QCD parameters and SM-high precision from e+e− to Hadrons: Updated
Stephan Narison
所有作者
Stephan Narison
文献摘要
I update my previous comparison of the theoretical value of the muon anomaly with the new measurement and found Δaμ≡aμexp−aμth=(143±42th±22exp)×10−11 which is about 3σ discrepancy between the SM predictions and experiment. 2. I improve the estimate of QCD power corrections up to dimension D=12 and provide a new estimate of the ones up to D=20 within the SVZ expansion by combining the ratio of the Laplace sum rules (LSR) with the BNP τ-like decay moments for the I=1 vector current. The results in Table 1 confirm a violation of the factorization of the four-quark condensates and the value of the gluon one <αsG2> from some other sources. Up to D=20, I there is not any factorial nor exponential growth of the size of these power corrections. 3. I use these new values of power corrections to extract αs from the BNP lowest moment. To order αs4, I find within the SVZ expansion: αs(Mτ)=0.3081(50)fit(71)αs5 [resp. 0.3260(47)fit(62)αs5] implying αs(MZ)=0.1170(6)(3)evol [resp. 0.1192(6)(3)evol] for Fixed Order (FO) [resp. Contour Improved (CI)] PT series. They lead to the mean: αs(Mτ)∣SVZ=0.3179(58)fit(81)syst and αs(MZ)∣SVZ=0.1182(12)(3)evol where the systematic error(syst) takes into account the discrepancy between FO and CI. Using the lowest BNP moment, we also obtain from the vector (V) component of τ-decay the mean: αs(Mτ)∣τ,V=0.3219(52)(91)syst giving: αs(MZ)∣τ,V=0.1187(13)(3)evol. The average of the two determinations leads to: αs(Mτ)=0.3198(72) and αs(MZ)=0.1185(9)(3)evol. 4. Some contributions beyond the SVZ expansion (1/Q2, instantons and duality violation) expected to be small are discussed in Sections 10,11.