Showing papers by "Werner Hofmann published in 1989"
01 Feb 1989-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: The ARGUS detector as mentioned in this paper was designed as a universal tool to investigate final states from e + e − annihilation processes in the energy range of the ϒ resonances, and has since successfully taken data at the 2S, 3S, and 4S energies, and in the nearby continuum.
Abstract: The detector ARGUS has been designed as a universal tool to investigate final states from e + e − annihilation processes in the energy range of the ϒ resonances. ARGUS started operation in October 1982 and has since successfully taken data at the ϒ(1S), ϒ(2S) and ϒ(4S) energies, and in the nearby continuum. The detector combines excellent charged particle identification and good photon energy resolution over more than 90% of the full solid angle. A particle originating from the interaction vertex and leaving the beam tube traverses the following components: the vertex drift chamber, the main drift chamber which determines its momentum and specific ionization, the time-of-flight system through which its velocity is determined, and the electromagnetic calorimeter. Muons pass through the magnet coils and the flux return yoke and finally hit the muon chamber system which surrounds the detector. The momentum resolution of ARGUS is σ (p T ) P T = (0.01 2 + (0.009p T [ GeV /c]) 2 ) 1 2 , the photon energy resolution in the barrel shower counters is σ (E) E = ( 0.072 2 +0.065 2 E[ GeV ] ) 1 2 . Combining the information from all p devices, more than 80% of all charged hadrons can be recognized unambiguously. The electron-hadron and muon-hadron rejection rates are 1:200 and 1:50 respectively.
138 citations
Technical University of Dortmund1, University of Erlangen-Nuremberg2, Heidelberg University3, Max Planck Society4, Natural Sciences and Engineering Research Council5, National Science Foundation6, Karlsruhe Institute of Technology7, University of Ljubljana8, Swedish Research Council9, United States Department of Energy10
TL;DR: In this paper, a decay angular analysis of the D∗ (2420), seen in the final state D ∗(2010)+π−, was performed using data collected with the ARGUS detector.
34 citations
TL;DR: Using the ARGUS detector at the DORIS II e + e − storage ring at DESY, the authors obtained evidence for a new charmed-strange meson which decays into D *+ K 0.
22 citations
Technical University of Dortmund1, University of Erlangen-Nuremberg2, Heidelberg University3, Max Planck Society4, Natural Sciences and Engineering Research Council5, National Science Foundation6, Karlsruhe Institute of Technology7, University of Ljubljana8, Swedish Research Council9, United States Department of Energy10
TL;DR: Using the ARGUS detector at the DORIS II e+e- storage ring at DESY, this article observed a new charmed meson of mass (2469±4±6) MeV/c2, decaying to D0π+.
17 citations
Technical University of Dortmund1, University of Erlangen-Nuremberg2, Heidelberg University3, Max Planck Society4, Natural Sciences and Engineering Research Council5, National Science Foundation6, Karlsruhe Institute of Technology7, University of Ljubljana8, Swedish Research Council9, United States Department of Energy10
TL;DR: In this paper, the ARGUS detector at the e+e- storage ring DORIS II was used to determine the ratio of semileptonic branching ratios of B+ and B0 mesons.
16 citations
University of Tokyo1, University of California, Berkeley2, University of California, Santa Barbara3, Johns Hopkins University4, University of California, Los Angeles5, Ames Laboratory6, University of California, Riverside7, University of California, San Diego8, University of Massachusetts Amherst9, University of California, Davis10
TL;DR: In this article, the authors report a measurement of the luminosity of the TPC/Two-Gamma storage ring at SLAC, where they identify approximately 45 events that are consistent with the center-of-mass energy of one of the photons.
