The 132 pbt - 1 of data collected by ALEPH from 1991 to 1994 have been used to analyze η and ω production in τ decays. The following branching fractions have been measured: \(B\left( {{\tau ^ - } \to {\nu _\tau }\omega {h^ - }} \right) = \left( {1.91 \pm 0.07 \pm 0.06} \right) \times {10^{ - 2}},\) \(B\left( {{\tau ^ - } \to {\nu _\tau }\omega {h^ - }{\pi ^0}} \right) = \left( {4.3 \pm 0.6 \pm 0.5} \right) \times {10^{ - 3}},\) \(B\left( {{\tau ^ - } \to {\nu _\tau }\eta {K^ - }} \right) = \left( {2.9_{ - 1.2}^{ + 1.3} \pm 0.7} \right) \times {10^{ - 4}},\) \(B\left( {{\tau ^ - } \to {\nu _\tau }\eta {h^ - }{\pi ^0}} \right) = \left( {1.8 \pm 0.4 \pm 0.2} \right) \times {10^{ - 3}}\) and the 95% C.L. limit B(τ− → ντηπt -) < 6.2 × 10t - 4 has been obtained. The ωπt- and ηπt -π0 rates and dynamics are found in agreement with the predictions made from e+e∼ - annihilation data with the help of isospin invariance (CVC).

Two samples of exclusive semileptonic decays, 579 B0 →D∗+ℓ−νℓ events and 261 B0 → D+ℓ−νℓ events, are selected from approximately 3.9 million hadronic Z decays collected by the ALEPH detector at LEP. From the reconstructed differential decay rate of each sample, the product of the hadronic form factor F(ω) at zero recoil of the D(∗)+ meson and the CKM matrix element |Vcb| are measured to be FD∗+(1)|Vcb| = (31.9 ± 1.8stat ± 1.9syst) × 10−3, FD+(1)|Vcb| = (27.8 ± 6.8stat ± 6.5syst) × 10−3. The ratio of the form factors FD+(1) and FD∗+(1) is measured to be FD+(1)FD∗+(1) = 0.87 ± 0.22stat ± 0.21syst. A value of |Vcb| is extracted from the two samples, using theoretical constraints on the slope and curvature of the hadronic form factors and their normalization at zero recoil, with the result |Vcb| = (34.4 ± 1.6stat ± 2.3syst ± 1.4th) × 10−3. The branching fractions are measured from the two integrated spectra to be Br(B0 → D∗+ℓ−νℓ) = (5.53 ± 0.26stat ±0.52syst)%, Br(B0 → D∗+ℓ−νℓ) = (2.35 ± 0.20stat ± 0.44syst)%.

The 132 pb(-1) of data collected by ALEPH from 1991 to 1994 have been used to analyze eta and omega production in 7 decays. The following branching fractions have been measured:B(tau(-) --> nu(tau)omega h(-)) = (1.91 +/- 0.07 +/- 0.06) x 10(-2),B(tau(-) --> nu(tau)omega h(-)pi(0)) = (4.3 +/- 0.6 +/- 0.5) x 10(-3),B(tau(-) --> nu(tau)eta K-) = (2.9(-1.2)(+1.3) +/- 0.7) x 10(-4),B(tau(-) --> nu(tau)eta(h)(-)pi(0)) = (1.8 +/- 0.4 +/- 0.2) x 10(-3)and the 95% C.L. limit B(tau(-) --> nu(tau)eta pi(-)) < 6.2 x 10(-4) has been obtained. The omega pi(-) and eta pi(-)pi(0) rates and dynamics are found in agreement with the predictions made from e(+)e(-) annihilation data with the help of isospin invariance (CVC).

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$$\bar D^0 $$ 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 $$\begin{gathered} \tau _0 = 1.55 \pm 0.06 \pm 0.03 ps, \hfill \\ \tau _ + = 1.58 \pm 0.09 \pm 0.03 ps, \hfill \\ \tfrac{{\tau _ + }}{{\tau _0 }} = 1.03 \pm 0.08 \pm 0.02. \hfill \\ \end{gathered} $$ .

In a data sample of four million hadronic Z decays collected with the ALEPH detector at LEP, four Λb baryon candidates are exclusively reconstructed in the Λb → Λc+π− channel, with the Λc+ decaying into pK−π+, pK0, or Λπ+π+π−. The probability of the observed signal to be due to a background fluctuation is estimated to be 4.2 × 10−4. The mass of the Λb is measured to be 5614±21 (stat.) ± 4 (syst.) MeV/c2.

