All Questions
Tagged with scattering-cross-section feynman-diagrams
36
questions
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77
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How can I calculate the cross section in general?
How can I calculate the cross-section of a process with three possible Feynman diagrams? I usually see examples with only the scattering amplitude defined by the $t$ channel, but if the scattering ...
- 11
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45
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feynman scalar integral with on-shell condition
There are many integration written down in the standard QFT textbooks for scalar integrals in the computation of matrix elements. For example, in Peskin and Schroeder, we see
$$\int \frac{d^d \ell_E}{(...
- 857
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1
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100
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Inverse muon decay on Mandl shaw- Help on $W$ boson propagator
Hello, I cannot understand why here the other term of the propagator of $W$ boson $k^{\alpha} k^{\beta}/m_{W}^{2}$ is not present, and how/if this absence is linked to the fact that we neglect terms ...
- 11
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112
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How do we interpret disconnected diagrams in scattering theory?
It is apparent that disconnected diagram contributes additional delta functions to the corresponding matrix element. For example, we consider the scalar $\phi^3$ theory and the following $2\...
- 619
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Cross-section of pair creation via vitual photons not positive definite
Consider the process of pair creation via two virtual photons, i.e. $\gamma^*(k_1)+\gamma^*(k_2) \rightarrow l^-(p_1)+l^+(p_2)$, where the dilepton (or any other fermions) can be massless or massive, ...
- 19
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2
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900
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Scalar QED differential cross section
I have a question that I'm struggling to solve. Here is the background: In scalar QED, the electron is replaced by a charged scalar particle $\phi$, and its corresponding antiparticle $\phi^{*}$, ...
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104
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How to compute unpolarized cross section for $e^−+\gamma \to e^−+\pi$
I need some help with this calculation. I have already made a few attempts but, even applying Feynman's rules for QED on the first vertex and for Yukawa interaction on the second one, I cannot figure ...
2
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2
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229
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Order of spinors in an equation for a Feynman diagram or contraction
I'm going over scattering theory in Peskin and Schroeder book, in his chapter on fermion scattering he wrote a specific contraction and the equation describing it
One thing he didn't mention is the ...
- 97
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401
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Two identical output particles in decay and scattering process in quantum field theory
I am troubled for if we need to divide the factor of $2$ for two identical output states in decay and scattering process in quantum field theory.
Consider Peskin and Schroeder's QFT book, on page 127, ...
- 1,421
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answer
563
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Scalar QED - pair annihilation into photon cross section
I just spent the last three days trying to compute the cross section of a process of pair annihilation of complex scalars to a pair of photon in scalar QED.
For some reason I don't seem to be able to ...
- 11
2
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2
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504
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Electron Muon scattering in the CM frame, question about the energy
I calculated the spin-averaged amplitude for the $e^{-}\mu^{-} \rightarrow e^{-}\mu^{-}$ scattering in the CM frame in the high energy regime($m_{e}$,$m_{\mu} \rightarrow 0$) following the hints ...
-1
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1
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Why in $e^+ e^-\rightarrow \mu^+ \mu^-$ there is only two $S_F$ propagator instead of four from path integral?
This was a homework to calculate the $e^+ e^-\rightarrow \mu^+ \mu^-$ following Peskin & Schroeder chapter 5.1. However, I got confused with the path integral aspect of the calculation.(Which was ...
- 3,256
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133
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Simplicity of the electron positron anhilation amplitude at the tree level $e^+ e^-\rightarrow \gamma \gamma$
The calculation for the electron positron annihilation to 2 photons amplitude takes up 5 pages in $\LaTeX$, and the answer is astonishingly simple
$$\mathcal{M}=-4g_e^2.$$
Even Griffiths notes this ...
user242231
4
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0
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478
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Graviton-graviton scattering in tree level. Based on a talk by Bryce DeWitt
In this talk given by Bryce DeWitt, at page 6 he mentions a problem he gave to one of his PhD students. The problem is to compute the graviton-graviton scattering amplitude in tree level approximation....
user242231
6
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2
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2k
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Elastic Proton-Proton Scattering at tree level
Hello im trying compute the Cross section of an elastic proton-proton scattering and my results are beyond terrrible and i can't figure out where my mistakes lie. I'm going to describe what i tried to ...
