Discussion Overview
The discussion revolves around the highest loop order in standard model scattering computations that contributes measurable effects in particle collider experiments. Participants explore the necessary loop corrections for high energy physics, examining both theoretical and experimental aspects.
Discussion Character
- Exploratory
- Technical explanation
- Debate/contested
- Mathematical reasoning
Main Points Raised
- One participant suggests that loop corrections are generally order-1 for most computations and order-2 in rare cases, questioning if there are notable exceptions.
- Another participant mentions that some Higgs calculations are performed at NNNLO and that calculations for the electron g-factor involve up to 5 loops, although this is not a collider experiment.
- A question is raised about the order up to which perturbation series can be expected to improve before diverging, with a participant noting that low-energy QCD may have already reached this point.
- Estimates are provided regarding QED contributions, suggesting they stop getting smaller around order 430, although the problem arises earlier in high-energy QCD.
- Concerns are expressed about the subtlety of determining where an asymptotic series starts to diverge, with references to mathematical series that decrease but do not converge to a value.
- Participants discuss the implications of high-order contributions being tiny, particularly in the context of the g-2 calculation, and the relevance of these contributions to experimental results.
- There is a discussion about the uncertainty of theoretical predictions compared to experimental measurements, with specific values provided for the g-2 case.
- One participant emphasizes that the smallness of contributions does not necessarily imply they improve the match to experimental results, raising questions about the behavior of contributions beyond certain orders.
Areas of Agreement / Disagreement
Participants express multiple competing views regarding the highest relevant loop order and the behavior of perturbation series. There is no consensus on the exact order beyond which contributions may diverge or fail to improve theoretical predictions.
Contextual Notes
Participants note that the calculations and estimates discussed depend on specific measurements and theoretical frameworks, with unresolved aspects regarding the behavior of asymptotic series and the implications of high-order corrections.