All Questions
Tagged with quantum-chromodynamics scattering
32
questions
1
vote
1
answer
215
views
Elimination of three gluon vertex
I am reading this paper by Dixon, where it is mentioned that one can diagrammatically compute the colour factor of certain Feynman graphs, such as shown in figure 1, where they expand a three gluon ...
- 302
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
1
answer
87
views
Notation: Dividing by a partial differential
Setup
Hi, I am working on a DIS scattering problem in the Light Cone Gauge, and this has me needing to calculate the currents. In doing this, I have come across the following equation
$$
t^a \...
1
vote
1
answer
187
views
Drell-Yan process and factorization scale
What is the most relevant choice for the factorization scale of the Drell-Yan process? Can it be the invariant mass at the reaction threshold?
- 8,901
3
votes
0
answers
356
views
Bjorken Scaling and the Parton Model
It is often said that Bjorken scaling of the deep inelastic structure functions
\begin{equation}
\nu W_2(\nu ,Q^2)\rightarrow F(x)
\end{equation}
(where $Q^2$ is the virtuality of the photon, $\nu=\...
- 2,270
2
votes
1
answer
370
views
Parton distribution function and factorization scale
Consider some deep inelastic scattering $y f\to y f$, where $f$ is a parton inside a nucleon $N$, and $y$ is some particle. The cross-section is then
$$
\sigma_{\text{DIS}} = \int dx f_{N/f}(x,Q^{2})\...
- 8,901
7
votes
1
answer
338
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NMHV 5 Gluon Scattering (Elvang and Huang, Ex 3.11)
In Elvang and Huang's Scattering Amplitudes in Gauge Theory and Gravity, Exercise (3.10) (Exercise (3.11) in the printed version) asks the reader to construct the NMHV scattering amplitude of five ...
- 421
4
votes
1
answer
1k
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Callan-Gross relation validity
The inelastic electron-proton scattering cross section can be written as
$$\frac{d\sigma}{dE_2d\Omega}=\frac{\alpha^2}{4*E_1\sin^4{\frac{\theta}{2}}}(W_2\cos^2{{\frac{\theta}{2}}}+2W_1\sin^2{{\frac{\...
- 263
7
votes
1
answer
276
views
What is the mathematical motivation for complexifying momenta in BCFW?
One of the first steps in obtaining the on-shell BCFW recursion relations is complexifying the momenta of the external particles. Now complexifying things is not unprecedented (the dispersion program ...
- 1,124
4
votes
2
answers
186
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How to compute scattering amplitude $\gamma\pi^+\to\pi^+\pi^0$
I wish to find the amplitude for process $\gamma\pi^+\to\pi^+\pi^0$ at low energies. I am familiar with the basic concepts and techniques of QFT but have never dealt with the scattering processes ...
- 1,586
2
votes
1
answer
5k
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Altarelli-Parisi Splitting Function $P_{qq}(z)$ vanishing integral if and only if quark flavour sum rules and equivalence
Question 1: I believe both questions are in the context of Deep Inelastic Scattering. I've been given the expression for $F_{2}^{ep}(x)=(\frac{2}{3})^2[u(x)+\bar{u}(x)]
+(\frac{1}{3})^2[d(x) + \bar{d}(...
- 23
3
votes
0
answers
194
views
Conversion of QCD cross section formula
I'm writing a program to calculate NLO cross sections for semi-inclusive high-$p_T$ pion production in proton-proton-collisions for my bachelor thesis.
I've got a paper describing the production ...
- 337
16
votes
4
answers
4k
views
Is forward scattering = no scattering?
What is forward scattering? If it is equivalent to no scattering, then why not call it "no scattering"?
- 5,569
19
votes
2
answers
3k
views
Why Cronin Effect Happens?
I'm looking for explanation on Cronin effect but unfortunately there's no Wikipedia entry or self-contained paper to start from. The statement of this effect is that:
"At leading order, multiple ...
- 1,707
7
votes
1
answer
2k
views
A certain gluon scattering amplitude
I am stuck with this process of calculating the tree-level scattering amplitude of two positive helicity (+) gluons of momentum say $p_1$ and $p_2$ scattering into two gluons of negative (-) helicity ...
- 4,619