In a data sample of approximately four million hadronic Z decays recorded with the ALEPH detector from 1990 to 1995, a search for the strange b baryon Ξb is performed with a study of Ξ-lepton correlations. Forty-four events with same sign Ξ−ℓ− combinations are found whereas 8.4 are expected based on the rate of opposite sign Ξ−ℓ+ combinations. This significant excess is interpreted as evidence for Ξb semileptonic decays. The measured product branching ratio is Br(b → Ξb) × Br(Ξb → XcXℓ−νℓ) × Br(Xc → Ξ−X′) = (5.4±1.1(stat) ± 0.8(syst)) × 10−4 per lepton species, averaged over electrons and muons, with Xc a charmed baryon. The Ξb lifetime is measured to be τΞb = 1.35−0.28+0.37(stat)−0.17+0.15(syst) ps.

The inclusive production of charmed particles in Z--> decays has been measured from the yield of D-0, D+, D-s(+) and Lambda(c)(+) decays in a sample of " events with high b purity collected with the ALEPH detector from 1992 to 1995.From these measurements, adding the charmonia production rate and an estimate of the charmed strange baryon contribution, the average number of charm quarks per b decay is determined to be n(c)=1.230+/-0.036+/-0.038+/-0.053, where the uncertainties are due to statistics, systematic effects and branching ratios, respectively."

The electroweak mixing angle is determined with high precision from measurements of the mean difference between forward and backward hemisphere charges in hadronic decays of the Z. A data sample of 2.5 million hadronic Z decays recorded over the period 1990 to 1994 in the ALEPH detector at LEP is used. The mean charge separation between event hemispheres containing the original quark and antiquark is measured for\(b\bar b\) and\(c\bar c\) events in subsamples selected by their long lifetimes or using fastD*’s. The corresponding average charge separation for light quarks is measured in an inclusive sample from the anticorrelation between charges of opposite hemispheres and agrees with predictions of hadronisation models with a precision of 2%. It is shown that differences between light quark charge separations and the measured average can be determined using hadronisation models, with systematic uncertainties constrained by measurements of inclusive production of kaons, protons andΛ’s. The separations are used to measure the electroweak mixing angle precisely as sin2 ϑ w eff =0.2322±0.0008(exp.stat.) ±0.0007(exp.syst.)±0.0008(sep.). The first two errors are due to purely experimental sources whereas the third stems from uncertainties in the quark charge separations.

Quark and gluon jets with the same energy, 24 GeV, are compared in symmetric three-jet configurations from hadronic Z decays observed by the ALEPH detector. Jets are defined using the Durham algorithm. Gluon jets are identified using an anti-tag on b jets, based on a track impact parameter method. The comparison of gluon and mixed flavour quark jets shows that gluon jets have a softer fragmentation function, a larger angular width and a higher particle multiplicity, Evidence is presented which shows that the corresponding differences between gluon and b jets are significantly smaller. In a statistically limited comparison the multiplicity in c jets was found to be comparable with that observed for the jets of mixed quark flavour.

Four candidates for charmless hadronic B decay are observed in a data sample of four million hadronic Z decays recorded by the aleph detector at lep. The probability that these events come from background sources is estimated to be less than 10−6. The average branching ratio of weakly decaying B hadrons (a mixture of Bd0, Bs0 and Λb weighted by their production cross sections and lifetimes, here denoted B) into two long-lived charged hadrons (pions, kaons or protons) is measured to be Br(B → h+h−) = (1.7−0.7+1.0 ± 0.2) × 10−5. The relative branching fraction Br(Bd(s)0 → π+π−(K−))Br(Bd(s)0 → h+h−) is measured to be 1.0−0.3 −0.1+0.0 +0.0. In addition, branching ratio upper limits are obtained for a variety of exclusive charmless hadronic two-body decays of B hadrons.

A lower limit on the oscillation frequency of the B0 SB0 S system is obtained from approximately four million hadronic Z decays accumulated using the ALEPH detector at LEP from 1991 to 1995. Leptons are combined with opposite sign D- S candidates reconstructed in seven different decay modes as evidence of semileptonic B0 S decays. Criteria designed to ensure precise proper time reconstruction select 277 D- Sl+ combinations. The initial state of these B0 S candidates is determined using an algorithm optimized to efficiently utilise the tagging information available for each event. The limit at 95% confidence level on the B0 SB0 S oscillation frequency is ��ms > 6.6 ps-1. The same data is used to update the measurement of the B0 S lifetime, ��s = 1.54 +0.14 -0.13, (stat) �� 0.04 (syst) ps.

