Leptonic decays of the D(s) meson
The purely leptonic decays Ds→τν and Ds→μν are studied in a sample of four million hadronic Z decays collected with the ALEPH detector at the LEP e+e− collider from 1991 to 1995. The branching fractions are extracted from a combination of two analyses, one optimized to select Ds→τν decays with or , and the other optimized for Ds→μν decays. The results are used to evaluate the Ds decay constant, within the Standard Model: fDs=[285±19(stat)±40(syst)] MeV.

title: Study of the subjet structure of quark and gluon jets
abstract: Measurements of the subjet structure of quark and gluon jets in hadronic Z decays are presented. The analysis is based on one million hadronic events recorded by the Aleph detector. Roughly symmetric three-jet events are selected with a coarse jet-resolution cut-off, y1. Gluon jets are identified with a purity of 94.6% in those events where evidence of long-lived heavy-flavour hadrons in the other two jets is found. The jets are then analyzed using a smaller cut-off y0 (< y1) so that subjets are resolved. The properties of the jets (subjet multiplicities (Nq), (Ng) and rates Rng(q) for n = 1, 2, 3, 4) are determined and are found to be in good agreement with the expectations of perturbative QCD as long as the subjet resolution parameter y0 is sufficiently large to keep non-perturbative effects small. In particular, the ratio , which to leading order in QCD is given by the ratio of colour factors , is measured to be 1.96 ± 0.15 for y0 = 2 · 10−3, but falls to 1.29 ± 0.03 for y0 = 1.6 · 10−5.

title: A precise determination of the number of families with light neutrinos and of the Z boson partial widths
abstract: More extensive and precise results are reported on the parameters of Z decay. On the basis of 20 000 Z decays collected with the ALEPH detector at LEP we find Mz=91.182±0.026 (exp.) ±0.030 (beam) GeV, Γz=2.541±0.056 GeV and σhad0=41.4±0.8 nb. The partial widths for the hadronic and leptonic channels are Γhad=1804±44 MeV, Γe+e−=82.1±3.4 MeV, Γμ+μ−=87.9±6.0 MeV and Γτ+τ−=86.1±5.6 MeV, in good agreement with the standard model. On the basis of the average leptonic width Γl+l−=83.9±2.2 MeV, the effective weak mixing angle is found to be sin2θw(Mz)=0.231±0.008. Usin g the partial widths calculated in the standard model, the number of light neutrino families is Nν=3.01±0.15 (exp.)±0.05 (theor.).

title: Charm counting in b decays
abstract: The inclusive production of charmed particles in decays has been measured from the yield of D0, D+, Ds+ and Λc+ 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 nc = 1.230 ± 0.036 ± 0.038 ± 0.053, where the uncertainties are due to statistics, systematic effects and branching ratios, respectively.

title: Measurement of the W mass in $e^+e^-$ collisions at production threshold
abstract: In June 1996, the LEP centre-of-mass energy was raised to 161 GeV. Pair production of W bosons in e+e− collisions was observed for the first time by the LEP experiments. An integrated luminosity of 11 pb−1 was recorded in the ALEPH detector, in which WW candidate events were observed. In 6 events both Ws decay leptonically. In 16 events, one W decays leptonically, the other into hadrons. In the channel where both Ws decay into hadrons, a signal was separated from the large background by means of several multi-variate analyses. The W pair cross-section is measured to be σWW = 4.23 ± 0.73 (stat.) ± 0.19 (syst.) pb. From this cross-section, the W mass is derived within the framework of the Standard Model: mW = 80.14 ± 0.34 (stat.) ± 0.09 (syst.) ± 0.03 (LEP energy) GeV/c2

title: Measurement of the tau lepton lifetime
abstract: The mean lifetime of the lepton is measured in a sample of 25700 pairs collected in 1992 with the ALEPH detector at LEP. A new analysis of the 1-1 topology events is introduced. In this analysis, the dependence of the impact parameter sum distribution on the daughter track momenta is taken into account, yielding improved precision compared to other impact parameter sum methods. Three other analyses of the oneand three-prong decays are updated with increased statistics. The measured lifetime is 293:5 3:1 1:7 fs. Including previous (1989{1991) ALEPH measurements, the combined lifetime is 293:7 2:7 1:6 fs.

