1,721,111 research outputs found
The AMS-02 Detector Operation in Space
No full textThe Alpha Magnetic Spectrometer is a large acceptance instrument conceived for the search of primordial anti-matter and dark matter on board the International Space Station (ISS) orbiting at 400 km from the earth surface. Nine layers of double sided silicon microstrip detectors track with a single point resolution of 10 μm the charged particle trajectories bent in the magnetic field of a permanent magnet. Redundant measurements of the charge magnitude, velocity, momentum and energy of the cosmic rays are performed by the different detectors integrated in AMS-02.
The large acceptance and a long exposure time, matching the ISS operational lifetime, will allow
AMS-02 to collect a wealth of data to study with unprecedented accuracy the composition and the energy spectrum of charged CRs and gammas up to the TeV energy scale. Launched with the STS-134 mission of the Shuttle Endeavour on May 16th 2011, AMS-02 has been installed on May 19th on the ISS and it is continuously taking data since then. In this contribution we will revue the characteristics of the instrument and report on the AMS-02 status in orbit
Search for charged Higgs bosons in e+e− collisions at s√ = 189-GeV.
No full textAbstract: A search for pair-produced charged Higgs bosons is performed with the L3 detector at LEP using data collected at a centre-of-mass energy of 188.6 GeV, corresponding to an integrated luminosity of 176.4 pb^-1. Higgs decays into a charm and a strange quark or into a tau lepton and its associated neutrino are considered. The observed events are consistent with the expectations from Standard Model background processes. A lower limit of 65.5 GeV on the charged Higgs mass is derived at 95 % confidence level, independent of the decay branching ratio Br(H^{+/-} -> tau nu)
Ultra-thin, High-precision Flex Cable For the L3 Silicon Microvertex Detector
No full textWe describe an ultra-thin, high-precision Kapton flex cable for use as a signal router in the L3 Silicon Microvertex Detector. The excellent mechanical and electrical properties of this cable make it dimensionally stable against temperature and humidity changes, as well as maintaining cross talk below 3% between adjacent lines. Electron beam photolithography and chemical etching technology have produced a cable with typically 11 mu m wide lines spanning continuous lengths up to 14 cm, with sufficient alignment accuracy to match both input and output pads over the entire length of the detector. Electroplated input and output pads allow automated wire bonding with excellent pull strength and high efficiency
Measurement of the Inclusive B-]tau-nu-x Branching Ratio
No full textUsing the L3 detector, the branching ratio BR(b --> taunuX) has been measured using a sample of Z --> bbBAR events tagged by high momentum and high transverse momentum leptons in one hemisphere and with missing energy in the opposite hemisphere. From a sample of 948000 hadronic events we find BR(b --> taunuX) = (2.4 +/- 0.7 (stat.) +/- 0.8 (syst.))%
An S-matrix Analysis of the Z-resonance
No full textThe S matrix ansatz is a rigorously model independent approach to describe the cross-sections and asymmetries in e+ e- annihilation. Using the cross-sections and asymmetries measured with the L3 detector during the 1990 and 1991 running period, we determine the mass and the width of the Z boson, the contributions of the Z exchange and of the gammaZ interference. Including the polarization of the tau lepton in the analysis, the leptonic helicity amplitudes of the scattering process are determined assuming lepton universality. The results are compared with other model independent ansatzes as realized in ZFITTER. A systematic bias of the Z mass due to the gammaZ interference term is detected, which leads to an underestimation of the error on m(Z) for model independent determinations
Search For the Neutral Higgs Boson At Lep
No full textA search for the standard model neutral Higgs boson is described. Data collected during 1990 and 1991, corresponding to 408 000 hadronic decays of the Z0, were used. At the 95% confidence level we exclude the existence of the minimal standard model Higgs boson in the mass range 0 less-than-or-equal-to M(H0) < 52 GeV
An Improved Measurement of B(0)-(b)bar(0) Mixing In Z(0) Decays
No full textA more precise determination of the B0-B0BAR mixing parameter in Z0 decays based on a fourfold increase in statistics has been made using the 1990 and 1991 L3 data. The analysis of the dilepton events, muons and electrons, gives: chi(B) = 0. 121 +/- 0.017 (stat) +/- 0.006 (sys). Using the value of chi(d) measured at the UPSILON(4S) we derive the following limit for chi(s): chi(S) > 0.16 (90% CL)
Test Beam Results From the Prototype L3 Silicon Microvertex Detector
No full textWe report test beam results on the overall system performance of two modules of the L3 Silicon Microvertex Detector exposed to a 50 GeV pion beam. Each module consists of two AC coupled double-sided silicon strip detectors equipped with VLSI readout electronics. The associated data acquisition system comprises an 8 bit FADC, an optical data transmission circuit, a specialized data reduction processor and a synchronization module. A spatial resolution of 7.5 mum and 14 mum for the two coordinates and a detection efficiency in excess of 99% are measured
- …
