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 ...

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35 views

W boson one loop electroweak contribution to muon g-2

I want to calculate the one loop W boson contribution (triple gauge boson vertex WW-Photon) to the muon anomalous magnetic moment g-2 with the help of Dimensional Regularization. Diagram given below: ...
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61 views

Understanding $ee\to h \to ff$ process

can anyone tell me where to find a good reference that talks about $$e^+ e^-\rightarrow H \rightarrow f\bar{f}$$ where this describes an electron-positron annihilation into a Higgs that in term ...
2
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1answer
27 views

Electroweak precision in the future

LEP has measured electroweak precision observables to an extremely good precision ($\sim 0.1\%$). The future linear collider is expected to run far from the W and Z poles so other then higgs and top ...
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34 views

$ZZ^{(*)}$ decaying to leptons mass spectrum

I was looking the mass spectrum of the $ZZ^{(*)}$: and I was wondering why the shape is the way it is. The peak around 90 GeV is the single Z resonant, what is reason behind the slight peak in the ...
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21 views

Why third Pauli $\tau_3$ becomes third Isospin component $\tau_3^{<\Phi>}$?

When considering the higgs coupling to the neutral gauge boson of EW theory (see e.g. C. G. Tully (EPP nutshell) page 102): $$\tag{1}\mathcal{L} = \frac{1}{4}\left\{\left(g' B_\mu Y_\Phi+gW_\mu^3 ...
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1answer
17 views

phase transition and effect on leptogenesis

What is the effect on leptogenesis in the standard model if the electroweak phase transition is (i) first order and (ii) second order?
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53 views

How to theoretically determine electric charges of $W^{\pm}$ bosons?

I just realised that I don't remember how to conclude theoretically that $W^{\pm}$ bosons have electric charges of $\pm 1$. After some searching I'm quite surprise that I couldn't find a satisfying ...
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2answers
218 views

Are all fermions massless at high temperatures?

According to the standard model, the electroweak symmetry is unbroken at high temperatures, and therefore all gauge bosons are massless then. But since fermions are said to acquire mass by a different ...
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4answers
160 views

temperature of electroweak phase transition

How does one estimate the temperature at which electroweak phase transition (EWPT) occurred? Somewhere I have read it is around 100GeV but the reason was not explained.
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1answer
60 views

Is the weak interaction Lagrangian invariant under parity transformations?

The weak interaction term in the Lagrangian reads $$ \bar \Psi \gamma_\mu P_L \Psi W^\mu. $$ Under parity transformations, because of $\Psi \rightarrow \gamma_0 \Psi$ and $\gamma_5 \rightarrow ...
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47 views

If weak isospin is not conserved in time, what does the Noether theorem tell us?

As far as I understand weak isospin is only conserved in interactions but not as time evolves. Nevertheless, we get from Noethers theorem, because of global $SU(2)$ invariance a conserved quantity ...
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341 views

Are there really left-chiral particles?

A chiral eigenstate is always a linear combination of a particle and an antiparticle state and a particle or antiparticle state is always a linear combination of chiral eigenstates. Now, how can we ...
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40 views

Mass generation for Z' and W' bosons

I read that some Beyond the Standard Model theories require the existence of additional gauge bosons such as $Z'$ and $W'$. As far as I understood, an extension of the $SU(2)_L$ symmetry is required, ...
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2answers
76 views

Unification of the electroweak theory

Can the electroweak theory be described by the spontaneous symmetry breaking of $SU(3)$ to $SU(2)\times U(1)$?
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1answer
33 views

What theory unifies the electroweak and the strong forces? [closed]

As the title itself suggests, here's my question: What theory unifies the electroweak and the strong forces?
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1answer
108 views

Why doesn't the photon have mass? The Higgs mechanism and pre-electroweak epoch

1) When electroweak separation occurred, 'why' wasn't the photon 'given' mass like the W and Z bosons? i.e why don't photos interact with the higg's field? 2a) How well is the higg's mechanism ...
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2answers
47 views

Lepto-genesis and electroweak theory

Is there any term in standard electroweak theory that breaks CP-symmetry and thus explains lepto-genesis?
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1answer
65 views

Glashow-Weinberg-Salam mass terms

At the end of spontaneous symmetry breaking I get these mass terms: $$W_{\mu}^{\pm}=\frac{1}{\sqrt{2}}\bigl(W_{\mu}^{1} \mp i W_{\mu}^{2} \bigr )$$ $$\mathcal{L}_{mass}=\frac{1}{2} g^2 \frac{v^2}{4} ...
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1answer
136 views

Higgs Mechanism

In Higgs mechanism, we take the combination of LH $SU(2)$ doublet and RH singlet along with Higgs doublet so that the overall weak hypercharge and weak isospin is zero to be $SU(2) \times U(1)$ ...
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1answer
113 views

Invariance under charge conjugation… Or not?

