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Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment | 1989

Argus: A universal detector at DORIS II

H. Albrecht; U. Binder; P. Böckmann; G. Drews; R. Gläser; G. Harder; H. Hasemann; A. Krolzig; E. Michel; W. Reinsch; W. Schmidt-Parzefall; H. Schröder; H. Schulz; F. Selonke; E. Steinmann; R. Wurth; A. Drescher; B. Gräwe; W. Hofmann; D. Kamp; A. Markees; U. Matthiesen; H. Scheck; B. Spaan; J. Spengler; D. Wegener; R. Heller; K.R. Schubert; J. Stiewe; K. Strahl

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.


Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment | 1997

The H1 lead/scintillating-fibre calorimeter

R.D. Appuhn; C. Arndt; E. Barrelet; R. Barschke; U. Bassler; V. Boudry; R. Buchholz; F. Brasse; D. Bruncko; S. Chechelnitski; B. Claxton; G. Cozzika; J. Cvach; S. Dagoret-Campagne; W.D. Dau; H. Deckers; T. Deckers; F. Descamps; M. Dirkmann; J. Dowdell; V. Efremenko; E. Eisenhandler; A. Eliseev; G. Falley; J. Ferencei; B. Fominykh; K. Gadow; U. Goerlach; L.A. Gorbov; I. Gorelov

Abstract The backward region of the H1 detector has been upgraded in order to provide improved measurement of the scattered electron in deep inelastic scattering events. The centerpiece of the upgrade is a high-resolution lead/scintillating-fibre calorimeter. The main design goals of the calorimeter are: good coverage of the region close to the beam pipe, high angular resolution and energy resolution of better than 2% for 30 GeV electrons. The calorimeter should be capable of providing coarse hadronic energy measurement and precise time information to suppress out-of-time background events at the first trigger level. It must be compact due to space restrictions. These requirements were fulfilled by constructing two separate calorimeter sections. The inner electromagnetic section is made of 0.5 mm scintillating plastic fibres embedded in a lead matrix. Its lead-to-fibre ratio is 2.3:1 by volume. The outer hadronic section consists of 1.0 mm diameter fibres with a lead-to-fibre ratio of 3.4:1. The mechanical construction of the new calorimeter and its assembly in the H1 detector are described.


Physics Letters B | 1990

Search for hadronic b→u decays

H. Albrecht; W. Funk; G. Harder; A. Babaev; K. Reim; L. Jönsson; C. Geyer; Sally Seidel; B. Spaan; R.D. Appuhn; C. E. K. Charlesworth; S. Werner; A. Nippe; S. Khan; V. Shevchenko; K.W. Edwards; M. Paulini; Yu. Zaitsev; B. Fominykh; V. Chistilin; R. Waldi; T. Ruf; G. Herrera; R. Childers; G. Schweda; W. Hofmann; J. Stiewe; V. Lyubimov; A. Drescher; M. Schäfer

Using the ARGUS detector at the e+e− storage ring DORIS II at DESY, we searched for b→u transitions in exclusive hadronic B meson decays. A systematic analysis of B decays into pions has been performed for decay modes with 2–7 pions in the final state. In none of the decays a positive signal was observed. The upper limits obtained on various branching ratios are consistent with the current model predictions.


Physics Letters B | 1990

Observation of Semileptonic Charmless B Meson Decays

H. Albrecht; W. Funk; G. Harder; A. Babaev; K. Reim; L. Jönsson; C. Geyer; Sally Seidel; B. Spaan; R.D. Appuhn; C. E. K. Charlesworth; S. Werner; A. Nippe; S. Khan; V. Shevchenko; K.W. Edwards; M. Paulini; Yu. Zaitsev; B. Fominykh; V. Chistilin; R. Waldi; T. Ruf; G. Herrera; R. Childers; G. Schweda; W. Hofmann; J. Stiewe; V. Lyubimov; A. Drescher; M. Schäfer

Abstract A detailed study of the lepton momentum spectrum in υ (4 S ) decays has been made using the ARGUS detector at the DORIS II e + e − storage ring at DESY. In the region from 2.3 to 2.6 GeV/ c , which is above the endpoint for contributions from B decays via b → c transitions, we observe 41±10 events in excess of known backgrounds. These events are interpreted as a signal for b → u transitions. A model dependent value of 0.10±0.01 is obtained for the ratio of Cabibbo-Kobayashi-Maskawa matrix elements | V ub |/| V cv| , using the Altarelli et al. model.


Physics Letters B | 1988

Observation of charmless B meson decays

H. Albrecht; P. Böckmann; R. Gläser; G. Harder; A. Krüger; A. Nippe; M. Schäfer; W. Schmidt-Parzefall; H. Schröder; H. Schulz; F. Sefkow; J. Spengler; R. Wurth; A. Yagil; R.D. Appuhn; A. Drescher; D. Kamp; H. Kolanoski; R. Mankel; U. Matthiesen; H. Scheck; G. Schweda; B. Spaan; A. Walther; D. Wegener; J. C. Gabriel; T. Ruf; S. Schael; K.R. Schubert; J. Stiewe

Abstract Using the ARGUS detector at the e + e − storage ring DORIS II, we have observed charmless decays of B mesons into the final states ppπ ± and ppπ + π − . The significance of the signal corresponds to more than five standard deviations. The branching ratios are (5.2±1.4±1.9)×10 −4 for the three-body and (6.0±2.0±2.2)×10 −4 for the four-body final state. These decays cannot proceed via the dominant b→c transitions, and we show that they are not the result of penguin-type processes. Thus, the observed decays must represent b→u quark transitions. Consequently, the Kobayashi-Maskawa matrix element V ub is non-zero.


Physics Letters B | 1987

B meson decays into charmonium states

H. Albrecht; A.A. Andam; U. Binder; P. Böckmann; R. Gläser; G. Harder; A. Krüger; A. Nippe; M. Schäfer; W. Schmidt-Parzefall; H. Schröder; H. Schulz; R. Wurth; A. Yagil; J.P. Donker; A. Drescher; D. Kamp; H. Kolanoski; U. Matthiesen; H. Scheck; B. Spaan; J. Spengler; D. Wegener; J. C. Gabriel; T. Ruf; K.R. Schubert; J. Stiewe; K. