All Questions
Tagged with quantum-chromodynamics scattering
32
questions
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Why there is only $t$-channel for $u+\bar d\rightarrow u+\bar d$ scattering?
I am reading Griffith's textbook on particle physics about the $u+\bar d\rightarrow u+\bar d$ scattering for QCD. On page 285, it says there is only one possible channel ($t$-channel):
Why there are ...
- 1,783
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41
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Does the scattering data, in any way, justify the simplistic picture of hadrons? [duplicate]
The structure of the neutron or the proton is extremely complicated. It is not a simple bound state of three valence quarks. However, the simplified picture allows us to explain various properties of ...
- 11.8k
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134
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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
2
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37
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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')...
1
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1
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118
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Problems understanding the BCFW recursion formula
I am currently reading through the chapter about the spinor helicity formalism in Schwartz Quantum Field Theory and Standart Model. In the chapter 27.6 (On-shell recursion) the author introduces the ...
- 387
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54
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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
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146
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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
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368
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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
1
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2
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30
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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
2
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1
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80
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Is Compton Scattering the "Abelian limit" of $qg \rightarrow qg$?
I have calculated the average over initial and sum over final states of the squared amplitude for both Compton scattering $e^-\gamma \rightarrow e^-\gamma$ (QED) and quark-gluon scattering $qg \...
- 321
1
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1
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367
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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
0
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0
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98
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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
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1
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87
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Help to derive the inequality bounds $1/4\leq F_2^{\rm en}/F_2^{\rm ep}\leq 4$ (Halzen & Martin's exercise 9.7)
The structure functions $F_2^{\rm ep}$ and $F_2^{\rm en}$ for electron-proton and electron-neutron deep inelastic scattering deduced from the model of valence quarks and sea quarks of proton and ...
- 11.8k
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1
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132
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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
2
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0
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545
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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 ...
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