English

QCD condensates and $\alpha_s$ from $\tau$-decay

High Energy Physics - Phenomenology 2025-04-22 v3

Abstract

We improve the determinations of the QCD condensates within the SVZ expansion in the axial-vector (A) channel using the ratio of Laplace sum rule (LSR) R10A(τ){\cal R}_{10}^A(\tau) within stability criteria and τ\tau-like higher moments Rn,A{R}_{n,A} within stability for arbitrary τ\tau-mass squared s0s_0. We find the same violation of the factorization by a factor 6 of the four-quark condensate as from e+ee^+e^- \to Hadrons data. One can notice a systematic alternate sign and no exponential growth of the size of these condensates. Then, we extract αs\alpha_s from the lowest τ\tau-decay like moment and find: αs(Mτ)VA=0.3135(83)\alpha_s(M_\tau)\vert_{V-A}=0.3135(83) (FO) and 0.3322 (81) (CI) leading to: αs(MZ)VA=0.1177(10)fit(3)evol.\alpha_s(M_Z)\vert_{V-A}=0.1177(10)_{fit}(3)_{evol.} (FO) and 0.1200(9)fit(3)evol.0.1200(9)_{fit}(3)_{evol.}\,(CI). We extend the analysis to the V--A channel and find: αs(Mτ)VA=0.3135(83) \alpha_s(M_\tau)\vert_{V-A}=0.3135(83) (FO) and 0.3322 (81) (CI) leading to: αs(MZ)VA=0.1177(10)fit(3)evol.\alpha_s(M_Z)\vert_{V-A}=0.1177(10)_{fit}(3)_{evol.} (FO) and 0.1200(9)fit(3)evol.0.1200(9)_{fit}(3)_{evol.}\,(CI). We observe that in different channels (e+ee^+e^-\to Hadrons, \, A,\,V-A), the extraction of αs(Mτ)\alpha_s(M_\tau) at the observed τ\tau-mass leads to an overestimate of its value. Our determinations from these different channels lead to the mean: αs(Mτ)=0.3140(44) \alpha_s(M_\tau)=0.3140(44) (FO) and 0.3346 (35) (CI) leading to: αs(MZ)=0.1178(6)fit(3)evol.\alpha_s(M_Z)=0.1178(6)_{fit}(3)_{evol.} (FO) and 0.1202(4)fit(3)evol.0.1202(4)_{fit}(3)_{evol.}(CI). Comparisons with some other results are done.

Keywords

Cite

@article{arxiv.2408.05732,
  title  = {QCD condensates and $\alpha_s$ from $\tau$-decay},
  author = {S. Narison},
  journal= {arXiv preprint arXiv:2408.05732},
  year   = {2025}
}

Comments

Latex file 18 pages, 3 Tables, 14 figures. Version published in Nucl.Phys. A after inclusion of the referee's suggestions

R2 v1 2026-06-28T18:09:45.216Z