All Questions
Tagged with partons particle-physics
19
questions
0
votes
0
answers
31
views
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
1
vote
2
answers
379
views
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 ...
- 11
0
votes
1
answer
61
views
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 $\bar{s}$ ...
- 119
4
votes
2
answers
752
views
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 ...
- 264
1
vote
1
answer
370
views
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
4
votes
3
answers
915
views
Why are sea quarks dominant only at low value of the Bjorken $x$ variable?
In electron proton deep inelastic scatterings, the sea quarks or gluon PDFs are only dominant at low value of $x$. Thomson explained this in his book Modern Particle Physics (see page 194) by arguing
...
- 73
3
votes
0
answers
118
views
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 ...
1
vote
1
answer
208
views
Proton Structure and Parton Distribution Function
I recently read a question about whether photons, electrons, neutrinos... are a part of the proton since there are these sea-quarks he learned about. And the answers were confusing to me because the ...
- 2,196
4
votes
1
answer
331
views
Deriving Callan-Gross from Parton Model
I want to derive the Callan-Gross relation from the parton model, not fom the Rosenbluth and Mott cross sections, but I am having some problems obtaining the textbook result. I am following M.D. ...
- 1,187
0
votes
1
answer
75
views
Transverse momentum in partonic process $\gamma^\ast q\rightarrow qg$
Let $\hat{s}:=(q+p)^2$, $\hat{t}:=(k-p)^2$, $\hat{u}:=(p-p^\prime)^2$ be the Mandelstam variables of the partonic scattering process $\gamma^\ast(q) +q(p)\rightarrow q(p^\prime)+g(k)$, where the ...
- 1,187
1
vote
0
answers
53
views
How are the structure functions in Deep inelastic scattering measured?
I've been reading lots of different textbooks on the parton model and deep inelastic scattering and the discovery of quarks, and most of the time whenever I see a plot, it's about the measurement of ...
- 700
6
votes
2
answers
2k
views
Why is it that the Callan-Gross relation predicts that quark has spin 1/2?
I'm studying deep inelastic scattering, and currently at the part where they say the Callan-Gross relation:
$$F_1 (x) = \frac{1}{2x} F_x (x)$$
where $F_1$ and $F_2$ are the dimensionless structure ...
- 700
0
votes
1
answer
323
views
What are direct experimental evidences that quarks exist? [duplicate]
Now we have very established model of quarks explaining fundamental strong interaction. What are experimental proofs for existence of quarks and what is the name of physicist which made them?
- 25
3
votes
0
answers
38
views
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
$$
f(x)=f\left(\dfrac{k}{K}\right)=\sum_j m_j^{(k)}|\langle\psi_j^{(k)}|...
- 2,921
2
votes
1
answer
150
views
Integration of the splitting function
I have a problem performing the following integration provided in the paper by Catani and Seymour (arXiv: hep-ph/9605323) page 27. Given is the integral
$$
\mathcal{V}=\int_0^1 (z(1-z))^{-\epsilon} \...
- 205