All Questions
Tagged with partons quantum-field-theory
22
questions
1
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0
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36
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Derivation of the Equivalent Photon Approximation in Peskin and Schroeder
I am trying to reproduce the equivalent photon approximation as discussed in chapter 17.5 in Peskin and Schroeder but cannot justify equation (17.93).
The process we are considering is the scattering ...
- 337
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
0
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0
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96
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Is the pion valence PDF symmetric?
The positive-pion $\pi^+$ is comprised of 1 valence up-quark and 1 valence anti-down-quark. Assuming isospin symmetry, the parton distribution functions (PDFs) for these two valence quarks should be ...
- 5,371
1
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45
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How to derive quark-antiquark parton distribution relation?
This is kind of similar to this post here How to define the parton distribution function of the antiquark? with no response.
I basically want to derive the following; $f_q(x) = -f_{\bar{q}}(-x)$ where
...
- 391
2
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answers
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What are the differences between FFN, VFN, GMVFN and ZMVFN PDF schemes in QCD?
What are the differences between the fixed flavour number (FFN), variable flavour number (VFN), general-mass variable flavour number (GMVFN) and zero-mass variable flavour number (ZMVFN) schemes for ...
- 1,187
1
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0
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51
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What are extrinsic and intrinsic flavour production?
In terms of Feynman diagrams, what are extrinsic and intrinsic flavour production?
See for example this paper this paper (p.2).
- 1,187
1
vote
1
answer
370
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OPE leading twist = collinear factorisation?
The operator product expansion systematically expands QFT interactions in terms of a sum of local operators.
Is the leading twist of this expansion identifiable with collinear factorisation and, if so,...
- 3,569
3
votes
0
answers
118
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Textbook for parton distributions?
Are there any textbooks, or good pedagogical review articles, on the subject of parton distributions? I'm looking for such sources that cover all the standard topics, such as:
Generalized parton ...
2
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0
answers
47
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How to define the parton distribution function of the antiquark?
So I can define the quark distribution function within a hadron as
$$
f_{\psi/h}(x)=\frac{1}{2}\int\frac{dz^-}{2\pi}e^{ixP^+z^-}
\langle h(p)|\bar{\psi}(0)\gamma^+\psi(z^-)|h(p)\rangle|_{z^2=0}
$$
...
- 115
7
votes
2
answers
364
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Does the path of a Wilson line in a quark-correlator matter?
Consider a gauge-invariant quark correlation function nested inside an arbitrary state $|p\rangle$
$$\langle p |\bar \psi(z)_{\alpha,a}\left( W_{\Gamma}(z,0)\right)_{ab}\psi(0)_{\beta,b}|p\rangle \...
- 5,371
0
votes
1
answer
61
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Transverse momentum in the parton model
Why is it so important that the partons in the parton model have low transverse momenta? And transverse to what anyway? I mean, basically one looks to justify breaking the hadronic subgraph in hadron-...
- 1,187
2
votes
1
answer
146
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Why small $x$ corresponds to high energy process?
I just start to study Quantum Chromodynamics, I read in some references that small $x$ corresponds to process of high energy, but I cannot find a straightforward explanation.
In the case of electron ...
- 68
3
votes
0
answers
70
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Polarized structure functions and Bjorken sum rule
I'm trying to understand what the Bjorken sum rule and the polarized structure functions entering it are. I will use equation (2.3) here as a reference for asking the question.
In Peskin, I've only ...
- 2,921
3
votes
0
answers
38
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Parton distribution function in terms of Fock space kets
To my understanding, I can (at least, formally) express the (unnormalized) PDF for a certain constituent of a composite state as
$$
f(x)=f\left(\dfrac{k}{K}\right)=\sum_j m_j^{(k)}|\langle\psi_j^{(k)}|...
- 2,921
0
votes
0
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177
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Question about DGLAP evolution equation
I am reading chapter 32.2 of Schwartz's QFT book, where he defines the renormalized PDFs $f_i(x, \mu)$. This leads to an equation (32.48), which relates PDFs at different scales $\mu, \mu_1$:
$f_i(x,\...
- 1,129