Abstract
The τ→πππντ decay is driven by the hadronization of the axial-vector current. Within the resonance chiral theory, and considering the large-NC expansion, this process has been studied in Ref. [1] (D. Gómez Dumm, A. Pich, J. Portolés, 2004). In the light of later developments we revise here this previous work by including a new off-shell width for the lightest a1 resonance that provides a good description of the τ→πππντ spectrum and branching ratio. We also consider the role of the ρ(1450) resonance in these observables. Thus we bring in an overall description of the τ→πππντ process in excellent agreement with our present experimental knowledge.
Highlights
The decays of the τ lepton represent an outstanding laboratory for the analysis of various topics in particle physics
Τ decays into hadrons allow to study the hadronization of vector and axial-vector currents, they can be used to determine intrinsic properties of the hadron resonances that govern the dynamics of these processes [1,2,3,4,5,6,7]
Typically E ≪ Mρ [where Mρ is the mass of the ρ(770) meson], chiral perturbation theory [8, 9] is an appropriate effective theory of QCD. In general this approach cannot be extended to the intermediate energy range, in which the dynamics of resonant states plays a major role. This is the case of hadron tau decays: these processes happen to be driven by hadron resonances, and the corresponding energy spectrum extends over a region where these resonances reach their on–shell peaks
Summary
The decays of the τ lepton represent an outstanding laboratory for the analysis of various topics in particle physics. Typically E ≪ Mρ [where Mρ is the mass of the ρ(770) meson], chiral perturbation theory (χPT) [8, 9] is an appropriate effective theory of QCD. In general this approach cannot be extended to the intermediate energy range, in which the dynamics of resonant states plays a major role. [1], where we have analyzed τ → πππντ decays within the resonance chiral theory (RχT) [13,14] This procedure amounts to build an effective Lagrangian in which resonance states are treated as active degrees of freedom. The aim of this work is to reanalyse τ → πππντ processes within the same general scheme, considering the energy-dependent width of the a1 state within a proper RχT framework
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