The B-0-B-0 average mixing parameter <(chi)over bar> and b forward-backward asymmetry A(FB)(0)(b) are measured from a sample of about 4200000 Z-->" events recorded with the ALEPH detector at LEP in the years 1990-1995. High transverse momentum electrons and muons produced in b semileptonic decays provide the tag of the quark flavour and of its charge.The average mixing parameter and the pole b asymmetry are measured to be <(chi)over bar>=0.1246+/-0.0051(stat)+/-0.0052(syst), A(FB)(0)(b)=0.1008+/-0.0043(stat)+/-0.0028(syst). The value of sin(2) theta(W)(eff)=0.23198+/-0.00092 is extracted from the asymmetry measurement."

The reaction e+e− → HZ∗ is used to search for the standard model Higgs boson in the Hνν and the Hℓ+ℓ− channels. The data sample corresponds to about 4.5 million hadronic Z decays collected by the ALEPH experiment at LEP from 1989 to 1995 at centre-of-mass energies at and around the Z peak. Three candidate events are found in the Hμ+μ− channel, in agreement with the expected background from the electroweak process e+e− ℓ+ℓ−qq. This search results in a 95% C.L. lower limit on the Higgs boson mass of 63.9 GeV/c2.

A lower limit on the oscillation frequency of the Bs0Bs0 system is obtained from approximately four million hadronic Z decays accumulated using the ALEPH detector at LEP from 1991 to 1995. Leptons are combined with opposite sign Ds− candidates reconstructed in seven different decay modes as evidence of semileptonic Bs0 decays. Criteria designed to ensure precise proper time reconstruction select 277Ds−ℓ+ combinations. The initial state of these Bs0 candidates is determined using an algorithm optimized to efficiently utilise the tagging information available for each event. The limit at 95% confidence level on the Bs0Bs0 oscillation frequency is Δms > 6.6 ps−1. The same data is used to update the measurement of the Bs0 lifetime,τs = 1.54−0.13+0.14 (stat) ± 0.04 (syst) ps.

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! $$\begin{gathered} \tau _0 = 1.55 \pm 0.06 \pm 0.03 ps, \hfill \\ \tau _ + = 1.58 \pm 0.09 \pm 0.03 ps, \hfill \\ \tfrac{{\tau _ + }}{{\tau _0 }} = 1.03 \pm 0.08 \pm 0.02. \hfill \\ \end{gathered} $$ .

About three million hadronic decays of the Z collected by ALEPH in the years 1991 to 1994 are used to search for anomalous CP violation beyond the Standard Model in the decay Z → bbg. The study is performed by analyzing angular correlations between the two quarks and the gluon in three-jet events and by measuring the differential two-jet rate. No signal of CP violation is found. For the combinations of anomalous CP violating couplings, ĥb = ĥAbgVb − ĥVbgAb and b∗ = ĥVb2+ĥAb2, limits of | ĥb | < 0.59 and hb∗ < 3.02 are given at 95% CL.

Data collected by ALEPH in the years 1990, 1991 and 1992 have been used to update a previous search for CP violation in the decay of the Z into tau(+)tau(-). The measurement of the weak dipole form factor of the tau lepton has been performed by studying correlations between the tau leptons. No signal of CP violation was found. The weak dipole form factor is found to be ($) over tilde d(tau) = (+0.15 +/- 0.58(stat) +/- 0.38(sys)) 10(-17)e . cm, obtained with 19628 identified tau(+)tau(-) events. This gives an upper limit on the weak dipole form factor of j\($) over tilde d(tau)\ < 1.5 . 10(-17)e . cm at the 95% confidence level.

The lifetime of the Bs0 meson is measured in approximately 3 million hadronic Z decays accumulated using the ALEPH detector at LEP from 1991 to 1994. Seven different Ds− decay modes were reconstructed and combined with an opposite sign lepton as evidence of semileptonic Bs0 decays. Two hundred and eight Ds−ℓ+ candidates satisfy selection criteria designed to ensure precise proper time reconstruction and yield a measured Bs0 lifetime of τ(Bs0) = 1.59−0.15+0.17 (stat) ±0.03 (syst) ps. Using a larger, less constrained sample of events, the product branching ratio is measured to be Br(b→Bs0) ·Br(Bs0→Ds−ℓ+νX) = 0.82 ± 0.09 (stat) −0.14+0.13 (syst) %.