Strong coupling from an improved τ vector isovector spectral function
| Autor: | Kim Maltman, Maarten Golterman, Marcus V. Rodrigues, Diogo Boito, Wilder Schaaf, Santiago Peris |
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| Rok vydání: | 2021 |
| Předmět: |
Physics
Particle physics Isovector 010308 nuclear & particles physics FÍSICA TEÓRICA High Energy Physics::Phenomenology Hadron 01 natural sciences High Energy Physics - Experiment High Energy Physics - Phenomenology Distribution (mathematics) 0103 physical sciences Strong coupling High Energy Physics::Experiment Operator product expansion Spectral function Perturbation theory 010306 general physics Energy (signal processing) |
| Zdroj: | Repositório Institucional da USP (Biblioteca Digital da Produção Intelectual) Universidade de São Paulo (USP) instacron:USP Physical Review |
| Popis: | We combine ALEPH and OPAL results for the spectral distributions measured in $\tau\to\pi^-\pi^0\nu_\tau$, $\tau\to 2\pi^-\pi^+\pi^0\nu_\tau$ and $\tau\to\pi^-3\pi^0\nu_\tau$ decays with (i) recent BaBar results for the analogous $\tau\to K^- K^0\nu_\tau$ distribution and (ii) estimates of the contributions from other hadronic $\tau$-decay modes obtained using CVC and electroproduction data, to obtain a new and more precise non-strange, inclusive vector, isovector spectral function. The BaBar $K^- K^0$ and CVC/electroproduction results provide us with alternate, entirely data-based input for the contributions of all exclusive modes for which ALEPH and OPAL employed Monte-Carlo-based estimates. We use the resulting spectral function to determine $\alpha_s(m_\tau)$, the strong coupling at the $\tau$ mass scale, employing finite energy sum rules. Using the fixed-order perturbation theory (FOPT) prescription, we find $\alpha_s(m_\tau)=0.3077\pm 0.0075$, which corresponds to the five-flavor result $\alpha_s(M_Z)=0.1171\pm 0.0010$ at the $Z$ mass. While we also provide an estimate using contour-improved perturbation theory (CIPT), we point out that the FOPT prescription is to be preferred for comparison with other $\alpha_s$ determinations employing the $\overline{{\rm MS}}$ scheme, especially given the inconsistency between CIPT and the standard operator product expansion recently pointed out in the literature. Additional experimental input on the dominant $2\pi$ and $4\pi$ modes would allow for further improvements to the current analysis. Comment: 38 pages, 8 figures, published version |
| Databáze: | OpenAIRE |
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