General Properties on Applying the Principle of Minimum Sensitivity to High-order Perturbative QCD Predictions

TL;DR

This paper analyzes the properties of the Principle of Minimum Sensitivity (PMS) in setting the renormalization scale in high-order perturbative QCD, comparing it with the Principle of Maximum Conformality (PMC), and discusses its accuracy and convergence.

Contribution

It provides a detailed discussion on PMS properties using three QCD observables up to four-loop corrections and compares PMS with PMC, highlighting their similarities and limitations.

Findings

PMS offers a practical scale-setting method for high-energy processes.

PMS predictions align with PMC when high-order corrections are included.

PMS convergence is accidental and may not predict unknown higher-order contributions accurately.

Abstract

As one of the key components of perturbative QCD theory, it is helpful to find a systematic and reliable way to set the renormalization scale for a high-energy process. The conventional treatment is to take a typical momentum as the renormalization scale, which assigns an arbitrary range and an arbitrary systematic error to pQCD predictions, leading to the well-known renormalization scheme and scale ambiguities. As a practical solution for such scale setting problem, the "Principle of Minimum Sensitivity" (PMS), has been proposed in the literature. The PMS suggests to determine an optimal scale for the pQCD approximant of an observable by requiring its slope over the scheme and scale changes to vanish. In the paper, we present a detailed discussion on general properties of PMS by utilizing three quantities $R_{e^+e^-}$, $R_\tau$ and $\Gamma(H\rightarrow b\bar{b})$ up to four-loop QCD corrections. After applying the PMS, the accuracy of pQCD prediction, the pQCD convergence, the pQCD predictive power and etc., have been discussed. Furthermore, we compare PMS with another fundamental scale setting approach, i.e. the Principle of Maximum Conformality (PMC)... Our results show that PMS does provide a practical way to set the effective scale for high-energy process, and the PMS prediction agrees with the PMC one by including enough high-order QCD corrections, both of which shall be more accurate than the prediction under the conventional scale setting. However, the PMS pQCD convergence is an accidental, which usually fails to achieve a correct prediction of unknown high-order contributions with next-to-leading order QCD correction only, i.e. it is always far from the "true" values predicted by including more high-order contributions.