Improved measurement of the $B^0$ and $B^+$ meson lifetimes

Abstract

The lifetimes of theB 0 andB + mesons have 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 decays ofB 0 andB + mesons were partially reconstructed by identifying events containing a lepton with an associatedD*− or % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGabmirayaara% WaaWbaaSqabeaacaaIWaaaaaaa!37B5! $$\bar D^0 $$ meson. The second method used fully reconstructedB 0 andB + mesons. The third method, used to measure theB 0 lifetime, employed a partial reconstruction technique to identifyB 0→D*− π + X decays. The combined results are % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGceaqabeaacqaHep% aDdaWgaaWcbaacbaGaa8hmaaqabaGccqGH9aqpcaaIXaGaaiOlaiaa% iwdacaaI1aGaeyySaeRaaGimaiaac6cacaaIWaGaaGOnaiabgglaXk% aaicdacaGGUaGaaGimaiaaiodaruqqYLwySbacfaGaa4hiaiaa-bha% caWFZbGaaiilaaqaaiabes8a0naaBaaaleaacaWFRaaabeaakiabg2% da9iaaigdacaGGUaGaaGynaiaaiIdacqGHXcqScaaIWaGaaiOlaiaa% icdacaaI5aGaeyySaeRaaGimaiaac6cacaaIWaGaaG4maiaa+bcaca% WFWbGaa83CaiaacYcaaeaadaWcbaWcbaGaeqiXdq3aaSbaaWqaaiaa% -TcaaeqaaaWcbaGaeqiXdq3aaSbaaWqaaiaa-bdaaeqaaaaakiabg2% da9iaaigdacaGGUaGaaGimaiaaiodacqGHXcqScaaIWaGaaiOlaiaa% icdacaaI4aGaeyySaeRaaGimaiaac6cacaaIWaGaaGOmaiaac6caaa% aa!72AD! $$\begin{gathered} \tau _0 = 1.55 \pm 0.06 \pm 0.03 ps, \hfill \\ \tau _ + = 1.58 \pm 0.09 \pm 0.03 ps, \hfill \\ \tfrac{{\tau _ + }}{{\tau _0 }} = 1.03 \pm 0.08 \pm 0.02. \hfill \\ \end{gathered} $$ .