Compton scattering with off-shell photon

In summary, the conversation discusses the calculation of the modulus of squared amplitude for the process e-γ*→e-γ, where the * indicates a virtual photon in an external leg. The speaker expresses their lack of experience with virtual particles in external legs and requests guidance on how to begin. The other person mentions the need for context in order to answer the question regarding the calculation of an "off-shell amplitude."
  • #1
Marioweee
18
5
Homework Statement
Compute the squared modulus of the summed amplitude over the final and initial polarizations of Compton process with a virtual photon.
Relevant Equations
.
How is it treated or what Feymann's rule applies to a virtual photon in an external leg? I would like to calculate the modulus of squared amplitude for the process

e-γ*→e-γ

where the * indicates that the photon is virtual. I've never dealt with virtual particles on a external leg and would like to know how to get started.
Thank you.
 
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  • #2
I've no idea, what the goal is. This can only be a sub-diagram in a true Feynman diagram, which in "vacuum QFT" always describes S-matrix elements with external legs symbolizing asymptotic free states. So to answer this question, we'd need the context, for which physics such an "off-shell amplitude" should be calculated.
 

FAQ: Compton scattering with off-shell photon

What is Compton scattering with an off-shell photon?

Compton scattering with an off-shell photon refers to a process where a photon that does not satisfy the usual energy-momentum relation (i.e., it is "virtual" or off-shell) interacts with a charged particle, typically an electron. This contrasts with the more common scenario where the photon is on-shell, meaning it adheres to the energy-momentum relation \( E^2 = (pc)^2 + (mc^2)^2 \) with \( m = 0 \) for photons.

How does the off-shell nature of the photon affect the Compton scattering process?

The off-shell nature of the photon introduces additional complexities into the scattering process. Since the photon does not satisfy the typical energy-momentum relation, the kinematics of the interaction are altered. This affects the scattering cross-section and the angular distribution of the scattered particles, requiring more sophisticated calculations to accurately describe the process.

Why is studying Compton scattering with off-shell photons important?

Studying Compton scattering with off-shell photons is important for understanding various high-energy and nuclear physics phenomena. Off-shell photons can appear in intermediate states of particle interactions, and their behavior can influence the outcomes of these interactions. This study is crucial for accurate modeling in quantum electrodynamics (QED) and for interpreting results from particle accelerators and other experimental setups.

What are the main theoretical tools used to analyze Compton scattering with off-shell photons?

The main theoretical tools used to analyze Compton scattering with off-shell photons include quantum field theory, particularly QED. Feynman diagrams are used to represent the interactions, and the calculations involve evaluating complex integrals over the possible intermediate states. Renormalization techniques are often employed to handle infinities that arise in these calculations.

Can Compton scattering with off-shell photons be observed experimentally?

Directly observing Compton scattering with off-shell photons can be challenging due to the virtual nature of the photons. However, indirect evidence can be obtained from experiments involving high-energy particle collisions where off-shell photons play a role in intermediate states. Advanced detectors and precise measurements are necessary to infer the presence and effects of off-shell photons in such experiments.

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