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Study of tau decays involving kaons, spectral functions and determination of the strange quark mass

Research output: Contribution to journalJournal article

Published

Journal publication date12/1999
JournalThe European Physical Journal C (EPJ C) - Particles and Fields
Journal number4
Volume11
Number of pages20
Pages599-618
Original languageEnglish

Abstract

All ALEPH measurements of branching ratios of τ decays involving kaons are summarized including a combination of results obtained with K0S and K0L 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 KK¯¯¯π 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 τ decay into all strange final states is determined to be B(τ−→X−(S=−1)ντ)=(28.7±1.2)×10−3 . The measured mass spectra of the strange τ 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 ms(M2τ)=(176+46−57) MeV/ c2 . The evolution down to 1 GeV gives ms(1GeV2)=(234+61−76)MeV/c2 .