Test beam results of a stereo preshower integrated in the liquid argon accordion calorimeter

This paper describes the construction of an integrated preshower within the RD3 liquid argon accordion calorimeter. It has a stereo view which enables the measurement of two transverse coordinates. The prototype was tested at CERN with electrons, photons and muons to validate its capability to work at LHC (Energy resolution, impact point resolution, angular resolution, π o γ rejection). (Elsevier

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

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})%

KS0K^{0}_{S} production in τ\tau decays

From a sample of about 160k \mbox{Z}\!\!\to\!\!\tau^+\tau^- candidates collected with the ALEPH detector at LEP between 1991 and 1995, $\tau$ lepton decays involving $K^0_S\!\to\!\pi^+\pi^-$ are studied. The $K^0_SK^0_L$ associated production in $\tau$ decays is also investigated. The branching ratios are measured for the inclusive decay $B(\tau^-\!\!\to\!\!K^0_SX^-\nu_\tau)=(9.70\!\pm\!0.58\!\pm\!0.62)\ times10^{-3}$ , where $X^-$ can be anything, and for the exclusive decays \begin{center} \begin{tabular}{rcl} $B(\tau^-\!\!\to\!\!\overline{K}^0\pi^-\nu_\tau)$&=&$(8.55\!\pm\!1. 17\! \pm\!0.66)\times10^{-3}$,\\ $B(\tau^-\!\!\to\!\!\overline{K}^0\pi ^-\pi^0\nu_\tau)$&=&$(2.94\!\pm\! 0.73\!\pm\!0.37)\times10^{-3}$, \\ $B(\tau^-\!\!\to\!\!\overline{K} ^0K^-\nu_\tau)$&=&$(1.58\!\pm\!0.42\!\pm\! 0.17)\times10^{-3}$, \\ $B(\tau^-\!\!\to\!\!\overline{K}^0K^-\pi^0\nu_\tau)$&=&$(1.52\!\pm\ !0.76\! \pm\!0.21)\times10^{-3}$. \\ \end{tabular} \end{center} The decays $\tau^-\!\!\to\!\!K^0_SK^0_L\pi^-\nu_\tau$ is studied for the first time, giving a branching ratio \begin{center} \begin{tabular}{rcl} $B(\tau^-\!\!\to\!\!K^0_SK^0_L\pi^-\nu_\tau)$&=&$(1.01\!\pm\!0.23\!\pm\!0.13)\times10^{-3}.$ \end{tabular} \end{center} The channels $\tau^-~\!\!\!\to\!\!\!~K^0_SK^0_S\pi^-\nu_\tau~$, $\tau^-~\!\!\!\to\!\!\!~K^0_SK^0_S\pi^-\pi^0\nu_\tau~$, $\tau^-~\!\!\!\to\!\!\!~K^0_SK^0_L\pi^-\pi^0\nu_\tau~$, $\tau^-~\!\!\!\to\!\!\!~\overline{K}^0\pi^-\pi^0\pi^0\nu_\tau$, $\tau^-~\!\!\!\to\!\!\!~K^0K^-\pi^0\pi^0\nu_\tau$ and $\tau^-~\!\!\!\to\!\!\!~K^0h^+h^-h^-\nu_\tau$ are also investigated. In addition, mass spectra in the $K^0_Sh^-$ and $K^0_Sh^-\pi^0$ final states are analysed to provide information on the intermediate states produced in the decays