All Questions
Tagged with quantum-chromodynamics scattering
13
questions with no upvoted or accepted answers
3
votes
0
answers
370
views
What is meant by the "Leading Log Approximation" in the context of the steep rise in gluon distribution at small bjorken x?
I am taking a course in QCD, and we're learning about Regge Theory, Pomeron exchange and structure functions.
I want to know what is meant by the leading log approximation in the context of the gluon ...
- 316
3
votes
0
answers
70
views
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
356
views
Bjorken Scaling and the Parton Model
It is often said that Bjorken scaling of the deep inelastic structure functions
\begin{equation}
\nu W_2(\nu ,Q^2)\rightarrow F(x)
\end{equation}
(where $Q^2$ is the virtuality of the photon, $\nu=\...
- 2,270
3
votes
0
answers
194
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Conversion of QCD cross section formula
I'm writing a program to calculate NLO cross sections for semi-inclusive high-$p_T$ pion production in proton-proton-collisions for my bachelor thesis.
I've got a paper describing the production ...
- 337
2
votes
0
answers
38
views
How to derive Collinear amplitude proportional to Born amplitude
In the collinear limit, the squared matrix element factorises into (for partons 4 and 5 going collinear)
\begin{eqnarray}
\overline{\sum}|M_3(1+2 \to 3+4+5)|^2 \approx \overline{\sum}|M_2(1+2 \to 3+4')...
2
votes
0
answers
551
views
Colour-ordering formula of QCD amplitudes (tree-level)
I have been studying colour-ordered amplitudes and spinor helicity formalism for a while. It is now apparent to me that I do not fully understand the 'master' formula which allows us to relate the ...
- 155
1
vote
0
answers
135
views
How do I calculate the Altarelli-Parisi splitting function for $g \rightarrow q\bar{q}$?
I'm trying to calculate the Altarelli-Parisi splitting function in the collinear limit for a gluon splitting into a quark-antiquark pair, but I keep getting stuck. Let $p$ and $k$ be the momenta for ...
- 43
1
vote
0
answers
147
views
Soft-gluon of scattering amplitude
The question from Scattering Amplitudes in Gauge Theory and Gravity page 46, equation (2.120) from which I can't get a consistent formula.
I just calculate A3(gff) which two fermion and one gluon $A_n\...
- 11
1
vote
2
answers
30
views
Understanding Jet Clustering: Why is only $p_{T}$ used?
Let's only consider iterative jet clustering algorithms. Famous ones are the $k_{T}$ ($p = 1$), anti-$k_{T}$ ($p = -1$) and Cambridge/Aachen ($p = 0$) jet reconstruction algorithms.
All these ...
user248824
1
vote
1
answer
370
views
Deep inelastic scattering (DIS) and handbag diagram
Here, in page 11, you can see the so-called 'handbag' diagram that explains how a virtual photon emitted in a deep inelastic scattering (DIS) process interacts with a parton.
I'm going to use this ...
- 1,597
1
vote
1
answer
133
views
Confusion among channel $u$ and channel $t$ in exclusive reactions
In the this paper (https://arxiv.org/abs/1203.4392), on page 2 it is said that
Since DVCS amplitude is symmetric under $s \leftrightarrow u$ channel crossing, the CFFs and $^{S}C^i_{\cdots}$ ...
- 1,597
0
votes
0
answers
55
views
Evolution of the proton without external interactions
I've been thinking about the possibility of the proton evolving without external interactions and came up with the following problem. Let's say we have an isolated proton and therfore the Lagrangian ...
- 1,597
0
votes
0
answers
99
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Deep inelastic electron-proton scattering amplitude
In 'QCD and collider Physics' book by Ellis, Stirling and Webber, chapter 4.2 'The parton model from field theory' there is this equation for the amplitude of the process $e^- (k) P \rightarrow e^- (k^...
- 1,597