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Measurement of the tau lepton lifetime with the three-dimensional impact parameter method

Research output: Contribution to journalJournal article


  • ALEPH Collaboration
<mark>Journal publication date</mark>1997
<mark>Journal</mark>Zeitschrift für Physik C Particles and Fields
Issue number3
Number of pages12
Pages (from-to)387-398
<mark>Original language</mark>English


A new method is presented for the measurement of the mean tau lepton lifetime using events in which tau's are pair-produced and both tau's decay to hadrons and nu(tau). Based on the correlation between the two tau's produced at a symmetric e(+)e(-) collider, the 3DIP method relies on the three-dimensional information from a double-sided vertex detector and on kinematic constraints for the precise measurement of the tau decay angles. Using the data collected from 1992 to 1994 with the ALEPH detector at LEP, a tau lifetime of 288.0 +/- 3.1 +/- 1.3 fs is obtained from the sample in which both tau's decay to one charged track, and 292.8 +/- 5.6 +/- 3.0 fs from the sample in which one tau decays to one prong and the other to three prongs. The results show small statistical correlations with those derived from other methods. When combined with the previously published ALEPH measurements, the resulting tau lifetime is 291.2 +/- 2.0 +/- 1.2 fs.