Questions tagged [electroweak]
Electroweak stands for the unification of the electromagnetism and the weak force. The unification energy scale is around 100~200 GeV, the mass scale of the Higgs boson. It is widely accepted to be formulated as a quantum field theory with gauge symmetries of U(1) symmetry in electromagnet forces and SU(2) flavor symmetry in weak forces.
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Is there a theoretical reason why mW/mπ ≈ 595 and mZ/mπ ≈ 675 as integers? [closed]
The W and Z boson masses in units of the neutral pion mass (PDG 2025) are:
mW / mπ = 595.43 and mZ / mπ = 675.58
Their ratio gives sin²θW = 1 − (595/675)² = 0.22299, within 0.30σ of the measured on-...
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Higgs Mechanism: Can different VEVs produce different residual gauge groups?
In the theory of the electroweak force, a classic example of the Higgs mechanism, the Lagrangian is given by
$$\mathcal{L} = \frac{1}{2g^2}F_{\mu\nu}F^{\mu\nu} + (D_\mu\phi)^\dagger D^\mu \phi+\mu^2\...
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Why is the $s$-channel so important in particle physics?
Due to the weak coupling with light particles, it’s very difficult to study Higgs boson in the $s$-channel like what we did on $Z$ boson. Nevertheless, there is a lot of interest to study the “Higgs ...
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How do we know if a $Z$ boson created via $s$-channel is real or not?
Here is a typical $s$-channel reaction. An electron and a positron collide at 91 GeV and merge into a $Z$ boson, which quickly decays into a pair of muons. However, such a reaction can occur at much ...
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Multipling a doublet by a singlet
This question is about something from page 162 of Physics from Symmetry by Schwichtenberg (second edition). The doublet is an electroweak $SU(2)$, say a left-handed neutrino and left-handed electron. ...
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Will a Higgs factory reveal something new besides testing existing theories?
After the discovery of Higgs boson at LHC, multiple lepton colliders like FCC-ee, ILC, CLIC, and muon colliders were proposed. These colliders can produce Higgs bosons under very clean backgrounds to ...
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Proving invariance of Yukawa sector under $SU(2)_L\times U(1)_Y$
As the title suggests I am trying to show this invariance. But before I do that I will explain what the crux of the problem, for me, is. This post might be a bit lengthy, but I believe it is necessary ...
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Understanding the procedure of calculating mass terms for $Z^0_\mu$ and $A_\mu$
When Peskin tries to calculate the mass terms for the gauge fields (page 701) for the following expression :
$$\Delta\mathcal L=\frac{1}{2}\frac{\nu^2}{4}(g^2(A^1_\mu)^2+g^2(A^2_\mu)^2 + (-gA^3_\mu + ...
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Visual representation of the VEV of a scalar that transforms as a spinor of $SU(2)$
Peskin starts his treatment of SSB (spontaneously symmetry breaking) by considering a non-abelian example. He considers an $SU(2)$ gauge field coupled to a scalar field $\phi$ that transforms as a ...
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What is the parity of a neutrino?
A summary of my understanding:
The electron is conventionally assigned a parity of $+1$. From Dirac theory it then follows that the positron has parity $-1$.
Parity anticommutes with momentum, so that ...
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Understanding the different $SU(2)$ symmetries [closed]
I am confused when it comes to the relation between some arbitrary gauge transformation/ internal symmetry and the different symmetries considered. I will illustrate this by considering the $SU(2)$ ...
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How do we account for unstable real particles using Feynman diagrams ($W$, $Z$ boson)?
I have recently been concerned with the production and detection of $W^{\pm}$ and $Z^0$ bosons. As it is well known, the literature is often unclear about virtual/real particles, so let me premise ...
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How was the spin of $W$ and $Z$ bosons determined empirically?
Since these are so short-lived, I'm assuming spin cannot be determined "traditionally" through a Stern-Gerlach apparatus. Are $W$ and $Z$ assumed to have integer spin because the theory ...
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Higgs decay into $ZZ$ or $WW$ [duplicate]
I was studying this graph:
(Source)
I was wondering why there is such a big difference in the branching ratio of $H \to WW$ and $H \to ZZ$. I know that for the Higgs mass of $125\,\text{GeV}$ both ...
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Feynman parametrization goes wrong
I am trying to reproduce the results found in R. Jackiw, S. Weinberg, Phys. Rev. D 5 (1972). The following loop integral is the only one that is giving the wrong result:
$$
\require{cancel}
\...
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