# Tag Info

2

A higgs boson is created at an accelerator just like any other particle, by converting energy to mass, according to the famous equation $$E = mc^2$$ If you take the LHC as example, then protons are accelerated to nearly light speed, having enough energy to create particles as heavy as the higgs. For a particle to decay it needs phase-space (i.e. the ...

5

No. You have just named a series of unanswered questions as if the fact they're unanswered somehow invalidates the Standard Model. This is not in general how science works. For the extensive evidence for the Standard Model, please see http://arxiv.org/abs/hep-ph/9810316 among many other things.

0

The first assumption is that whatever vev the higgs picks up is constant in space, because this has less energy than one that increases the kinetic term in the Lagrangian. So we can do one global transformation to make the vev be in the second component only. You can imagine doing this prior to symmetry breaking, if you know what it is going to be ahead of ...

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Well, after symmetry breaking, all that remains is electromagnetic $U(1)$, so the only generator that is truly a symmetry generator is $Q$. The fermions couple to the "Higgs" via the Yukawa coupling: $\mathcal{L}_y = -y_e^{ij} \bar L_{L,i} \Phi e_{R,j} - y_u^{ij} \bar Q_{L,i} \tilde{\Phi} u_{R,j} - y_d^{ij} \bar Q_{L,i} \Phi d_{R,j} + h.c.\,$ which mixes ...

3

Now that we have seen the Higgs boson, all the particles predicted by the Standard Model have been discovered. The penultimate particle to be discovered was the tau-neutrino at Fermi-Lab in 2000. The antepenultimate particle to be discovered was the top quark, also at Fermi-Lab in 1995. For a complete timeline, see e.g. this wiki page. There are, of ...

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I agree with the answer of Quantum physicist , that zero mass for neutrinos was an input to the standard model , not a prediction, because measurements showed a mass compatible with zero. But I will add that the discovery that neutrinos must have mass does not destroy the Standard Model, just different Lagrangian for the neutrinos has to be included. ...

6

I think that this question can be answered in three parts: Are there any exact solutions to any equations of the SM? Do we always have to use perturbation methods to solve anything within the SM? Are there any exact solutions beyond the SM? The answer to question 1 is: it depends on what equations you are referring to. For example, the propagators of ...

3

Standard model doesn't predict that neutrinos are massless. It's a "Model", where initially neutrinos are considered massless, because no mass was observed. The way we know, now, that neutrinos have masses, is through the mixing between the different neutrino types, through a matrix called the PMNS matrix (similar to the CKM matrix for quarks). This mixing ...

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Exact solutions, hmm... not so sure. Exact results, yes. Because of symmetry, there are a large number of things that are known to be zero exactly, and I believe in some cases we know the form that corrections take (they are "protected" by things like gauge invariance and chiral symmetry)

-1

Until recently, quark masses were thought to be one-third of a protons' (612 "electrons"). Now, experimentalists state "bare quark mass" to be about one percent of this at any given moment (based upon their observations). But a difference exists between how positive and negative charges carry mass because the more massive quarks (e.g. "top") are positive ...

3

Neutrino mass is not in conflict with electroweak theory. One can introduce neutrino masses by modifying the Higgs or lepton sector of the Standard Model. The simplest method, that which you propose, is introducing a right handed neutrino with a Yukawa coupling with the left handed neutrino (extending the lepton sector). The right handed neutrino, however, ...

3

Tarek (OP) e-mailed me to contribute to this thread. Here's the response that I gave him (slightly edited for clarity). I see why this was confusing, my apologies! I was perhaps too glib in the post. Iwas implicitly talking about a chiral rotation but wanted to present it somewhat more intuitively. Let me try to spell it out more carefully, and hopefully ...

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