Abstract: We report a measurement of the ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{e}^{+}{e}^{\ensuremath{-}}p\overline{p}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ process with the TPC/Two-Gamma facility at the PEP ${e}^{+}{e}^{\ensuremath{-}}$ storage ring at SLAC. Forty-five $p\overline{p}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ events were identified in data corresponding to an integrated ${e}^{+}{e}^{\ensuremath{-}}$ luminosity of 142 ${\mathrm{pb}}^{\ensuremath{-}1}$. The cross section for $\ensuremath{\gamma}\ensuremath{\gamma}\ensuremath{\rightarrow}p\overline{p}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ is given both as a function of the $\ensuremath{\gamma}\ensuremath{\gamma}$ center-of-mass energy ${W}_{\ensuremath{\gamma}\ensuremath{\gamma}}$, with ${W}_{\ensuremath{\gamma}\ensuremath{\gamma}}$ between 2.5 and 5.5 GeV, and as a function of the in variant mass squared ${q}^{2}$ of one of the photons, with $\ensuremath{-}{q}^{2}l7$ Ge${\mathrm{V}}^{2}$. This cross section falls much less rapidly with ${W}_{\ensuremath{\gamma}\ensuremath{\gamma}}$ than does the cross section for a similar process, $\ensuremath{\gamma}\ensuremath{\gamma}\ensuremath{\rightarrow}p\overline{p}$. No ${\ensuremath{\Delta}}^{0}{\overline{\ensuremath{\Delta}}}^{0}$ production is observed, and only a small fraction of the events at low ${W}_{\ensuremath{\gamma}\ensuremath{\gamma}}$ is consistent with $\ensuremath{\gamma}\ensuremath{\gamma}\ensuremath{\rightarrow}{\ensuremath{\Delta}}^{++}{\overline{\ensuremath{\Delta}}}^{\ensuremath{-}\ensuremath{-}}$, ${\ensuremath{\Delta}}^{++}\overline{p}{\ensuremath{\pi}}^{\ensuremath{-}}$, or ${\overline{\ensuremath{\Delta}}}^{\ensuremath{-}\ensuremath{-}}p{\ensuremath{\pi}}^{+}$. In an expanded search through the same data, four events compatible with either $\ensuremath{\Lambda}\overline{\ensuremath{\Lambda}}(\ensuremath{\Lambda}\ensuremath{\rightarrow}p{\ensuremath{\pi}}^{\ensuremath{-}})$ or ${\ensuremath{\Sigma}}^{0}\overline{\ensuremath{\Lambda}}({\ensuremath{\Sigma}}^{0}\ensuremath{\rightarrow}\ensuremath{\Lambda}\ensuremath{\gamma})$ production were found.
7 citations
TL;DR: In this paper, the ARGUS detector at DORIS II was used to detect Δ(1232) ++ and Δ ( 1232 ) + + ¯ baryons in e + e − annihilation at energies around 10 GeV.
7 citations
University of Tokyo1, University of California, Berkeley2, University of California, Santa Barbara3, Johns Hopkins University4, University of California, Los Angeles5, Ames Laboratory6, University of California, Riverside7, Stanford University8, University of California, San Diego9, University of Massachusetts Amherst10, Iowa State University11, University of California, Davis12
TL;DR: In this paper, the authors studied the rapidity distributions of charged particles produced by collinear gluons at 29 GeV and found that there is a significant dip in rapidity distribution aty≈0 for events with low sphericity.
Abstract: In the study of rapidity distributions of charged pions produced ine
+
e
− annihilation at 29 GeV, we observe a significant dip in the rapidity distributions aty≈0 for events with low sphericity. A comparison of data with several QCD-based phenomenological models strongly suggests that this structure is related to the emission of multiple soft and/or collinear gluons.
3 citations
TL;DR: In this paper, the average charge of particles in the cosmic radiation near 1014eV can be determined by observing the effect of the solar magnetic field on the Sun's shadow in the angular distribution of energetic primary cosmic ray particles.
Abstract: According to a proposal of Lloyd-Evans (1985), the average charge of particles in the cosmic radiation near 1014eV can be determined by observing the effect of the solar magnetic field on the Sun's shadow in the angular distribution of energetic primary cosmic ray particles. This suggestion is shown to be realizable with a new type of EAS-array proposed for the purpose of high energy γ-ray astronomy. The same measurement provides information on the integrated strength of the solar magnetic field. As the array will be sensitive and provide good angular resolution down to a few times 1012eV, more detailed results on the primary composition near 1013eV can be obtained by investigating the shape of the shadow of the Moon as affected by the geomagnetic field.
2 citations