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Prospects for the Precision Measurement of Alpha_S

P. N. Burrows, L. Dixon, A. X. El-Khadra, J. W. Gary, W. Giele, D. A. Harris, S. Ritz, B. A. Schumm

TL;DR

The paper surveys the prospects for measuring $\alpha_S$ to about 1% precision, emphasizing how diverse high-energy physics facilities and theoretical advances could enable cross-validated determinations. It analyzes four main approaches—DIS through $F_3$ evolution, GLS and Bjorken sum rules, lattice QCD using quarkonium spectra, and $e^+e^-$ jet observables—along with potential high-energy hadron collider strategies, assessing their NNLO requirements and systematic limitations. It highlights the complementary nature of low- and high-$Q^2$ probes and argues that a combination of DIS, lattice, and collider measurements can robustly determine $\alpha_S(M_Z)$ with sub-percent accuracy, given future facilities and improved theory. The work underscores that achieving 1% precision will significantly impact Standard Model tests, electroweak unification constraints, and beyond-Standard-Model searches through precise knowledge of the QCD coupling evolution.

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.

Prospects for the Precision Measurement of Alpha_S

TL;DR

The paper surveys the prospects for measuring to about 1% precision, emphasizing how diverse high-energy physics facilities and theoretical advances could enable cross-validated determinations. It analyzes four main approaches—DIS through evolution, GLS and Bjorken sum rules, lattice QCD using quarkonium spectra, and jet observables—along with potential high-energy hadron collider strategies, assessing their NNLO requirements and systematic limitations. It highlights the complementary nature of low- and high- probes and argues that a combination of DIS, lattice, and collider measurements can robustly determine with sub-percent accuracy, given future facilities and improved theory. The work underscores that achieving 1% precision will significantly impact Standard Model tests, electroweak unification constraints, and beyond-Standard-Model searches through precise knowledge of the QCD coupling evolution.

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.

Paper Structure

This paper contains 14 sections, 15 equations, 4 figures, 2 tables.

Table of Contents

  1. Introduction
  2. Deep Inelastic Scattering
  3. DIS Nucleon Structure Functions
  4. Methods used to Determine $\alpha_{S}$ from DIS Structure Functions
  5. Future Prospects for a Precise $\alpha_{S}$ Measurement from DIS
  6. Conclusion for a Precise $\alpha_{S}$ Result from DIS
  7. The Hadron Spectrum
  8. Determination of the Lattice Spacing and the Quarkonium Spectrum
  9. Definition of a Renormalized Coupling
  10. Sea Quark Effects
  11. Conclusions
  12. Electron-Positron Annihilation
  13. $pp$ ($p\overline{p}$) Collisions
  14. Conclusions

Figures (4)

  • Figure 1: Summary of current accurate measurements of $\alpha_{S}$, by technique. The $\alpha_{S}$ measurements are based on perturbative QCD, except where otherwise noted.
  • Figure 2: The 1P-1S splitting as a function of the 1S mass (statistical errors only) from Ref. us; $\Box$: ${\cal O}(a^2)$ errors; $\times$: ${\cal O}(a)$ errors.
  • Figure 3: A comparison of lattice QCD results for the $b\bar{b}$ spectrum (statistical errors only). --: Experiment; $\Box$: FNAL us; $\circ$: NRQCD ($n_f=0$) nrqcd_spec; $\bullet$: NRQCD ($n_f=2$) nrqcd_als; $\diamond$: UK(NR)QCD uknrqcd; $*$: SCRI sloan.
  • Figure 5: The preliminary CDF and D0 Run Ib data compared to NLO QCD using CTEQ4M parton distributions. Experimental points normalized as indicated. This figure is reproduced from Reference jetet.