I have read some paper which says that the electroweak Lagrangian includes these terms like $\bar{\psi} \gamma_a\gamma_5\psi$ and $\bar{\psi} \gamma_a \psi$. They violate charge conjugation symmetry. ...
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34 views

About Paschos-Wolfenstein relation (Weinberg angle measuring)

There is Paschos-Wolfenstein relation: $$ \tag 1 \frac{\sigma^{NC}_{\nu_{\mu}} - \sigma^{NC}_{\bar{\nu}_{\mu}}}{\sigma^{CC}_{\nu_{\mu}} - \sigma^{CC}_{\bar{\nu}_{\mu}}} = \frac{1}{2} - ...
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1answer
77 views

Weak interaction violate charge conjugate

How can we show that the weak interaction violates the charge conjugation symmetry?
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1answer
102 views

Electroweak interaction: From $W^{1}_{\mu},W^{2}_{\mu},W^{3}_{\mu},B_{\mu}$ to $W^{\pm},Z_{\mu},A_{\mu}$

EDIT: Additional question at the end I am trying to illuminate how the "unphysical" gauge bosons $W^{1}_{\mu},W^{2}_{\mu},W^{3}_{\mu},B_{\mu}$ will be the "physical" $W^{\pm},Z_{\mu},A_{\mu}$ when ...
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52 views

Without Electroweak symmetry breaking [closed]

How would the present universe be different from one if there was no electroweak symmetry breaking?
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2answers
72 views

Isotropic neutrino-lepton scattering

I'm a physics student and I'm attending an introductory course of particle physics. My professor stated that, in center of mass frame, the $\nu_\mu e^- \to \nu_\mu e^-$ elastic scattering has an ...
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3answers
151 views

Why didn't electroweak symmetry breaking happen earlier than it did?

I've read that electroweak symmetry breaking occurred "at a picosecond or so" after the Big Bang (in a source I found). I can't help wondering why it took so long to get started. For instance, was ...
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1answer
86 views

Semileptonic decays of the $B_c$ meson

I am struggling with calculating the exclusive semileptonic $B_c^+\rightarrow J/\psi l^+\nu_l$ decay. I learnt that the amplitude is given by a product of the leptonic current $L^{\mu}$ and the ...
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2answers
910 views

Is there a “difference” between photons that act as virtual particles and photons that act as the quanta of EM radiation?

I) I know that virtual-photons are known to be the force-carriers for the Electromagnetic force, and that they are called "virtual" because the Energy-Time-inequality version of the Heisenberg ...
6
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1answer
174 views

Derivation of neutrino oscillation phase factor

As we know, the neutrino $\nu_{\alpha}$ with flavor $\alpha=e,\mu,\tau$ is a linear combination of mass eigenstates: $$ |\nu_{\alpha}\rangle=\sum_iU_{\alpha i}|\nu_i\rangle,\quad i=1,2,3 $$ where the ...
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2answers
143 views

Coupling constant in electroweak theory

Electroweak theory has two coupling constants before and after Spontaneous Symmetry Breaking (SSB) each one for $SU(2)_L$ and $U(1)_Y$, though they are connected by Weinberg angle after SSB. My ...
3
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1answer
199 views

What is the parity of a $W^{-}$ boson?

What is the parity eigenvalue of the $W^{\pm}$ boson, or is it even an eigenstate? I have not found any source that discusses this. I have seen some lists of particles with their parity eigenvalues, ...
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1answer
36 views

Behavior of Pion-Mediated Nuclear Force before Electroweak Symmetry Breaking?

When Chiral Symmetry was exact, as it was before EWSB due to the lack of mass terms for quarks, would the residual strong force have infinite range? Related to this, does the Negative Beta Function ...
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21 views

Force Carrier in Fermion Generations?

