Regular Article - Experimental Physics
A global treatment of VMD physics up to the φ: II. τ decay and hadronic contributions to g−2
LPNHE Paris VI/VII, IN2P3/CNRS, 75252, Paris, France
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Revised: 18 June 2010
Published online: 14 July 2010
Relying on the Hidden Local Symmetry (HLS) model equipped with a mechanism breaking the U(3)/SU(3)/SU(2) symmetries and generating a dynamical vector meson mixing, it has been shown that a global fit successfully describes the cross sections for the e + e −→π + π −, e + e −→(π 0/η)γ and e + e −→π 0 π + π − annihilation channels. One extends this global fit in order to include also the dipion spectra from the τ decay, taking into account all reported information on their statistical and systematic errors. A model accounting for lineshape distortions of the ρ ± spectrum relative to ρ 0 is also examined when analyzing the τ data behavior within the global fit framework. One shows that a successful account for e + e − annihilation data and τ spectra can be simultaneously reached. Then, issues related with non-perturbative hadronic contributions to the muon g−2 are examined in details. It is shown that all e + e − data considered together allow for improved and motivated estimates for the a μ (π + π −), the π + π − loop contribution to the muon g−2; for instance, integrated between 0.630 and 0.958 GeV, we find a μ (π + π −)=359.62±1.62 (in units of 10−10), a 40% improvement of the current uncertainty. The effects of the various τ samples in the context of a global fit procedure leads to conclude that different lineshape distortions are revealed by the ALEPH, BELLE and CLEO data samples. Relying on global fits to the data quoted above, one also provides motivated estimates of the π + π −, π 0 γ, η γ and π 0 π + π − contributions to a μ up to 1 GeV with the smallest possible uncertainties. These estimates are based on various global fit configurations, each yielding a good probability.
© Springer-Verlag / Società Italiana di Fisica, 2010