and hadrons are more frequent than anything else, but there are some exceptions. More and heavier collision products correspond to a smaller probability that the proton stays intact.mpolo said:Is there a chart that exists that shows for instance at different energy levels of electron bombardment of protons what other particles are produced at each increasing energy levels?
There are many programs, and hundreds of theorists work on calculations for specific processes. It is challenging to get accurate predictions. The tools typically need hundreds to thousands of CPU hours and a lot of experience from the user to produce anything useful - to get interesting results you cannot just play around with them on your home computer. There are some public results from those calculations, ATLAS and CMS at CERN made some of them public for example. But playing around with that will still take at least a few days to get used to the basics of the frameworks.mpolo said:Perhaps someone has written a program that simulates a particle collider using just the standard model and Quantum Mechanics.
They are created in the collisions.mpolo said:I want to understand where are all these new particles coming from?
mfb said:We can predict probabilities for every event. For many events, the observed probabilities will approximate the predictions (if the predictions are right).
mpolo said:I noticed this technique of retrofitting equations to match the results of experiments when I was going to websites of physicists that were talking about the search for the Higgs particle. Each time the Higgs was not found at the energy level that the equations were predicting it appeared to me that the professor modified the equation to predict the discovery at the next energy level.
That doesn't make sense at all.mpolo said:I noticed this technique of retrofitting equations to match the results of experiments when I was going to websites of physicists that were talking about the search for the Higgs particle. Each time the Higgs was not found at the energy level that the equations were predicting it appeared to me that the professor modified the equation to predict the discovery at the next energy level. Is this a common practice?
That is not what happened. The Higgs mass could not be predicted (not fully true, but within the scope of this thread it is), different experiments could look for different masses. Of course every experiment hoped to have the Higgs in "its" range. But that was always just a hope, not a prediction. The LHC was the first experiment that could search in the whole mass range.mpolo said:Ah, thanks for clearing that up. I was not sure if that is what I was seeing or not. Its just that a few days before he was talking that we expected to find the Higgs at this energy level and they didn't then the next thing is he is saying we can expect to see it here now at this new level.
Throw a die 1000 times. The expectation value for the number of "6" you get is 167. You might get 160, or 170, or some other values close to 167. But it is incredibly unlikely that you get 100 or 250 times a "6".mpolo said:How can something that is random when repeatedly performed turn into a pattern that is not random.
ChrisVer said:what kind of patterns did you mean in your posts?
what are the patterns you get by rolling a die? Do they somehow affect the result of a throw?
You can find hidden-variable theories (de-Broglie Bohm for example) - but EPR demonstrates you cannot measure those hidden variables. This is a mathematical proof.mpolo said:Now physicists will point to examples like the EPR experiment to prove that randomness really exists. But the debate is still raging on that issue as no one really knows how EPR non-locality really works.
Don't take analogies too far.mpolo said:If you know everything about a craps table, and everything about the dice being thrown, and everything about the air around the table, then you will be able to predict the outcome.