title: Toward an understanding of thermal X-ray emission of pulsars
abstract: We present a theoretical model for the thermal X-ray emission and cooling of isolated pulsars, assuming that pulsars are solid quark stars. We calculate the heat capacity for such a quark star, and the results show that the residual thermal energy cannot sustain the observed thermal X-ray luminosities seen in typical isolated X-ray pulsars. We conclude that other heating mechanisms must be in operation if the pulsars are in fact solid quark stars. Two possible heating mechanisms are explored. Firstly, for pulsars with little magnetospheric activities, accretion from the interstellar medium or from the material in the associated supernova remnants may power the observed thermal emission. In the propeller regime, a disk-accretion rate ${\dot M}\sim$1% of the Eddington rate with an accretion onto the stellar surface at a rate of $\sim 0.1% {\dot M}$ could explain the observed emission luminosities of the dim isolated neutron stars and the central compact objects. Secondly, for pulsars with significant magnetospheric activities, the pulsar spindown luminosities may have been as the sources of the thermal energy via reversing plasma current flows. A phenomenological study between pulsar bolometric X-ray luminosities and the spin energy loss rates presents the probable existence of a 1/2-law or a linear law, i.e. $L_{\rm bol}^{\infty}\propto\dot{E}^{1/2}$ or $L_{\rm bol}^{\infty}\propto\dot{E}$. This result together with the thermal properties of solid quark stars allow us to calculate the thermal evolution of such stars. Thermal evolution curves, or cooling curves, are calculated and compared with the `temperature-age' data obtained from 17 active X-ray pulsars. It is shown that the bolometric X-ray observations of these sources are consistent with the solid quark star pulsar model.

title: Nature and Nurture: a Model for Soft Gamma-Ray Repeaters
abstract: During supernova explosions, strange stars with almost bare quark surfaces may be formed. Under certain conditions, these stars could be rapidly spun down by the torque exerted by the fossil disks formed from the fallback materials. They may also receive large kicks and hence have large proper-motion velocities. When these strange stars pass through the spherical "Oort" comet cloud formed during the presupernova era, they will capture some small-scale comet clouds and collide with some comet-like objects occasionally. These impacts can account for the repeating bursts as observed from the soft gamma repeaters. According to this picture, it is expected that SGR 1900+14 will become active again during 2004-2005.

title: Recent developments of inverse Compton scattering model of pulsar radio emission
abstract: Many theoretical efforts were made to understand the core and conal emission identified from observations by Rankin (1983) and Lyne and Manchester (1988). One of them, named as inverse Compton scattering (ICS) model (Qiao & Lin 1998), has been proposed. It is found in the model that: there are central or `core' emission beam, and one or two hollow conical emission beams; the different emission components are emitted at different heights; owing to different radiation components emitted from different height, the observed emission beams can be shifted from each other due to retardation and aberration effects; the sizes of emission components change with frequencies. Recent developments of the model include: simulations of pulse profiles at different frequencies; studying the basic polarization properties of inverse Compton scattering in strong magnetic fields; computing the polarizations and spectrum of core and cones. A new classification system was also proposed. The main results calculated from the model are consistent with the observations.

title: On the Inverse Compton Scattering Model of Radio Pulsars
abstract: Some characteristics of the inverse Compton scattering (ICS) model are reviewed. At least the following properties of radio pulsars can be reproduced in the model: core or central emission beam, one or two hollow emission cones, different emission heights of these components, diverse pulse profiles at various frequencies, linear and circular polarization features of core and cones.

title: Measurement of the inclusive decay properties of charmed mesons
abstract: We report a high statistics study of the inclusive decay properties of the charmed D 0 and D + mesons, and the first inclusive study of the charmed D s + . The data are collected at s =3.77 GeV and s =4.14 GeV with the Mark III detector at the e + e − storage ring SPEAR. For each charmed meson species, the charged-particle multiplicity, the strangeness content of the final state, and the average π 0 multiplicity are determined.