Measurement of the average lifetime of b hadrons

The average lifetime ofB hadrons has been measured by the TASSO collaboration using 110 pb−1 of data collected in 1986 at a center of mass energy of 35 GeV. Measurements by three different methods are presented and a method ofB-enrichment is discussed. The result of the impact parameter method is τB=1.36±0.13±0.28 ps, that of the vertex method is τB=1.30±0.10±0.28 ps and that of the dipole method is τB=1.47±0.14±0.30 ps. These are combined to give the result τB=1.35±0.10±0.24 ps.