Confronting generalized hidden local symmetry chiral model with the ALEPH data on the decay tau^- to pi^+ pi^- pi^- nu_tau

TL;DR

This paper tests the GHLS chiral model against ALEPH tau decay data, finds discrepancies with a single resonance, and explores model modifications with additional resonances to better fit the experimental results.

Contribution

It introduces two modifications to the GHLS model with extra axial vector mesons and evaluates their effectiveness in describing tau decay data.

Findings

Single resonance GHLS model disagrees with data.

Adding two heavier axial vector mesons improves data fit.

One modification predicts an unphysically large decay width.

Abstract

Generalized Hidden Local Symmetry (GHLS) model is the chiral model of pseudoscalar, vector, and axial vector mesons and their interactions. It contains also the couplings of strongly interacting particles with electroweak gauge bosons. Here, GHLS model is confronted with the ALEPH data on the decay $\tau^-\to\pi^-\pi^-\pi^+\nu_\tau$. It is shown that the invariant mass spectrum of final pions in this decay calculated in GHLS framework with the single $a_1(1260)$ resonance disagrees with the experimental data at any reasonable number of free GHLS parameters. Two modifications of GHLS model based on inclusion of two additional heavier axial vector mesons are studied. One of them giving a good description of the ALEPH data, with all the parameters kept free is shown to result in very large $\Gamma_{a_1^\pm\to\pi^\pm\gamma}$ partial width. The other scheme with the GHLS parameters fixed in a way that the universality is preserved and the observed central value of $\Gamma_{a_1^\pm\to\pi^\pm\gamma}$ is reached, results in a good description of the three pion spectrum in $\tau^-\to\pi^+\pi^-\pi^-\nu_\tau$ decay.