Search for charginos nearly mass degenerate with the lightest neutralino in e(+)e(-) collisions at centre-of-mass energies up to 209 GeV
A search for charginos nearly mass degenerate with the lightest neutralino is performed with the data collected by the ALEPH detector at LEP, at centre-of-mass energies between 189 and 209 GeV, corresponding to an integrated luminosity of 628 pb(-1). The analysis is based on the detection of isolated and energetic initial state radiation photons, produced in association with chargino pairs whose decay products have little visible energy. The number of candidate events observed is in agreement with that expected from Standard Model background sources. These results are combined with those of other direct searches for charginos, and a lower limit of 88 GeV/c(2) at 95% confidence level is derived for the chargino mass in the case of heavy sfermions, irrespective of the chargino-neutralino mass difference.

title: Production of D**s mesons in hadronic Z decays
abstract: The production rates of the orbitally excited Ds** mesons, Ds1 and Ds2*, are measured with the 4.1 million hadronic Z decays recorded by the ALEPH detector during 1991--1995. The Ds** mesons are reconstructed in the decay modes Ds1+ -> D*+ K0, Ds1+ -> D*0 K+ and Ds2*+ -> D0 K+. The production rate of the Ds1 is measured to be n(Z->Ds1+-)=(0.52+-0.09+-0.06)%, under the assumption that the two considered decay modes of the Ds1 saturate the branching ratio. The production rate of the Ds2* is determined to be n(Z->Ds2*+-)=(0.83+-0.29+0.07-0.13)%, assuming that the branching fraction of the decay Ds2*+ -> D0 K+ is 45%. The production rates in Z->cc and Z->bbar decays are measured separately.

title: Measurement of W pair production in e+ e- collisions at 183-GeV
abstract: The production of W + W − pairs is analysed in a data sample collected by ALEPH at a mean centre-of-mass energy of 182.7 GeV, corresponding to an integrated luminosity of 57 pb −1 . Cross sections are given for different topologies of W decays into leptons or hadrons. Under Standard Model assumptions for the W-pair production and decay, the W-pair cross section is measured to be 15.57±0.62 (stat.) ±0.29 (syst.) pb . Using also the W-pair data samples collected by ALEPH at lower centre-of-mass energies, the decay branching ratio of the W boson into hadrons is measured to be B(W→hadrons) =68.93±1.21 (stat.) ±0.51 (syst.) % , allowing a determination of the CKM matrix element |V cs |=1.043±0.058 (stat.) ±0.026 (syst.) . The agreement of the cross sections with the Standard Model prediction allows a limit to be set on the W decay rate to undetectable final states.

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: 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: 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: He star evolutionary channel to intermediate-mass binary pulsar PSR J1802-2124
abstract: The intermediate-mass binary pulsars (IMBPs) are characterized by relatively long spin periods (10 - 200 ms) and massive ($\ga 0.4 M_{\odot}$) white dwarf (WD) companions. Recently, precise mass measurements have been performed for the pulsar and the WD in the IMBP PSR J1802-2124. Some observed properties, such as the low mass of the pulsar, the high mass of the WD, the moderately long spin period, and the tight orbit, imply that this system has undergone a peculiar formation mechanism. In this work, we attempt to simulate the detailed evolutionary history of PSR J1802-2124. We propose that a binary system consisting of a neutron star (NS, of mass $1.3 M_{\odot}$) and an He star (of mass $1.0 M_{\odot}$), and with an initial orbital period of 0.5 d, may have been the progenitor of PSR J1802-2124. Once the He star overflows its Roche lobe, He-rich material is transferred onto the NS at a relatively high rate of $\sim 10^{-7}-10^{-6} M_{\odot}\,\rm yr^{-1}$, which is significantly higher than the Eddington accretion rate. A large amount of the transferred material is ejected from the vicinity of the NS by radiation pressure and results in the birth of a mildly recycled pulsar. Our simulated results are consistent with the observed parameters of PSR J1802-2124. Therefore, we argue that the NS + He star evolutionary channel may be responsible for the formation of most IMBPs with orbital periods $\la 3 \rm d$.

title: SWIFT J1749.4−2807: A neutron or quark star?
abstract: We investigate a unique accreting millisecond pulsar with X-ray eclipses, SWIFT J1749.4-2807 , and try to set limits on the binary system by various methods including use of the Roche lobe, the mass-radius relations of both main sequence (MS) and white dwarf (WD) companion stars, as well as the measured mass function of the pulsar. The calculations are based on the assumption that the radius of the companion star has reached its Roche radius (or is at 90%), but the pulsar's mass has not been assumed to be a certain value. Our results are as follows. The companion star should be an MS one. For the case that the radius equals its Roche one, we have a companion star with mass M ≃ 0.51 M ⊙ and radius R c ≃ 0.52 R ⊙ , and the inclination angle is i ≃ 76.5° ; for the case that the radius reaches 90% of its Roche one, we have M ≃ 0.43 M ⊙ , R c ≃ 0.44 R ⊙ and i ≃ 75.7° . We also obtain the mass of J1749, M p ≃ 1 M ⊙ , and conclude that the pulsar could be a quark star if the ratio of the critical frequency of rotation-mode instability to the Keplerian one is higher than ∼ 0.3. The relatively low pulsar mass (about ∼ M ⊙ ) may also challenge the conventional recycling scenario for the origin and evolution of millisecond pulsars. The results presented in this paper are expected to be tested by future observations.

title: To Constrain the Parameter Space of the ICS Model
abstract: The pulse profile of pulsar gives geometric information about pulsar's radiation model. After investigating the pulse profiles of PSR B1642-03 and PSR B0950+08, we calculate the ratios of beam width and the emission height between different frequencies. We find that the ratios are almost constants as inclination angle $\alpha$ changes from $0^{\circ}$ to $90^{\circ}$. The ratios can be used to test pulsar's radiation model. In particular it can well constrain the parameter space of the inverse Compton scattering (ICS) model. These constrained parameters indicate some physical implication for the ICS model.

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: Vibration-Powered Radiation of Quaking Magnetar
abstract: In juxtaposition with the standard model of rotation-powered pulsar, the model of vibration-powered magnetar undergoing quake-induced torsional Alfven vibrations in its own ultrastrong magnetic field experiencing decay is considered. The presented line of argument suggests that the gradual decrease of frequencies (lengthening of periods) of long-periodic-pulsed radiation detected from a set of X-ray sources can be attributed to magnetic-field-decay-induced energy conversion from seismic vibrations to magnetodipole radiation of quaking magnetar.