Drell Yan process and divergencies

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In summary, the DY process with NLO computation requires the renormalization of physical parameters to get rid of UV divergences, while IR divergences can be canceled through a combination of real gluon and quark emission and renormalization of PDFs. IR divergences include both soft and collinear emissions, and both the real emission and renormalization methods are necessary to eliminate them.
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Jodahr
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Hello @ all,

I have a few short questions. If we compute the DY process with NLO computation we get rid of the UV divergencies with renormalization of some physical parameters like the field, mass, coupling. The IR divergencies cancel somehow with the real gluon and quark emission. But not all of them. So, my question:

1. Is only soft gluon and quark emission called IR? Or does IR include collinear divergencies?
2. in a proton collison (pp-> l \bar{l}) which part of the divergencies is canceld by the real emission part, which by renormalization of the PDFs?

while considering all the particles as massless.

Please..I need some help to classify the different types...except of the UV part...and with which method we get rid of it...Thanks!
 
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Thank you for your questions regarding the DY process and its computation with NLO. To answer your questions:

1. IR (infrared) divergences refer to all divergences that arise from soft and/or collinear emissions in the final state. Soft emissions refer to particles with very low energy, while collinear emissions refer to particles traveling in almost the same direction. Both types of emissions can lead to divergences in the calculation, and therefore need to be taken into account in the renormalization process.

2. In a proton collision, both the real emission part and the renormalization of PDFs play a role in canceling the IR divergences. The real emission part takes into account the contributions from soft and collinear emissions, while the renormalization of PDFs takes into account the contributions from the initial state partons. Both are necessary to fully cancel the IR divergences and obtain a physically meaningful result.

I hope this helps clarify the different types of divergences and the methods used to eliminate them. If you have any further questions, please don't hesitate to ask. Thank you for your interest in this topic.
 

1. What is the Drell Yan process?

The Drell Yan process is a scattering process in which a quark and an anti-quark annihilate and produce a lepton-antilepton pair. This process was first proposed by Sidney Drell and Tung-Mow Yan in 1970 and has since been observed in various high energy experiments.

2. How does the Drell Yan process contribute to our understanding of the strong interaction?

The Drell Yan process is one of the ways in which we can study the strong interaction, also known as the strong nuclear force, which is responsible for holding quarks together in protons and neutrons. By studying the properties of the lepton-antilepton pair produced in this process, we can gain insights into the structure of the quarks and the strong interaction itself.

3. What are divergencies in the context of the Drell Yan process?

In quantum field theory, divergencies refer to mathematical expressions that become infinite when certain parameters approach certain values. In the context of the Drell Yan process, divergencies can arise in calculations involving virtual particles, which are particles that exist for a brief moment as part of the scattering process. These divergencies need to be carefully accounted for in order to obtain accurate predictions from the theory.

4. How do scientists deal with divergencies in the Drell Yan process?

There are various mathematical techniques, such as renormalization, that are used to deal with divergencies in quantum field theory. These techniques involve redefining certain parameters in the theory in order to cancel out the infinities and obtain physically meaningful results. In the case of the Drell Yan process, scientists use these techniques to make predictions that can be compared with experimental data.

5. What are some potential future developments in the study of the Drell Yan process?

Scientists are constantly working to improve our understanding of the Drell Yan process and its role in the strong interaction. Some potential future developments may include higher precision measurements of the properties of the lepton-antilepton pairs produced in this process, as well as theoretical advancements in our understanding of the strong interaction and its behavior at high energies.

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