Understanding Hadron Structure through Electron-Positron Collisions

In summary, Halzen and Martin describe the use of virtual photons obtained through the annihilation of e+ and e- beams to study hadron structure. Figure 1.11(b) shows a diagram of this process, but there is a discrepancy with the direction of the positron arrow. The authors explain that this depends on convention and is inconsistent with their e+e- annihilation diagram. They also mention that the photon produced in this process is at rest, meaning it has no momentum in the lab. The direction of time and energy in the diagram is also clarified.
  • #1
maverick280857
1,789
4
Hi,

Halzen and Martin, on page 18 of their book, describe the resolution of hadron structure using virtual photons obtained by annihilating e+ and e- beams.

In Figure 1.11(b), isn't the positron arrow shown wrongly? It seems to be moving forward in time. (Or maybe I'm just being picky here?)

They go on to say,

Colliding very high-energy electron and positron beams also provides us with an extremely "clean" technique to probe quarks (see Fig. 1.11b). The photon, produced at rest by e+ and e- beams colliding head on, can decay into a qqbar pair as shown in the pictuire.

What does "produced at rest" mean?

Thanks in advance!
 
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  • #2
maverick280857 said:
In Figure 1.11(b), isn't the positron arrow shown wrongly? It seems to be moving forward in time. (Or maybe I'm just being picky here?)
It depends on one's convention, but it is inconsistent with their e+e- annihilation diagram 6.13
maverick280857 said:
What does "produced at rest" mean?
It means it has no momentum in the lab.
 
  • #3
humanino said:
It depends on one's convention, but it is inconsistent with their e+e- annihilation diagram 6.13
It means it has no momentum in the lab.

Thanks, I guess time runs vertically here.
 
  • #4
maverick280857 said:
Thanks, I guess time runs vertically here.

Actually I was confused. There is no inconsistency. Time always flows horizontally from left to right it seems. Also, it seems the arrow always points in the direction of positive energy.
 
  • #5
Nah, the problem is it's not a Feynman diagram, its a particle flow diagram. The arrows here basically correspond to particle flow. They're just trying to show that an e+ coming in and an e- coming in annihilate.
 

1. What is the main goal of resolving hadron structure?

The main goal of resolving hadron structure is to understand the fundamental building blocks of matter and how they interact with each other. This includes understanding the internal structure of hadrons, which are particles made up of quarks and gluons.

2. How do scientists study the structure of hadrons?

Scientists use various methods, such as scattering experiments and theoretical calculations, to study the structure of hadrons. These experiments involve accelerating particles and colliding them with hadrons to observe how they interact and gather information about their internal structure.

3. What have scientists discovered about hadron structure so far?

Scientists have discovered that hadrons are made up of even smaller particles called quarks and gluons. They have also found that the interactions between these particles are governed by the strong nuclear force, one of the four fundamental forces of nature.

4. Why is understanding hadron structure important?

Understanding hadron structure is important because it helps us to understand the behavior of matter at a fundamental level. It also has practical applications, such as in the development of new technologies and medicines.

5. What are some current challenges in resolving hadron structure?

One current challenge is to reconcile the experimental data with theoretical predictions. Another challenge is to understand the role of confinement, which is the phenomenon that prevents quarks and gluons from being observed as individual particles. Additionally, scientists are working to better understand the complex interactions between quarks and gluons within hadrons.

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