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Questions tagged [standard-model]

A model of the basic particles and forces featuring six quarks, three charged leptons, three massless neutral leptons and four fundamental force carrying bosons. The twelve fermions are arranged into three generations, while the bosons serve to explain the electromagnetic interaction plus the strong and weak nuclear forces (and the Higgs mechanism). Do NOT use this tag for the standard model of cosmology, etc..

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Experimental evidence of interaction out of thermal euilibrium?

Sakharov gave three conditions for the matter-antimatter asymmetry observed in the universe. (1) Baryon number violation: Don’t have any experimental confirmation yet. (2) C-symmetry and CP-symmetry ...
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What do we mean with spontaneous symmetry breaking $SU(2) \times U(1) \to U(1)$ in particle physics?

I think my problem is with group theory. I understand that within the Standard Model the Lagrangian is invariant under $SU(2)_{L}\times U(1)_{Y}$ symmetry, but I do not understand what we mean (...
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F-type and D-Type Coupling between meson baryons

What is the basic definition and detailed meaning of the D-type (symmetric) and F-Type (symmetric) coupling between mesons and baryons. Why the name D and F. What is their origin?
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Isospin and $\Delta$ Production

Edited to add new information I have seen the relation between cross sections postulated: \begin{align} \sigma(\nu+p\to\mu^- + \Delta^{++})=9\sigma(\nu+n\to\mu^- + \Delta^{+}) \end{align} Motivated ...
59 views

Mixing matrix in particle physics

It is familiar for us that the diagonalization of a mixing matrix which is written in the neutral basis gives the masses of the neutral particles. If I construct a mixing matrix which is written in ...
109 views

What if there were only 1 generation of fermions?

The number of fermion generations has many effects beyond the mere existence of "3 copies of fermions," including determining scatterings, constraining CP violation, influencing electroweak symmetry ...
83 views

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What determines the Lifetime of $Z$-Boson?

What determines the lifetime of the Z Boson? Is it it's mass? What else is involved? Is the coupling to Higgs involved?
88 views

Higgs critical temperature?

Higgs mechanism is defined to operate (give spontaneous symmetry breaking) below some critical temperature. As mentioned, for ex. in Wikipedia: Below some extremely high temperature, the field ...
50 views

Heirarchy problem

Can anyone explain the hierarchy problem in context to Higgs mass corrections by scalar loop and fermion loop (the problem arising when we try to treat SM as an EFT)? and how do these corrections ...
81 views

Do Quarks decay into Photons at high enough temperatures?

At high enough energy, particles lose coherence and are ripped apart into a Quark-gluon plasma where the individual quarks can break free of the atomic nucleus and fly around unencumbered. A black ...
180 views

How does the Higgs field prevent the electron from going the speed of light?

Both the Photon and the Electron are point-like particles. Most massive particles can be thought of "bound collections of massless particles", but the electron assumed to be a "point particle with a ...
49 views

Possible Feynman diagram for $\tau^+ \rightarrow p \mu^+ \mu^-$ and $\tau^+ \rightarrow \bar{p} \mu^+ \mu^+$?

I want to know the possible Feynman diagram for these two lepton family, lepton and baryon number violating tau decays. These decays are forbidden in the Standard Model. But the further extension of ...
77 views

Are there compelling reasons not to organize the elementary particles by charge and spin? [closed]

I don't like the way the standard model is currently displayed (see second picture for reference). It does a poor job of abstracting the information into something understandable. As far as I ...
46 views

What does matter look like in the absence of photons?

Another question inspired by this one on alternative standard models. Greg Egan's story Wang's Carpets (or the similar segment of the larger novel Diaspora) sketchily describes a universe with no ...
65 views

Chemistry without electrons?

This question on the behavior of a universe with massless electrons got me wondering: what would atoms look like if electrons were not merely massless, but rather the lepton fields just didn't exist ...
121 views

Do elementary particles have a density?

The SM supposes elementary particles are structureless unless composite objects like hadrons. For bosons, that can occupy the same state, we can define energy or mass density. The same happens but ...