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1

These branes are being smashed together so that once they are closer than the string length they become indistinguishable from a single brane. These branes have $U(N_c)$ gauge group, and in this space there is a vector. In a generic sense all Lie algebras are like the harmonic oscillator with $a$, $a^\dagger$ and $a^\dagger a$ in the structure of roots and ...


3

The question that you have asked have some vague arguments as well as some partially true facts regarding Standard Model (SM). First, Yes SM describes physics up to some energy scale which is 14 TeV. On the other hand, if we accept Plank energy ($~10^{18}$GeV) as a fundamental energy scale, then we can possibly expect new beyond the SM energy scale. A ...


1

This blog post is a good one to get a feeling of the Higgs mechanism. One should definitely separate the Higgs field from the Higgs boson. The Higgs boson is an elementary particle , attendant to the existence of the Higgs field as its excitation, and acquires its mass as all the other particles in the standard model table. The Higgs field that gives the ...


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What exactly happens to these massless degrees of freedom in the Higgs potential after symmetry breaking, i.e. after we expand the Higgs fields about the vev? You will make a redefinition of the vector fields $V_{\mu}' = V_{\mu} - \partial_{\mu} \eta $, where $\eta$ was your goldstone, Doing that you can see that a term like $$ \nu^{2} (V_{\mu} + ...


3

As you say, loop corrections change the value of the quartic coupling $\lambda$ is modified by loop corrections. If the renormalization group changed its value so $\lambda \gg 1$, the perturbative interpretation of the theory would break apart. Note that the condition $\lambda < 1$ (or $\lambda/(4\pi) < 1$) is only a hint of the perturbativity, the ...


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I just finished my freshman year as an undergraduate, but I'll tell you what I've learned. So I don't know if it's primarily due to the Higgs, but according to someone who almost has a PhD, SUSY has almost entirely been ruled out. Only "weird" SUSY theories are still acceptable. I watched a movie titled "Particle Fever" and according to the movie, the mass ...


4

I'd say that this claim is specific for the current experiments at the LHC. We collide protons there, and the protons are made of quarks and gluons -- strongly interacting stuff. You can even say that there are already $b$-quarks in the proton. So, when the protons collide, this strongly interacting stuff produce events that are similar to the genuine $h\to ...


3

In order to get a good mass accuracy using the gamma gamma channel one needs to measure well the gamma energy in the electromagnetic calorimeter which can easily contain all the energy. The four vectors have measurement errors but not missing energy. b and b_bar decay weakly to a number of particles including neutrinos and the subsequent decays end on ...


2

The masses of W-bosons and Z-bosons are known – and the mass of W-bosons multiplied by some coupling constants was known indirectly through the force they mediate, as the Fermi's constant. But the mass of e.g. the W-boson comes from the gauge-invariant kinetic term of the Higgs boson, $$ \frac 12 D_\mu H \cdot D^\mu H $$ The covariant derivative includes ...


2

The scale where some symmetry gets broken can be computed using the renormalization group equations for the gauge couplings. It's the other way around. Once you know the scales of the model (masses of the fields) you can compute the RGE. Since what ultimately matters is the mass of the representation, not its vev, if you accept some tuning (and have ...


1

@SAS answered most of the questions, however I believe there's a crucial point which still needs to be addressed: the chirality. Indeed, it is not obvious a priori why $$\Psi^T C \Psi\,\Phi\,,$$ (where $\Phi$ is some Higgs representation) leads to a Dirac-type masses instead of Majorana masses. Why not the common $\bar\Psi \Psi$? It turns out to be the ...


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The general problem that the Higgs mechanism solves is giving mass to spin-one particles. It turns out that finding relativistic, unitary theories of spin-one massive particles is non-trivial. There are a few known ways of doing it (this paper has a pretty good list of sources), but the oldest and easiest is probably the Higgs mechanism. In contrast, there ...


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Of course the SM Higgs gives mass to both fermions as well as the gauge bosons. However, the latter is much more fundamental and predictive than the former. Point is, it is enough for a scalar to transform non-trivially under a gauge symmetry to contribute to its associated gauge bosons masses (after taking vev). This contribution is constrained by the ...



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