A Study of Three-Prong Tau Decays with Charged Kaons

TL;DR

This paper measures specific tau decay branching ratios involving charged kaons using OPAL detector data, analyzes the resonant structure, and provides new insights into tau decay modes near the Z0 resonance.

Contribution

It presents the first detailed measurement of three-prong tau decay modes with charged kaons and analyzes the resonant structure assuming dominance of K_1 resonances.

Findings

Branching ratio for tau- -> nu_tau K- pi- pi+ (pi0) is 0.343%

Branching ratio for tau- -> nu_tau K- pi- K+ (pi0) is 0.159%

Ratio of K_1(1270) to total K_1 resonances is 0.71

Abstract

From an analysis of the ionisation energy loss of charged particles selected from a sample of 147926 e+e- -> tau+tau- candidates recorded in the OPAL detector at e+e- centre-of-mass energies near the Z0 resonance, we determine the branching ratios: BR(tau- -> nu_tau K- pi- pi+ (pi0)) = 0.343 +- 0.073 +- 0.031 % BR(tau- -> nu_tau K- pi- K+ (pi0)) = 0.159 +- 0.053 +- 0.020 % where the (pi0) notation refers to decay modes with or without an accompanying pizero. The tau- -> nu_tau K- pi- pi+ (pi0) final states occurring through tau- -> nu_tau K- K_s (pi0) are treated as background in this analysis. We also examine the resonant structure of tau- -> nu_tau K- pi- pi+ candidates. Under the assumption that the resonant structure is dominated by the K_1 resonances, we determine the ratio of the BR (tau- -> K_1(1270)) to the sum of the BRs (tau -> K_1(1270) and (tau -> K_1(1400)) to be 0.71 +- 0.16 +- 0.11. In all results, the first uncertainties are statistical and the second are systematic.