Assuming that before Electroweak Symmetry Breaking all particles of a generation were identical, is it possible that they could be related to some kind of symmetry that is unbroken at higher energies, ...
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2answers
192 views

No monopoles in the Weinberg-Salam model

I'm reading Chapter 10.4 on the 't Hooft-Polyakov monopoles in Ryder's Quantum Field Theory. On page 412 he explains why magnetic monopoles cannot appear in the Weinberg-Salam model. I'm I right by ...
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1answer
199 views

Phase factors under rotations of strong and weak isospin

The strong isospin raising operator changes a $d$ quark into a $u$: $$ \tau_+ \big|d\big> = \big|u\big> $$ However, for antiquarks, there is an additional phase factor: $$ \tau_+ \big|\bar ...
7
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1answer
86 views

Very short decay: A bare quark?

I keep reading the same phrase about the very short life time of the top quark: Because the t-quark decays on a shorter than the characteristic QCD interaction-time it cannot hadronize. ...
13
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3answers
1k views

Why is the Symmetry Group for the Electroweak force $SU(2) \times U(1)$ and not $U(2)$?

Let me first say that I'm a layman who's trying to understand group theory and gauge theory, so excuse me if my question doesn't make sense. Before symmetry breaking, the Electroweak force has 4 ...
4
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3answers
263 views

Majorana Mass For Neutrinos In Standard Model

Neutrinos can't be given Dirac masses because there is no $SU(2)_L$ singlet right handed neutrinos in the standard model. But can neutrinos be given Majorana masses in the standard model? EDIT: Why ...
2
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1answer
125 views

Noether Charge Operators In Electroweak Theory

In electroweak theory, for the first generation of leptons, in the doublet $$\psi_L=\begin{pmatrix} \nu_{eL}\\ e_L \end{pmatrix}$$ we assign a non-abelian charge $I=\frac{1}{2}$. Is this a Noether ...
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80 views

Isospin and weak Isospin

What is the difference between isospin and weak Isospin? What is the difference between hypercharge and weak hypercharge?
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136 views

Are there analogs to resistance, inductance, capacitance, and memristance connecting the weak force to electromagnetism?

A question was asked over at EE.SE recently which I tried to answer, but much of my answer was speculative. I'm hoping someone here can help my ignorance. In electronics design, there are four ...
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1answer
199 views

Why are the Z boson and photon different?

If I understand right the Z boson and photon are both a mix of the same two bosons, the W_3 and the B boson of weak isospin. If the Z boson and photon are both made of the same bosons, then they ...
0
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0answers
128 views

Off-shell corrections to massive vector boson propagator in polarization form

As an exercise for myself, I have been working on rewriting the massive vector boson propagator (unitary gauge). I have run into a problem interpreting some of the terms that stick around when the ...
4
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1answer
243 views

CP violation from the Electroweak SU(2)$_{weak,flavor}$ by $\int \theta F \wedge F $

Question: Why there is NO Charge-Parity (CP) violation from a potential Theta term in the electroweak SU(2)$_{weak,flavor}$ sector by $\theta_{electroweak} \int F \wedge F$? (ps. an explicit ...
3
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1answer
256 views

Is Higgs mechanism necessary in QCD?

As we known, we introduce Higgs mechanism into Standard model to explain mass of Gauge boson, lepton and neutrino(maybe?). Higgs mechanism is necessary for electroweak theory because gauge symmetry ...
12
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2answers
390 views

How do we know we've unified two interactions?

What is the precise definition of unification of fields (in classical and quantum mechanics)? In general, does unification of a field mean that we can write both of them at both sides of an equation ...
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92 views

What's the most precise test of electroweak unification in the standard model?

As I understood, there is a coincidence of the weak coupling constant $g$ calculated in two different ways: 1) The muon lifetime $\tau_{\mu}$ is related to $g$ by the formula $(m_{\mu} c^2)^5 ...
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2answers
188 views

Conservation of Energy and CP violation

In classical mechanics there is Noether's theorem: If a system has a certain symmetry there is a related conserved quantity. Energy conservation is a result of a system being time invariant. This is ...
2
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1answer
216 views

Is the Higgs mechanism needed for Quantum Field Theory?

The NY Times article on Firewalls today has the following paragraph: Quantum field theory is how the world works [quoting a physicist]. It had a major triumph just a year ago, when the Higgs ...
2
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1answer
419 views

What led to the electroweak and strong forces splitting?

Is the reason for the split believed to be spontaneous symmetry breaking? If so, did SSB occur because the Universe was cooling rapidly from extremely high temperatures?