Study of ${\tau}$ decays involving kaons, spectral functions and determination of the strange quark mass

The ALEPH Collaboration: R. Barate - et al.

doi:doi:10.1007/s100520050659

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2019 Impact factor 4.389

Particles and Fields

Eur. Phys. J. C 11, 599-618
DOI 10.1007/s100529900208

Study of ${\tau}$ decays involving kaons, spectral functions and determination of the strange quark mass

The ALEPH Collaboration

R. Barate - et al.

Laboratoire de Physique des Particules (LAPP), IN²P³-CNRS, 74019 Annecy-le-Vieux Cedex, France

Received: 24 February 1999 / Published online: 14 October 1999

Abstract
All ALEPH measurements of branching ratios of ${\tau}$ decays involving kaons are summarized including a combination of results obtained with K⁰_S and K⁰_L detection. The decay dynamics are studied, leading to the determination of contributions from vector K^*(892) and K^*(1410), and axial-vector K₁(1270) and K₁(1400) resonances. Agreement with isospin symmetry is observed among the different final states. Under the hypothesis of the conserved vector current, the spectral function for the $K\overline{K}\pi$ mode is compared with the corresponding cross section for low energy e⁺e^- annihilation, yielding an axial-vector fraction of $(94^{\,+6}_{\,-8})\%$ for this mode. The branching ratio for ${\tau}$ decay into all strange final states is determined to be $B(\tau^-\to X^-(S=-1)\nu_\tau)=(28.7\pm1.2)\times 10^{-3}$ . The measured mass spectra of the strange ${\tau}$ decay modes are exploited to derive the S=-1 spectral function. A combination of strange and nonstrange spectral functions is used to determine the strange quark mass and nonperturbative contributions to the strange hadronic width. A method is developed to avoid the bad convergence of the spin zero hadronic component, with the result $m_s(M_\tau^2)=(176^{\,+46}_{\,-57})$ MeV/c². The evolution down to 1 GeV gives $m_s(1~{\rm GeV}^2) = (234^{\,+61}_{\,-76})~{\rm MeV}/c^2$ .