# Tag Info

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QED is the theory of electrons and photons only. When extended to the Standard Model quark loops are included.

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Higgs Yukawa coupling does preserve chiral symmetry. What is missing in some text books is that under axial rotation $$\psi_L\rightarrow e^{-i\theta},\psi_R\rightarrow e^{i\theta}$$ the Higgs field transforms as $$H\rightarrow e^{-2i\theta},$$ hence the Yukawa coupling $$\lambda \bar L H e_r + h.c.$$ is invariant under axial rotation. Upon ...

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The baryon content of the universe is made of protons and neutrons, nearly all of which exist as hydrogen and helium nuclei. In contrast, the lepton content of the universe has significant contributions from electrons in atoms and neutral plasmas neutrinos produced in stellar cores anti-neutrinos produced in decays of neutron- rich nuclei the cosmic ...

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The plus-or-minus figure that you list ($\pm0.0021\,\mathrm{GeV}$) is the error on the mean and not the width of the distribution which is very wide. The usual source for looking up such basic particle data is the Review of Particle Physics published and maintained by the Particle Data Group. The Review is availble for download and on-line browsing on the ...

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The polarized vacuum is effectively described by the Euler-Heisenberg lagrangian. The nonlinear term is proportional to the inverse of the virtual particle mass, so lighter particles like electrons contribute the most.

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The standard model of particle physics, which has the quarks and leptons in group structures of $SU(3) \times SU(2) \times U(1)$ was developed BECAUSE most of the data of particle physics can be fitted with this model, and because it is successful in predicting new data. That is why you can write a number of possible quark states and quark antiquark states, ...

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