Thermodynamic temperature assignment to the point of inflection of the melting curve of high-temperature fixed points

The thermodynamic temperature of the point of inflection of the melting transition of Re-C, Pt-C and Co-C eutectics has been determined to be 2747.84\u2009\ub1\u20090.35 K, 2011.43\u2009\ub1\u20090.18\u2009K and 1597.39\u2009\ub1\u20090.13\u2009K, respectively, and the thermodynamic temperature of the freezing transition of Cu has been determined to be 1357.80\u2009\ub1\u20090.08\u2009K, where the \ub1 symbol represents 95% coverage. These results are the best consensus estimates obtained from measurements made using various spectroradiometric primary thermometry techniques by nine different national metrology institutes. The good agreement between the institutes suggests that spectroradiometric thermometry techniques are sufficiently mature (at least in those institutes) to allow the direct realization of thermodynamic temperature above 1234\u2009K (rather than the use of a temperature scale) and that metal-carbon eutectics can be used as high-temperature fixed points for thermodynamic temperature dissemination. The results directly support the developing mise en pratique for the definition of the kelvin to include direct measurement of thermodynamic temperature.Peer reviewed: YesNRC publication: Ye

A study of the decay width difference in the Bs0−B‾s0B^{0}_{s}-\overline{B}^{ 0}_{s} system using ϕϕ\phi\phi correlations

In a data sample of about four million hadronic Z decays recorded with the ALEPH detector from 1991 to 1995, the $B^{0}_{s} \to D^{(*)+}_{s}D^{(*)-}_{s}$ decay is observed, based on tagging the nal state with two $\phi$ mesons in the same hemisphere. The $D^{(*)+}_{s}D^{(*)-} _{s}$ final state is mostly CP even and corresponds to the short-lived $B^0$ mass eigenstate. The branching ratio of this decay is measured to be BR$(B^{0}_{s}(short) \to D^{(*)+}_{s}D^{(*)-}_{s}) = (23\pm 10^{+19}_{-9})$. A measurement of the lifetime of the $B^0$(short) gives 1.27$\pm$ 0.33$\pm$ 0.07 ps. The lifetime and branching ratio measurements allow two essentially independent estimates to be made of the relative decay width difference $\Delta\Gamma/\Gamma$ in the $B^{0}_{s}-\overline{B}^{0}_{s}$ system, corresponding to an average value $\Delta\Gamma/\Gamma = (25^{+21}_{-14})%

Searches for Charginos and Neutralinos in e+e−e^+ e^- Collisions at s\sqrt{s} = 161 and 172 GeV

The data recorded by the ALEPH detector at centre-of-mass energies of 161, 170, and 172 GeV are analysed for signals of chargino and neutralino production. No evidence of a signal is found, although candidate events consistent with the expectations from Standard Model processes are observed. Limits at 95% C.L. on the production cross sections are derived and bounds on the parameters of the Minimal Supersymmetric Standard Model are set. The lower limit on the mass of the lightest chargino is 85.5 GeV/c^2 for gaugino-like charginos (mu = -500 GeV/c^2), and 85.0 GeV/c^2 for Higgsino-like charginos (M_2 = 500 GeV/c^2), for heavy sneutrinos (M(snu) 200 GeV/c^2) and tanb = sqrt(2). The effect of light sleptons on chargino and neutralino limits is investigated. The assumptions of a universal slepton mass and a universal gaugino mass are relaxed, allowing less model-dependent limits to be obtained

Searches for Charginos and Neutralinos in e+e−e^+ e^- Collisions at s\sqrt{s} = 161 and 172 GeV

The data recorded by the ALEPH detector at centre-of-mass energies of 161, 170, and 172 GeV are analysed for signals of chargino and neutralino production. No evidence of a signal is found, although candidate events consistent with the expectations from Standard Model processes are observed. Limits at 95% C.L. on the production cross sections are derived and bounds on the parameters of the Minimal Supersymmetric Standard Model are set. The lower limit on the mass of the lightest chargino is 85.5 GeV/c^2 for gaugino-like charginos (mu = -500 GeV/c^2), and 85.0 GeV/c^2 for Higgsino-like charginos (M_2 = 500 GeV/c^2), for heavy sneutrinos (M(snu) 200 GeV/c^2) and tanb = sqrt(2). The effect of light sleptons on chargino and neutralino limits is investigated. The assumptions of a universal slepton mass and a universal gaugino mass are relaxed, allowing less model-dependent limits to be obtained

Updated measurement of the τ\tau lepton lifetime

A new measurement of the mean lifetime of the tau lepton is presented. Three different analysis methods are applied to a sample of 90000 tau pairs, collected in 1993 and 1994 with the ALEPH detector at LEP. The average of this measurement and those previously published by ALEPH is tau_tau = 290.1 +- 1.5 +- 1.1 fs