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Strong running coupling at τ and Z(0) mass scales from lattice QCD
B Blossier1, Ph Boucaud, M Brinet
1Laboratoire de Physique Théorique, Université de Paris XI, Bâtiment 210, 91405 Orsay Cedex, France.
Physical Review Letters
|September 26, 2012
Summary
This study computed the running strong coupling constant using lattice quantum chromodynamics (QCD) with four quark flavors. Results align with experimental data, improving accuracy with the inclusion of charm quarks.
Area of Science:
- High Energy Physics
- Quantum Chromodynamics
- Computational Physics
Background:
- The strong coupling constant, a fundamental parameter in quantum chromodynamics (QCD), describes the strength of the interaction between quarks and gluons.
- Accurate determination of the running strong coupling is crucial for theoretical predictions in particle physics and for comparing with experimental measurements.
- Previous lattice QCD calculations often omitted or approximated the effects of heavier quarks, potentially impacting the precision of the running coupling's determination.
Purpose of the Study:
- To perform the first lattice QCD calculation of the running strong coupling constant incorporating dynamical light (u, d, s) and charm (c) quarks.
- To renormalize the ghost-gluon coupling using the momentum-subtraction Taylor scheme.
- To provide precise estimates of the strong coupling at different energy scales, specifically at m(τ)^2 and m(Z)^2.
Main Methods:
- Utilizing lattice quantum chromodynamics (LQCD) simulations with dynamical u, d, s, and c quarks.
- Employing the ghost-gluon coupling as the observable for renormalization.
- Renormalizing the coupling in the momentum-subtraction Taylor scheme.
- Extrapolating results to the continuum limit and performing the running to the desired scales.
Main Results:
- The first computation of the running strong coupling constant from lattice QCD data including dynamical u, d, s, and c quarks.
- Estimates for α(MS[over ¯])(m(τ)^2) and α(MS[over ¯])(m(Z)^2) obtained are in excellent agreement with experimental results.
- Demonstration that including a dynamical charm quark enhances the reliability and safety of the running coupling calculation.
Conclusions:
- The inclusion of dynamical charm quarks in lattice QCD calculations is essential for a precise determination of the running strong coupling constant.
- The momentum-subtraction Taylor scheme provides a robust framework for renormalizing the ghost-gluon coupling.
- This work validates lattice QCD as a powerful tool for calculating fundamental parameters of the Standard Model, consistent with experimental observations.
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