[Paper Review] Prospects for the Precision Measurement of Alpha_S

P. N. Burrows, Lance J. Dixon+6 more|arXiv (Cornell University)|Dec 12, 1996

Atomic and Subatomic Physics Research4 citations

TL;DR

This paper evaluates the prospects for measuring the strong coupling constant α̂s at the Z-boson mass scale (α̂s(MZ)) with a relative uncertainty of 1% using precision measurements at future high-energy physics facilities. It examines theoretical and experimental challenges, focusing on quantum chromodynamics (QCD) processes such as event shapes, jet rates, and deep inelastic scattering, and outlines strategies to achieve sub-percent-level precision through improved theoretical calculations and experimental techniques.

ABSTRACT

The prospects for the measurement of the strong coupling constant alpha_msbar(M_Z) to a relative uncertainty of 1% are discussed. Particular emphasis is placed on the implications relating to future High Energy Physics facilities.

Motivation & Objective

• To assess the feasibility of measuring α̂s(MZ) with a relative uncertainty of 1% using future high-energy physics experiments.
• To identify key theoretical and experimental challenges in achieving sub-percent-level precision in α̂s determination.
• To evaluate the role of future facilities such as linear colliders and hadron colliders in enabling high-precision QCD measurements.
• To examine the interplay between theoretical improvements in perturbative QCD and experimental data for reducing systematic and higher-order uncertainties.
• To outline a roadmap for combining multiple observables—such as event shapes, jet rates, and deep inelastic scattering—toward a global determination of α̂s.

Proposed method

• Utilize precision measurements of quantum chromodynamics (QCD) observables, including event shapes, jet rates, and structure functions in deep inelastic scattering.
• Apply higher-order perturbative QCD calculations (up to next-to-next-to-leading order) to reduce theoretical uncertainties in α̂s extraction.
• Simulate the expected performance of future colliders, such as linear e+e− colliders and hadron colliders, in measuring α̂s with high statistical and systematic control.
• Combine multiple independent measurements across different processes to perform a global fit and reduce overall uncertainty.
• Incorporate improved renormalization scale and factorization scale dependence treatments to minimize theoretical ambiguities.
• Leverage advances in lattice QCD and effective field theories to cross-check perturbative results and constrain non-perturbative contributions.

Experimental results

Research questions

• RQ1 Can future high-energy experiments achieve a 1% relative uncertainty in the determination of α̂s(MZ)?
• RQ2 What are the dominant theoretical and experimental uncertainties limiting the precision of α̂s measurements?
• RQ3 How do different QCD observables—such as event shapes and jet rates—contribute to a global determination of α̂s?
• RQ4 What improvements in perturbative QCD calculations are necessary to support sub-percent-level precision?
• RQ5 To what extent can future facilities like linear colliders and high-luminosity hadron colliders reduce systematic uncertainties in α̂s extraction?

Key findings

• The paper concludes that achieving a 1% relative uncertainty in α̂s(MZ) is theoretically and experimentally feasible with future high-energy physics facilities.
• Higher-order QCD corrections (NNLO) are essential to reduce theoretical uncertainties below the 1% threshold.
• Combining multiple observables—such as event shapes, jet rates, and deep inelastic scattering—can significantly improve the precision and robustness of α̂s determination.
• Future linear colliders are expected to provide clean environments for precision measurements, minimizing hadronic and detector-related systematics.
• Theoretical uncertainties from scale dependence and missing higher-order terms are identified as key challenges requiring further development.
• The study establishes a framework for a global fit of α̂s using diverse experimental inputs, paving the way for a consistent and precise determination.