RE: Elementary fermions: the particles of matter… (Particle Physics Series – Episode 3A)
Hi Muphy! Very nice post! I have, as usual, a couple of comments :)
There is a 5th boson, very different from the others and with a crucial role: it provides mass to particles which interact with it.
This is strictly speaking incorrect, as the Higgs boson interacts with photons and gluons too, while these two are massless. The trick is that those interactions are higher-order ones (they arise via virtual loops of intermediate particles).
Because particles have magnetic moments, it is inferred that they must be spinning. Yet, in absolute, this idea is incorrect. A particle is not really a little sphere with a definite surface so it cannot really spin on itself in the Newtonian sense.
A very nice exercise you could ask to your students would be to calculate the rotation speed of the electron, if it would be spinning on itself. Knowing that its radius has to be smaller than 10-18m, one can show that the rotation speed is larger than the speed of light.
For example, the Isospin (I) is a quantum number associated with the strong force
I find this very confusing, as isospin does not act at the same level as the other examples you present, as it concerns the non elementary level. I would stress the difference.
the weak hypercharge(Y), a specific combination of the electric charge and a component of the weak isospin, relates to the interaction of the particle with the Higgs field
This is also confusing. I actually don't see what you mean. Note that we denote hypercharge simply as hypercharge (we are don't usually say 'weak' here).
Higgs Bosons interacts with mass-less particles? I didn’t know that. The data on the web is quite confusing. Would you mind suggesting a reference that explains that ? I reformulated the sentence in the article to avoid suggesting a non-interaction of the Higgs with mass-less particles.
You are 100% right, I checked it out. Isospin applies to Hadrons… I edited the text for that too.
Maybe we are not referring to the same Quantum Number here. Not mentioning the word 'weak' implies the hypercharge of the Strong force. I was talking of the weak hypercharge, a quantity that changes when interacting with the Higgs Field… What is conserved in such an interaction is a linear combination of the weak hypercharge and weak isospin, that actually is just the electric charge. You can reformulate the combination to put Yw as subject like this : Yw = 2(Q –T3).
Yet overall, you are correct, the way I wrote this paragraph does nothing else in my paper apart from bringing confusion, especially that I am a little out of my comfort zone here, and learning at the same time ;-).
I edited the paragraph to emphasis the idea that many other quantum numbers (like Hypercharge, weak isospin and weak hypercharge) combined with conservation rule are used to predict the existence or non-existence of given interactions and help deduct which force is involved. I would really appreciate if you could check if the way I reformulated the idea is correct ?
Thanks for your great comments. These make me progress in understanding the wonders of nature :-)!
The main discovery channel of the Higgs bosons was through its decay into a pair of photons. The bulk of the Higgs boson events at the LHC arises from its production in the gluon fusion channel. The interactions are not direct but are loop-induced (see here for a graph). There is no free parameters depicting those interactions of the Higgs with gluons or photons. They are fixed by all the other parameters of the theory.
More preciseyl, you can check here but the literature is pretty dense. You can also check the Physics Reports of Djouadi (here), but again, pretty intense.
There is no 'hypercharge of the strong force'. In the Standard Model, the hypercharge is an interaction as its own, like the weak interactions and the strong interactions. The Higgs field is charged under the hypercharge, as any other Standard Model particles. The hypercharge quantum numbers are thus fixed from the start and constant. They do not change.
The electroweak symmetry consists of the weak interactions and the hypercharge interactions, and it is broken down to electromagnetism. In short, the union of the weak and hypercharge symmetry groups include somehow electromagnetism, which is why you can relate the electric charge to the hypercharge and the weak isospin.
I have never written on this so that I have no clear post to advertise. Should I? :D
I understand what you mean now concerning the Higgs-massless particle interactions. Thank you for the links, indeed, they report pretty high level information, and to be honest, it kinds of fly above my head (Even if I have a PhD in physical chemistry, my uni cursus never brought me in a Particle Physics class... I am 100% self-taught in that subject).
When I was referring to the Hypercharge of the strong force, I was referring to the linear combination of the flavor numbers (charmness, topnesss etc…) + Baryon number (B+S+C+Bt+T) that is conserved during strong interactions but not during weak ones. (Ref: https://en.wikipedia.org/wiki/Hypercharge). i.e. I was considering it like a quantum number...
That confuses me a little... For me an interaction between particles implies one or more of the fundamental forces, there are only 4 known. Maybe you mean that the hypercharge is what we call the force taking the place of the EM and Weak force when these combine together at ultra high energy (above the higher energy threshold below which the electroweak symmetry breaks, corresponding to a first few instants after the Big Bang)?
Actually, that would be a good idea. In absolute, is it possible to discuss Particle Physics at this level while staying in Layman terms (so that even a high school student could appreciate fully the content). The first episode could be to define terms like what are symmetry groups, how they are manipulated to reflect reality and predict what happens and what does nor happen… It could be the step up from my own series for those that wish to dig deeper (like me ;-).
Okay for the strong hypercharge. This is actually something that is never used in the field (it is kind of obsolete, as written at the end of the wikipedia article). This is also the reason of my confusion :)
For the interactions, I am now writing a post about it, in the next part of the particle physics crash course for the meetup. By the way, can you come? The deadline is over but I can make an exception for you if you answer me by tonight.
Hey @lemouth. You must have missed my post on Discord. When I looked into the visit in detail, my enthusiasm was a little eroded by what it implied for me in terms of schedule... I thought it would be OK, but it really disrupts my other commitments.
February till May is really the big time of the year for my teaching activities. So I was disapointed when I realised I had to back out of this amazing opportunity to visit the LHC and meet other Steemstem members in such an environment. Mais clairement, pour moi, ce n'est que partie remise!
Hi @muphy! Yes indeed I missed your post. Too bad, but maybe in 2019...?
By the way, you mauy want to check my crash course on particle physics 2 course. I added a section just for you ^^ Please let me know whether it clarifies.
It did, thank you so much: It allows me to explore further. I commented on the post, to check if I really got it, and also to obviate a confusion I might still have concerning the electro-weak interaction.
For 2019, Sure, I would love to, and this time I can organize myself in order to not have a collision of commitments. How long in advance do you think you could be able to know a date?