Tau hadronic branching ratios

The European Physical Journal C, 1998

The branching ratios of the τ − → h − ν τ , τ − → h − π 0 ν τ and τ − → h − ≥ 2π 0 ν τ decays have been measured using the 1991-1995 data recorded with the OPAL detector at LEP. These branching ratios are measured simultaneously using three selection criteria and are found to be BR(τ − → h − ν τ) = (1 1. 98 ± 0.13 ± 0.16) % BR(τ − → h − π 0 ν τ) = (25.89 ± 0.17 ± 0.29) % BR(τ − → h − ≥ 2π 0 ν τ) = (9.91 ± 0.31 ± 0.27) % where the first error is statistical and the second is systematic.

2015

CERN-LEP. An analysis based on 124000 selected $\tau$ pairs recorded by the ALEPH detector at LEP provides the vector ($V$) and axial-vector ($A$) spectral functions of hadronic $\tau$ decays together with their total widths. This allows the evaluation of finite energy chiral sum rules that are weighted integrals over the $(V-A)$ spectral functions. In addition, a precise measurement of $\alpha_s$ along with a determination of non-perturbative contributions at the $\tau$ mass scale is performed. The experimentally and theoretically most robust determination of $\alpha_s(M_\tau^2)$ is obtained from the $(V+A)$ fit that yields $\alpha_s(M_\tau^2) = 0.334 \pm 0.022$ giving $\alpha_s(M_Z^2) = 0.1202 \pm 0.0027$ after the extrapolation to the mass of the Z boson. The approach of the Operator Product Expansion (OPE) is tested experimentally studying the evolution of the hadronic widths to masses smaller than the $\tau$ mass. These numbers have been read from the plots in the paper.

The European Physical Journal C, 2016

This paper presents a new method of reconstructing the individual charged and neutral hadrons in tau decays with the ATLAS detector. The reconstructed hadrons are used to classify the decay mode and to calculate the visible four-momentum of reconstructed tau candidates, significantly improving the resolution with respect to the calibration in the existing tau reconstruction. The performance of the reconstruction algorithm is optimised and evaluated using simulation and validated using samples of Z → ττ and Z(→ µµ)+jets events selected from proton-proton collisions at a centre-of-mass energy √ s = 8 TeV, corresponding to an integrated luminosity of 5 fb −1 .