Measurement of the W mass in e+e−e^+ e^- collisions at 183 GeV

The mass of the W boson is obtained from reconstructed invariant mass distributions in W-pair events. The sample of W pairs is selected from 57 pb$^{-1}$ collected with the ALEPH detector in 1997 at a centre-of-mass energy of 183 GeV. The invariant mass distributions of reweighted Monte Carlo events are fitted separately to the experimental distributions in the $qqbarqqbar$ and all l\nuqqbar channels to give the following W masses: $m_{W}^{hadronic} = 80.461 \pm 0.177(stat.) \pm 0.045(syst.) \pm 0.056(theory) GeV/c^2$, $m_{W}^{semileptonic} = 80.326 \pm 0.184(stat.) \pm 0.040(syst.) GeV/c^2$ where the theory error represents the possible effects of final state interactions. The combination of these two measurements, including the LEP energy calibration uncertainty, gives $m_{W} = 80.393 \pm 0.128(stat.)\pm 0.041(syst.) \pm 0.028(theory)\pm 0.021(LEP) GeV/c^2

Measurement of the W mass in e+ e- collisions at 183-GeV

The mass of the W boson is obtained from reconstructed invariant mass distributions in W-pair events. The sample of W pairs is selected from 57 pb-1 collected with the ALEPH detector in 1997 at a centre-of-mass energy of 183 GeV. The invariant mass distributions of reweighted Monte Carlo events are fitted separately to the experimental distributions in the qq\uafqq\uaf and all l\u3bdqq\uaf channels to give the following W masses:where the theory error represents the possible effects of final state interactions. The combination of these two measurements, including the LEP energy calibration uncertainty, give

Study of Fermion Pair Production in e+e−e^{+}e^{-} Collisions at 130-183 GeV

The cross sections and forward-backward asymmetries of hadronic and leptonic events produced in e+e- collisions at centre-of-mass energies of 130-183 GeV are presented. Results for ee, mumu, tautau, qq, bb and cc production show no significant deviation from the Standard Model predictions. This enable constraints to be set upon physics beyond the Standard Model such as four-fermion contact interactions, leptoquarks, Z' bosons and R-parity violating squarks and sneutrinos. Limits on the energy scale Lambda of eeff contact interactions are typically in the range from 2-10 TeV. Limits on R-parity violating sneutrinos reach masses of a few hundred GeV for large values of their Yukawa couplings

Measurement of the Hadronic Photon-Structure Function at LEP 1 for ll-Angle-Q2Q^{2} rr-Angle Values between 9.9 and 284 GeV2GeV^{2}

Inclusive gamma^*gamma interactions to hadronic final states where one scattered electron or positron is detected in the electromagnetic calorimeters have been studied in the LEP 1 data taken by ALEPH from 1991 to 1995. The event sample has been used to measure the hadronic structure function of the photon F_2^gamma in three bins with of 9.9, 20.7 and 284 GeV^2

One-prong τ\tau decays with kaons

One-prong $\tau$ decays into final states involving kaons are studied with about 161k $\tau^+\tau^-$ events collected by the ALEPH detector from 1991 to 1995. Charged kaons are identified by dE/dx measurement, while $K^0_L$'s are detected through their interaction in calorimeters. Branching ratios are measured for the inclusive mode, $B(\tau^-\rightarrow K^-X\nu_\tau)=(1.52 \pm 0.04\pm0.04)\%$, where $X$ can be any system of neutral particles, and for the exclusive modes \begin{center} \begin{tabular}{rcl} $B(\tau^-\to K^-\nu_\tau)$ &=& $(6.96\pm0.25\pm0.14)\times 10^{-3}$,\\ $B(\tau^-\to K^-\pi^0\nu_\tau)$ &=& $(4.44\pm0.26\pm0.24)\times 10^{-3}$,\\ $B(\tau^-\to K^-\pi^0\pi^0\nu_\tau)$ &=& $(0.56\pm0.20\pm0.15)\times 10^{-3}$,\\ $B(\tau^-\to K^-\pi^0\pi^0\pi^0\nu_\tau)$ &=& $(0.37\pm0.21\pm0.11)\times 10^{-3}$,\\ $B(\tau^-\to K^-K^{0}\nu_\tau)$ &=& $(1.62\pm0.21\pm0.11)\ times 10^{-3}$,\\ $B(\tau^-\to K^{-}K^{0}\pi^0\nu_\tau)$

Search for charginos and neutralinos in e+e−e^+ e^- collisions at center-of-mass energies near 183-GeV and constraints on the MSSM parameter space

Searches for charginos and neutralinos are performed with the data collected by the ALEPH detector at LEP at centre-of-mass energies near 183 GeV. In these searches, it is assumed that R-parity is conserved and that the lightest neutralino is the LSP. No evidence of a signal is observed in the 57 pb −1 accumulated, which excludes chargino and associated neutralino production up to the kinematic limit over large regions of the MSSM parameter space. Under the assumptions of common gaugino and common sfermion masses at the unification scale, the interplay between the chargino, neutralino and slepton exclusion limits allows a lower bound of 27 GeV/ c2 to be set on the mass of the lightest neutralino. Tighter constraints on the MSSM parameter space are obtained using in addition exclusions in the Higgs sector. Finally, the results are interpreted within the framework of minimal supergravity

Study of τ\tau decays involving kaons, spectral functions and determination of the strange quark mass

All ALEPH measurements of branching ratios of tau decays involving kaons are summarized including a combination of results obtained with K^0_S and K^0_L detection. The decay dynamics are studied, leading to the determination of contributions from vector K^*(892) and K^{*}(1410), and axial-vector K_1(1270) and K_1(1400) resonances. Agreement with isospin symmetry is observed among the different final states. Under the hypothesis of the conserved vector current, the spectral function for the K\bar{K}\pi mode is compared with the corresponding cross section for low energy e^+e^- annihilation, yielding an axial-vector fraction of (94^{+6}_{-8})% for this mode. The branching ratio for tau decay into all strange final states is determined to be B(\tau^-\to X^-(S=-1)\nu_\tau)=(28.7\pm1.2)\times 10^{-3}. The measured mass spectra of the strange tau decay modes are exploited to derive the S=-1 spectral function. A combination of strange and nonstrange spectral functions is used to determine the strange quark mass and nonperturbative contributions to the strange hadronic width. A method is developed to avoid the bad convergence of the spin zero hadronic component, with the result m_s(M_\tau^2)=(176^{\,+46}_{\, -57}) MeV/c^2. The evolution down to 1~GeV gives m_s(1~{\rm GeV}^2) = (234^{\,+61}_{\,-76})~{\rm MeV}/c^2