R value measurements for e+e− annihilation at 2.60, 3.07 and 3.65 GeV
TL;DR: In this paper, the cross sections for e + e − annihilation into hadronic final states (R values) were measured with statistical errors that were smaller than 1%, and systematic errors that are about 3.5 %.
About: This article is published in Physics Letters B.The article was published on 2009-06-29 and is currently open access. It has received 74 citations till now. The article focuses on the topics: Electron–positron annihilation.
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TL;DR: Recently, the LHCb Collaboration discovered two hidden-charm pentaquark states, which are also beyond the quark model as discussed by the authors, and investigated various theoretical interpretations of these candidates of the multiquark states.
1,083 citations
TL;DR: The current status of the Standard Model calculation of the anomalous magnetic moment of the muon is reviewed in this paper, where the authors present a detailed account of recent efforts to improve the calculation of these two contributions with either a data-driven, dispersive approach, or a first-principle, lattice approach.
801 citations
TL;DR: In this paper, the authors reevaluate the hadronic contributions to the muon magnetic anomaly, and to the running of the electromagnetic coupling constant at the Z-boson mass, and find that the reduced electromagnetic coupling strength at M ✓ Z ≥ 2 leads to an increase by 12 ǫ in the central value of the Higgs boson mass obtained by the standard Gfitter fit to electroweak precision data.
Abstract: We reevaluate the hadronic contributions to the muon magnetic anomaly, and to the running of the electromagnetic coupling constant at the Z-boson mass. We include new π
+
π
− cross-section data from KLOE, all available multi-hadron data from BABAR, a reestimation of missing low-energy contributions using results on cross sections and process dynamics from BABAR, a reevaluation of all experimental contributions using the software package HVPTools together with a reanalysis of inter-experiment and inter-channel correlations, and a reevaluation of the continuum contributions from perturbative QCD at four loops. These improvements lead to a decrease in the hadronic contributions with respect to earlier evaluations. For the muon g−2 we find lowest-order hadronic contributions of (692.3±4.2)⋅10−10 and (701.5±4.7)⋅10−10 for the e
+
e
−-based and τ-based analyses, respectively, and full Standard Model predictions that differ by 3.6σ and 2.4σ from the experimental value. For the e
+
e
−-based five-quark hadronic contribution to $\alpha(M_{Z}^{2})$
we find $\varDelta \alpha_{\mathrm{had}}^{(5)}(M_{Z}^{2}) =(274.9\pm1.0)\cdot10^{-4}$
. The reduced electromagnetic coupling strength at M
Z
leads to an increase by 12 GeV in the central value of the Higgs boson mass obtained by the standard Gfitter fit to electroweak precision data.
794 citations
TL;DR: In this paper, the authors evaluated the hadronic vacuum polarisation contributions to the muon magnetic anomaly and to the running of the electromagnetic coupling constant at the Z-boson mass.
Abstract: We reevaluate the hadronic vacuum polarisation contributions to the muon magnetic anomaly and to the running of the electromagnetic coupling constant at the Z-boson mass. We include newest $e^+e^- \rightarrow \mathrm{hadrons}$ cross-section data (among others) from the BABAR and VEPP-2000 experiments. For the muon $(g-2)/2$ we find for the lowest-order hadronic contribution $(693.1 \pm 3.4)\times 10^{-10}$ , improving the precision of our previous evaluation by 21%. The full Standard Model prediction differs by $3.5\,\sigma $ from the experimental value. The five-quark hadronic contribution to $\alpha (m_Z^2)$ is evaluated to be $(276.0\pm 0.9)\times 10^{-4}$ .
512 citations
TL;DR: In this paper, the authors presented a complete reevaluation of the hadronic vacuum polarization contributions to the anomalous magnetic moment of the muon, aμhad,VP, and Δαhad(MZ2), from the combination of e+e-→hadrons cross section data.
Abstract: This work presents a complete reevaluation of the hadronic vacuum polarization contributions to the anomalous magnetic moment of the muon, aμhad,VP, and the hadronic contributions to the effective QED coupling at the mass of the Z boson, Δαhad(MZ2), from the combination of e+e-→hadrons cross section data. Focus has been placed on the development of a new data combination method, which fully incorporates all correlated statistical and systematic uncertainties in a bias free approach. All available e+e-→hadrons cross section data have been analyzed and included, where the new data compilation has yielded the full hadronic R-ratio and its covariance matrix in the energy range mπ≤s≤11.2 GeV. Using these combined data and perturbative QCD above that range results in estimates of the hadronic vacuum polarization contributions to g-2 of the muon of aμhad,LO VP=(693.26±2.46)×10-10 and aμhad,NLO VP=(-9.82±0.04)×10-10. The new estimate for the Standard Model prediction is found to be aμSM=(11659182.04±3.56)×10-10, which is 3.7σ below the current experimental measurement. The prediction for the five-flavor hadronic contribution to the QED coupling at the Z boson mass is Δαhad(5)(MZ2)=(276.11±1.11)×10-4, resulting in α-1(MZ2)=128.946±0.015. Detailed comparisons with results from similar related works are given.
493 citations
References
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TL;DR: This work designs and implements a parser replacement for the FORTRAN 77 programming language, and demonstrates the power of the JETSET programming language.
972 citations
889 citations
TL;DR: In this article, the formulae are collected which are needed for the computation of the strong coupling constant and quark masses at different energy scales and for different number of active flavors.
639 citations
TL;DR: In this article, the authors presented the results of the total analytical reevaluation of the massless next-next-to-leading αs3 QCD correction to R(s) = σtot(e+e−→γ→hadrons)/σ(e−e −→μ+μ−).
464 citations