All Questions
Tagged with quantum-field-theory particle-physics
1,059
questions
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What are the differences of Scalar and Pseudoscalar Yukawa Theory?
I know that some polarized interactions are forbidden.
But for unpolarized (summed over incoming and outgoing spins), are the amplitudes and decay rates of a Yukawa scalar and pseudoscalar coupled to ...
- 81
3
votes
1
answer
426
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Is there really a strong CP problem?
The strong CP problem is considered one of the major unsolved physics problems. A non-vanishing value of $\theta$ in QCD $\theta$-term violates CP-symmetry. A primary strong CP violating observable is ...
- 4,452
2
votes
1
answer
242
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Product of Lorentz invariant factors may be Lorentz non-invariant
I'm evaluating an integral and I have three cases to consider. The result of that integral must be Lorentz invariant and independent of center-of-mass momentum. One of the cases I'm certain is in fact ...
CommunityBot
- 1
0
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1
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52
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Square of the Feynman amplitude for $a +b\to c+d$ and its reverse
In quantum field theory, if a process $a +b\to c+d$ is allowed by a certain interaction Lagrangian (hermitian), the reverse process, $c+d\to a+b$, must also be allowed (as far as I understand) by the ...
- 2,772
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0
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73
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Mandelstam variables sign
I am self-studying the book "Quantum Field Theory and the Standard Model" by Schwartz, on page 99 (paragraph "Mandelstam variables"), the context is the $2\rightarrow 2$ scattering ...
- 28.4k
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1
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232
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Hypercharge of the complex scalar doublet
I often see the complex scalar doublet $Φ_A$, $A=1,2$ with the opposite hypercharge arising in the Yukawa couplings as $\tildeΦ_A = iτ{_2}_{AB}Φ_B^*$ where $τ_r$ $(r=1,2,3)$ denote isospin pauli ...
CommunityBot
- 1
13
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2
answers
1k
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Classical Dirac equation
In QFT, electromagnetism is represented by the quantum field $\hat{A}_\mu$, and fermions (matter) by the quantum field $\hat\psi$. The same kind of formalism is used for both phenomena, even if the ...
- 21
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83
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Doubt in $e^{+}e^{-}\rightarrow W^{+}W^{-}$ scattering
I am trying to understand how to compute the scattering amplitude for the process $e^{+}e^{-}\rightarrow W^{+}W^{-}$, as a reference one could look at Peskin chapter 21.
What I do not understand is ...
- 475
0
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0
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31
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QCD parton shower hard scale
Currently I'm studying parton showers from QCD and I'm having trouble with understanding how the hard scale $Q$ is related to the virtuality and energy of the parent parton. The Sudakov factor $\Delta(...
- 291
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0
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36
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Difference between jets and inclusive hadron production
I know both jets and inclusive hadron production are measured in high energy collisions. Is the difference just the way you measure it, or are there differences in the process behind them? If you ...
- 13
3
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2
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253
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Proton decays in Pati-Salam model or Georgi-Glashow model
This Pati-Salam model doesn't predict gauge mediated proton decay, according to Wikipedia.
However the Georgi-Glashow model predict gauge mediated proton decay, according to Wikipedia.
I thought the ...
CommunityBot
- 1
2
votes
1
answer
88
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Why does the mass term not violate particle number conservation in a free theory?
The Lagrangian of a free real scalar field theory is
$$ \mathcal{L} = \frac{1}{2} \partial_{\mu} \phi\; \partial^{\mu} \phi \; - \frac{1}{2} m^2 \phi^2. $$
If we decompose $\phi$ in terms of the ...
- 207k
0
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1
answer
70
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Where is antineutrino in standard model Lagrangian?
I'm somewhat confused by the content I studied in Srednicki's work, where the neutrino is described as a Majorana field. In this framework, there shouldn't technically be antineutrinos, given the ...
CommunityBot
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1
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73
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Is there a Higgs-pole like the $Z$-pole?
Why isn’t there studies of direct Higgs production like for the $Z$ boson?
Looking for future colliders, they all aim for
$$e-e+ -> HZ $$
which for me makes sense for measuring a physical Higgs but ...
- 207k
2
votes
1
answer
65
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Field redefinitions in the Higgs mechanism
Consider the Higg's mechanism for a simple $U(1)$ theory. Leaving aside the lagrangian which consists of a kinetic term for the gauge field, a covariant derivative term and the potential term for the ...
- 51.2k