Improved measurement of theB 0 andB + meson lifetimes

The lifetimes of theB0 andB+ mesonshave been measured with theAleph detector at LEP, using approximately 3 million hadronic Z decays collected in the period 1991–1994. In the first of three methods, semileptonic decaysofB0 andB+ mesonswere partially reconstructed by identifying events containing a lepton with an associatedD*− or\(\bar D^0 \) meson. The second method used fully reconstructedB0 andB+ mesons. The third method, used to measure theB0 lifetime, employed a partial reconstruction technique to identifyB0→D*−π+X decays.