Highest loop order of experimental relevance?

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SUMMARY

The highest loop order in standard model scattering computations that contributes measurable effects in particle collider experiments is generally order-1 for most calculations and order-2 in rare cases. Notably, Higgs calculations may require NNNLO for improved accuracy, while the electron g-factor calculations utilize up to 5 loops. In Quantum Electrodynamics (QED), calculations can achieve precision up to 13 orders of magnitude with five loops, whereas Quantum Chromodynamics (QCD) converges much more slowly, with NNLO results providing approximately 0.2% to 0.5% precision. The computational limitations in QCD hinder the feasibility of higher-order calculations, making it essential to understand the implications of loop corrections.

PREREQUISITES
  • Understanding of standard model scattering computations
  • Familiarity with loop corrections in high-energy physics
  • Knowledge of Quantum Electrodynamics (QED) and Quantum Chromodynamics (QCD)
  • Basic grasp of perturbation theory and its implications in particle physics
NEXT STEPS
  • Research "NNNLO calculations in Higgs physics" for advanced accuracy techniques
  • Explore "Quantum Electrodynamics (QED) precision measurements" for insights into high-order calculations
  • Investigate "Quantum Chromodynamics (QCD) computational challenges" to understand limitations in higher-order calculations
  • Study "Perturbation theory in non-converging series" for a deeper understanding of theoretical implications
USEFUL FOR

Particle physicists, theoretical physicists, and researchers involved in high-energy physics experiments will benefit from this discussion, particularly those focused on loop corrections and precision calculations in QED and QCD.

  • #31
[URL='https://www.physicsforums.com/insights/author/urs-schreiber/']Urs Schreiber[/URL] said:
Could you point me to a good reference for this?

The original NLO paper was (Paulo) Nason, (Sally) Dawson, and (R. Keith) Ellis, around 1989. It builds on a paper a few years earlier by (John) Collins, (Dave) Soper and (Jack) Smith where they derive the relevant factorization theorems. Matteo Cacciari was giving talks about LO, NLO and the state of the art about ten years ago; if you find a conference proceedings by him that references one or both of the above papers, that's probably as good as you are going to get in one place.
 
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  • #32
Vanadium 50 said:
The original NLO paper was (Paulo) Nason, (Sally) Dawson, and (R. Keith) Ellis, around 1989. It builds on a paper a few years earlier by (John) Collins, (Dave) Soper and (Jack) Smith where they derive the relevant factorization theorems. Matteo Cacciari was giving talks about LO, NLO and the state of the art about ten years ago; if you find a conference proceedings by him that references one or both of the above papers, that's probably as good as you are going to get in one place.

Thanks. Maybe slide 12 in
  • Matteo Cacciari: "(Theoretical) review of heavy quark production" BNL 14/12/2005 (pdf)
has the kind of statement that you are referring to.
 
  • #33
I think the slides as a whole give a reasonable view of the heavy flavour state of the art. Slide 5 is a motivation for NNLO (and why N3LO may play only a minor role).
 
  • #34
Vanadium 50 said:
I think the slides as a whole give a reasonable view of the heavy flavour state of the art. Slide 5 is a motivation for NNLO (and why N3LO may play only a minor role).

Right, sorry, I meant slide 12 (I was pointing somebody else to slide 5 for another reason, and mixed up the numbers when writing here).

I am trying to pinpoint the statement which you were referring to above when you wrote:

Vanadium 50 said:
...heavy flavor production. The NLO contributions are about the same size as the LO contributions, and the scale dependence is actually worse at NLO than LO.
 
  • #35
[URL='https://www.physicsforums.com/insights/author/urs-schreiber/']Urs Schreiber[/URL] said:
I am trying to pinpoint the statement which you were referring to above

I'm sorry, but that's a little unfair. "Here's an article I found - why can't I find a statement you made in it?"

I think I did a pretty good job of pointing you in the right direction, but it may well be that a single document that has everything you want doesn't exist. But if a literature search needs to be done, I don't think I am the one who needs to do it.
 
  • #36
Vanadium 50 said:
that's a little unfair.

There is some misunderstanding here. But never mind.
 

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