All Questions
Tagged with quantum-electrodynamics particle-physics
139
questions
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How are quantum states of particles represented in particle processes?
For example, lets say we have an electron-positron annihilation scenario. What will be the density matrix representing the quantum state of the electron and the positron? What will be the density ...
- 49
3
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Literature on intense field QED
Does anyone happen to know a good book or notes on intense field QED, for example about Volkov states and the Furry picture? To give you an idea of my pre-knowledge: I am a physics graduate student ...
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85
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Electron Muon Scattering
I have been doing studying in advance for Dirac Equation and stumbled upon the math on calculating the spin-averaged amplitude $\bar{M}^{2}$ for the electron muon scattering process. Below is an ...
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A problematic equation for Dirac field:$[\psi,\hat{J_z}]=J_z\psi+i(x{\partial \psi\over\partial y}-y{\partial\psi\over\partial x})$ How is this true?
The Dirac field is quantized as:
$$\psi(x^\mu)=\int{d^3 p\over(2\pi)^3\sqrt{2\omega_p}}[a_s(p)u_s(p)e^{-ipx}+b_s^{\dagger}(p)v_s(p)e^{ipx}]$$
In the title:$$[\psi,\hat{J_z}]=J_z\psi+i(x{\partial \psi\...
- 619
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Which spinor should be used for an outgoing proton if we treated it like a point particle? $\bar{u}(p)$ (as for electron) or $v(p)$ (as for positron)
Consider the Rutherford scattering $e^-p^+ \rightarrow e^-p^+$
If a proton is a treated as a heavier positron:
$i\mathcal{M}=(-ie)\bar{u}(p_3)\gamma^{\mu}u(p_1)i\Pi_{\mu\nu}(-ie)\bar{v}(p_2)\gamma^{\...
- 619
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81
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Why is there a $u$ in the middle of the feynman diagram for a quark and an antiquark annihilating?
There is a feynman diagram in chapter 2 of Griffiths Introduction to elementary particles, where a pair annihilation is taking place. I am confused as before it was written that internal lines are ...
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Spin magnetic dipole moment of electron not an invariant with acceleration?
Since the energy of the electron at rest can be calculated by:
$$
E_e=\frac{h c}{ \lambda_e}
$$
where $\lambda_e$ is the Compton wavelength value of the electron at rest, $h$ the Planck constant and $...
- 4,170
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432
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Feynman diagram of muon pair production [duplicate]
Hi to everyone. I don't understand why the diagram in which final antimuon and muon are exchanged is not possible (so having in the upper part positron and muon, downwards electron and antimuon). It ...
21
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1
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Are photons actually particles at all?
I just read this answer to "What exactly is a Photon?" which has me a bit confused. It seems to be arguing that "photon" is just a catch-all term for any sort of interaction with ...
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2
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2
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177
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How can QFT perturbation be used for electron-positron scattering?
I'm studying scattering and perturbation theory in QFT from Peskin and Schroeder book. After all the calculations and theory developing, they made a calculation for $$e^-e^+\to\mu^-\mu^+$$ scattering. ...
- 97
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3
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87
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Problem with the vacuum energy upon quantization of the EM field in Lorenz gauge
There seems to be an issue arising concerning the vacuum energy of the EM field after quantizing in Lorenz gauge.
As usual, we consider an extra gauge-fixing term in the Lagrangian of the form $-\frac{...
- 115
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130
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How soft photons carry away energy
While studying the infrared traces, I came across the following Feynman diagram:
This diagram shows the braking radiation and the radiation correction of a soft photon. There are three vertices in ...
- 51
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584
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Electron–positron annihilation (Quantum electrodynamics)
I'm trying to learn a bit about quantum particles interactions and I've found something in Wikipedia that I find confusing. There are two different examples with different results about the same ...
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65
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What is the angle between two $b$-quarks when a Higgs boson decays to a $b$-quark pair, in the rest frame of Higgs boson?
I am generating events of $ep -> Xjv$, ($j$ is a jet, and $v$ shows a neutrino) where $X$ particle decays to a $b$-quark pair. I am going to calculate the angle between two b-quarks in the rest ...
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Has been the spin magnetic dipole moment value of the free electron to be Lorentz invariant ever experimentally verified?
As far as I know all experiments measure the rest value of the spin magnetic dipole moment of a free electron either indirectly at relativistic speeds near the speed of light measuring for example the ...
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