The EUDET-project was launched to create an infrastructure for developing and testing new and advanced detector technologies to be used at a future linear collider. The aim was to make possible experimentation and analysis of data for institutes, which otherwise could not be realized due to lack of resources. The infrastructure comprised an analysis and software network, and instrumentation infrastructures for tracking detectors as well as for calorimetry.
A data acquisition (DAQ) system has been developed which will read out and control calorimeters serving as prototype systems for a future detector at an electron-positron linear collider. This is a modular, flexible and scalable DAQ system in which the hardware and signals are standards-based, using FPGAs and serial links. The idea of a backplaneless system was also pursued with a commercial development board housed in a PC and a chain of concentrator cards between it and the detector forming the basis of the system. As well as describing the concept and performance of the system, its merits and disadvantages are discussed.
A prototype silicon-tungsten electromagnetic calorimet er for an ILC detector was tested in 2007 at the CERN SPS test beam. Data were collected w ith electron and hadron beams in the energy range 8 to 80 GeV. The analysis described here fo cuses on the interactions of pions in the calorimeter. One of the main objectives of the CALICE p rogram is to validate the Monte Carlo tools available for the design of a full-sized detecto r. The interactions of pions in the Si-W calorimeter are therefore confronted with the predictions f various physical models implemented in theGEANT4 simulation framework.
A search for the production and non-standard decay of a Higgs boson, h, into four taus through intermediate pseudoscalars, a, is conducted on 683 pb−1 of data collected by the ALEPH experiment at centre-of-mass energies from 183 to 209 GeV. No excess of events above background is observed, and exclusion limits are placed on the combined production cross section times branching ratio, \( {\xi^2} = \frac{{\sigma \left( {{\text{e}^{+} }{\text{e}^{-} } \to {\text{Zh}}} \right)}}{{{\sigma_{\text{SM}}}\left( {{\text{e}^{+} }{\text{e}^{-} } \to {\text{Zh}}} \right)}} \times B\left( {h \to {\text{aa}}} \right) \times B{\left( {{\text{a}} \to {\tau^{+} }{\tau^{-} }} \right)^2} \). For m h < 107 GeV/c 2 and 4 < m a < 10 GeV/c 2, ξ 2 > 1 is excluded at the 95% confidence level.
A prototype silicon-tungsten electromagnetic calorimeter for an ILC detector was tested in 2007 at the CERN SPS test beam. Data were collected with electron and hadron beams in the energy range 8 to 80 GeV. The analysis described here focuses on the interactions of pions in the calorimeter. One of the main objectives of the CALICE program is to validate the Monte Carlo tools available for the design of a full-sized detector. The interactions of pions in the Si-W calorimeter are therefore confronted with the predictions of various physical models implemented in the GEANT4 simulation framework.
An analog hadron calorimeter (AHCAL) prototype of 5.3 nuclear interaction lengths thickness has been constructed by members of the CALICE Collaboration. The AHCAL prototype consists of a 38-layer sandwich structure of steel plates and highly-segmented scintillator tiles that are read out by wavelength-shifting fibers coupled to SiPMs. The signal is amplified and shaped with a custom-designed ASIC. A calibration/monitoring system based on LED light was developed to monitor the SiPM gain and to measure the full SiPM response curve in order to correct for non-linearity. Ultimately, the physics goals are the study of hadron shower shapes and testing the concept of particle flow. The technical goal consists of measuring the performance and reliability of 7608 SiPMs. The AHCAL was commissioned in test beams at DESY and CERN. The entire prototype was completed in 2007 and recorded hadron showers, electron showers and muons at different energies and incident angles in test beams at CERN and Fermilab.
The ZZ production cross section is measured from a data sample corresponding to a total integrated luminosity of 452 pb−1, collected by the ALEPH experiment at LEP at centre-of-mass energies from 192 to 209 GeV. Individual cross sections, extracted at six centre-of-mass energies, are found to be in agreement with Standard Model calculations. The results are used to set limits on anomalous neutral gauge couplings.
The CALICE collaboration is studying the design of high performance electromagnetic and hadronic calorimeters for future International Linear Collider detectors. For the electromagnetic calorimeter, the current baseline choice is a high granularity sampling calorimeter with tungsten as absorber and silicon detectors as sensitive material. A ``physics prototype'' has been constructed, consisting of thirty sensitive layers. Each layer has an active area of 18 × 18 cm2 and a pad size of 1 × 1 cm2. The absorber thickness totals 24 radiation lengths. It has been exposed in 2006 and 2007 to electron and hadron beams at the DESY and CERN beam test facilities, using a wide range of beam energies and incidence angles. In this paper, the prototype and the data acquisition chain are described and a summary of the data taken in the 2006 beam tests is presented. The methods used to subtract the pedestals and calibrate the detector are detailed. The signal-over-noise ratio has been measured at 7.63±0.01. Some electronics features have been observed; these lead to coherent noise and crosstalk between pads, and also crosstalk between sensitive and passive areas. The performance achieved in terms of uniformity and stability is presented.
Cross sections, angular distributions and forward-backward asymmetries are presented, of two-fermion events produced in e+e- collisions at centre-of-mass energies from 189 to 209 GeV at LEP, measured with the ALEPH detector. Results for e+e-, mu+mu-, tau+tau-, qq, bb and cc production are in agreement with the Standard Model predictions. Constraints are set on scenarios of new physics such as four-fermion contact interactions, leptoquarks, Z' bosons, TeV-scale quantum gravity and R-parity violating squarks and sneutrinos.
