Questions tagged [partons]
A parton is a gluon, quark or antiquark in the eponymous model of scattering involving hadrons. In the hadron's infinite-momentum frame, incoming particles will be scattered instantaneously and incoherently, reducing the problem to a simple kernel convolved with parton distributions, at a particular physical scale (as probed by the inverse of the momentum transfer).
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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(...
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Quark charges - parton-distribution function - factor 5/18
I got the following from Thomson’s Modern Particle Physics and some other sources.
The factor 5/18 distinguishing electron-DIS and neutrino scattering experiments is a basic proof for quarks and their ...
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What is a polarized/unpolarized parton?
In QCD physics, certain partonic distributions like Generalized Parton Distributions (GPDs) and Transverse Momentum Distributions (TMDs) are defined for the case where the parton is either unpolarized,...
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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 ...
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Parton, detector and particle level at LHC [closed]
What is the difference between parton, detector and particle level in high energy physics?
I found a similar question but I couldn't understand the explanation for detector and particle level given ...
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Paper showing evidence for Callan-Gross Relation
I am getting ready for a presentation and want to show a plot showing experimental evidence for the Callan-Gross relation. Are there any papers plotting this beyond 1970 across different $Q^2$ or ...
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Parton Distribution Functions - Antiquarks?
In all the PDF plots that I have seen so far (e.g. https://arxiv.org/abs/1111.5452 Fig. $3$ and $4$) the PDFs for sea or charm quarks contained only the strange or charm quark, but not the $\bar{s}$ ...
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Physical interpretation of hadron distribution amplitudes
A parton fragmentation function can be interpreted as the probability that a final state hadron originated from that particular hadron.
A parton distribution function can be interpreted as the ...
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Meaning of $\gamma^\pm$ in Parton Fragmentation Functions
I was just working through the paper Parton fragmentation functions and came across equation 12.
What do $\gamma^{+}$ and $\gamma^{-}$ mean? The text doesn't explain this at all.
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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
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Collinear factorisation in QCD: why can we multiply probabilities?
In the collinear factorisation equation for a QCD cross-section, schematically
$$
\sigma_{AB\to X}
=
f^A_a \otimes \hat{\sigma}_{ab\to X} \otimes f^B_b
,
$$
we essentially convolute the probability ...
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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 ...
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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).
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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,...
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Is $\mu$ the renormalization or factorization scale in the DGLAP equations?
The DGLAP equations read
$$\frac{\partial f_i(x,\mu^2)}{\partial\ln\mu^2}=\sum_j\int^1_x\frac{dz}{z}P_{ij}(z,\alpha_s(\mu^2))f_j\left(\frac{x}{z},\mu^2\right),$$
where the $f_i$ are the parton ...
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