Previously published and as yet unpublished QCD results obtained with the ALEPH detector at LEP1 are presented. The unprecedented statistics allows detailed studies of both perturbative and non-perturbative aspects of strong interactions to be carried out using hadronic Z and tau decays. The studies presented include precise determinations of the strong coupling constant, tests of its avour independence, tests of the SU(3) gauge structure of QCD, study of coherence eects, and measurements of single-particle inclusive distributions and two-particle correlations for many identied baryons and mesons.

The polarization of Λ baryons from Z decays is studied with the Aleph apparatus. Evidence of longitudinal polarization of s quarks from Z decay is observed for the first time. The measured longitudinal Λ polarization isPΛL = -0.32 +/- 0.07 for z = p/pbeam > 0.3. This agrees with the prediction of -0.39 +/- 0.08 from the standard model and the constituent quark model, where the error is due to uncertainties in the mechanism for Λ production. The observed Λ polarization is diluted with respect to the primary s quark polarization by Λ baryons without a primary s quark. Measurements of the Λ forward-backward asymmetry and of the correlation between back-to-back ΛΛ pairs are used to check this dilution. In addition the transverse Λ polarization is measured. An indication of transverse polarization, more than two standard deviations away from zero, is found along the normal to the plane defined by the thrust axis and the Λ direction

The Λb polarization in hadronic Z decays is measured in semileptonic decays from the average energies of the charged lepton and the neutrino. In a data sample of approximately 3 million hadronic Z decays collected by the ALEPH detector at LEP between 1991 and 1994, 462 +/- 31 Λb candidates are selected using (Λπ+)-lepton correlations. From this event sample, the Λb polarization is measured to be PΛb = -0.23+0.24-0.20(stat.)+0.08-0.07(syst.)

The reaction e

Earlier measurements at LEP of isolated hard photons in hadronic Z decays, attributed to radiation from primary quark pairs, have been extended in the ALEPH experiment to include hard photon production inside hadron jets. Events are selected where all particles combine democratically to form hadron jets, one of which contains a photon with a fractional energy z 0:7. After statistical subtraction of non-prompt photons, the quark-to-photon fragmentation function, D(z), is extracted directly from the measured 2-jet rate. By taking into account the perturbative contributions to D(z) obtained from an O( S ) QCD calculation, the unknown non-perturbative component o f D ( z ) is then determined at high z. Provided due account is taken of hadronization e ects near z = 1, a good description of the other event topologies is then found.

The inclusive production of D*+/- mesons in photon-photon collisions has been measured by the Aleph experiment at LEP with a beam energy of 45 GeV. The D*+ are detected in their decay to D0π+ with the D0 observed in three separate decay modes: (1) K-π+, (2) K-π+π0 and (3) K-π+π-π+, and analagously for the D*- modes. A total of 33 events was observed from an integrated luminosity of 73 pb-1 which corresponds to a cross section for σ(e+e- -> e+e-D*+/-X) of 155 +/- 33 +/- 21 pb. This result is compatible with both the direct production γγ -> cc in the Born approximation and with a more complete calculation which includes both radiative QCD corrections and contributions in which one of the photons is first resolved into its quark and gluon constituents. The shapes of distributions for events containing a D*+ are found to be better described by the latter

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 Xi(b) is performed with a study of Xi-lepton correlations. Forty-four events with same sign Xi(-)l(-) combinations are found whereas 8.4 are expected based on the rate of opposite sign Xi(-)l(+) combinations. This significant excess is interpreted as evidence for Xi(b) semileptonic decays. The measured product branching ratio is Br(b-->Xi(b))xBr(Xi(b)-->X(c)Xl(-) (nu)over bar (l))xBr(X(c)-->Xi(-)X')=(5.4 +/- 1.1(stat) +/- 0.8(syst))x10(-4) per lepton species, averaged over electrons and muons, with X(c) a charmed baryon. The Xi(b) lifetime is measured to be tau(Xi b)=1.35 + (-0.28)(+0.37)(stat) + (-0.17)(+0.15)(syst) ps

A study of scaling violations in fragmentation functions performed by the ALEPH collaboration at LEP is presented. Data samples enriched in uds, c, b and gluon jets, respectively, together with measurements of the longitudinal and transverse inclusive cross sections are used to extract the fragmentation function for the gluon and for each flavour. The measurements are compared to data from experiments at energies between 22 GeV and 91 GeV and scaling violations consistent with QCD predictions are observed. From this, a measurement of the strong coupling constant αs(Mz) = 0.126 +/- 0.009 is obtained