Inclusive beauty-quark production in two-photon collisions has been measured at LEP using an integrated luminosity of 698 pb-1 collected by the ALEPH detector with sqrt(s) between 130 and 209 GeV. The b quarks were identified using lifetime information. The cross section is found to be sigma(e+ e- --> e+ e- b \bar{b} X) = (5.4 +/- 0.8 (stat) +/- 0.8 (syst)) pb which is consistent with Next-to-Leading Order QCD.
A search for Higgs bosons produced in association with a fermion pair, and decaying to WW, is performed with the data collected by the ALEPH detector at centre-of-mass energies ranging from 191 to 209 GeV. The data correspond to an integrated luminosity of 453.2 pb-1. Thirteen exclusive selections are developed according to the different final state topologies. No statistically significant evidence for a Higgs boson decaying into a WW pair has been found. An upper limit is derived, as a function of the Higgs boson mass, on the product of the e+e-→Hff̄ cross section and the H→WW branching ratio. The data on the search for H→WW are combined with previously published ALEPH results on the search for H→γγ, to significantly extend the limits on the mass of a fermiophobic Higgs boson.
We present results of a search for the X(3872) in B0→X(3872)K0S,X(3872)→J/ψπ+π−, improved measurements of B−→X(3872)K−, and a study of the J/ψπ+π− mass region above the X(3872). We use 232×106 B¯¯¯B pairs collected at the Υ(4S) resonance with the BABAR detector at the PEP-II e+e− asymmetric-energy storage rings. The results include the 90% confidence interval 1.34×10−6
Deuteron and anti-deuteron production in Z decays has been observed in the ALEPH experiment at LER The production rate of anti-deuterons is measured to be (5.9 +/- 1.8 +/- 0.5) x 10(-6) per hadronic Z decay in the anti-deuteron momentum range from 0.62 to 1.03 GeV/c. The coalescence parameter B-2, which characterizes the likelihood of anti-deuteron production, is measured to be 0.0033 +/- 0.0013 GeV2 in Z decays. These measurements indicate that the production of anti-deuterons is suppressed in e(+)e(-) collisions compared to that in pp and photoproduction collisions. (c) 2006 Elsevier B.V. All rights reserved.
We measure the dependence of ${\overline{B}}^{0}\ensuremath{\rightarrow}{D}^{*+}{e}^{\ensuremath{-}}{\overline{\ensuremath{\nu}}}_{e}$ on the decay angles and momentum transfer. The data sample consists of $\ensuremath{\sim}86\ifmmode\times\else\texttimes\fi{}{10}^{6}$ $B\overline{B}$-pairs accumulated on the $\mathit{\ensuremath{\Upsilon}}(4\mathrm{S})$ resonance by the BABAR detector at the asymmetric ${e}^{+}{e}^{\ensuremath{-}}$ collider PEP-II. We specify the three form factors by two ratios ${R}_{1}$ and ${R}_{2}$, and by a single parameter ${\ensuremath{\rho}}^{2}$ characterizing the polynomial representing ${h}_{{A}_{1}}$, the function which describes the momentum-transfer dependence of the form factor ${A}_{1}$. We determine ${R}_{1}$, ${R}_{2}$, and ${\ensuremath{\rho}}^{2}$ using an unbinned maximum likelihood fit to the full decay distribution. The results are ${R}_{1}=1.396\ifmmode\pm\else\textpm\fi{}0.060\ifmmode\pm\else\textpm\fi{}0.035\ifmmode\pm\else\textpm\fi{}0.027$, ${R}_{2}=0.885\ifmmode\pm\else\textpm\fi{}0.040\ifmmode\pm\else\textpm\fi{}0.022\ifmmode\pm\else\textpm\fi{}0.013$, and ${\ensuremath{\rho}}^{2}=1.145\ifmmode\pm\else\textpm\fi{}0.059\ifmmode\pm\else\textpm\fi{}0.030\ifmmode\pm\else\textpm\fi{}0.035$. The stated uncertainties are the statistical from the data, statistical from the size of the Monte Carlo sample and the systematic uncertainty, respectively. In addition, based on this measurement, we give an updated value for the CKM matrix element $|{V}_{cb}|$.
We study the two-body decays of B+/- mesons to K+/- and a charmonium state X-c(c) over bar in a sample of 210.5 fb(-1) of data from the BABAR experiment. We perform measurements of absolute branching fractions B(B+/- -> K+/-Xc(c) over bar) using a missing mass technique, and report several new or improved results. In particular, the upper limit B(B+/- -> K+/-X(3872)) < 3.2 x 10(-4) at 90% C.L. and the inferred lower limit B(X(3872) -> J/psi pi(+)pi(-)) > 4.2% will help in understanding the nature of the recently discovered X(3872).
A review of the present status of the W boson mass and width measurements at LEP is presented. The analysis of the data collected in 1998 by the 4 LEP collaborations, corresponding to about 700 pb(-1), allows to reach an experimental uncertainty on the W boson mass measured at LEPII approaching the precision of the indirect results from the high precision electroweak measurements at LEPI.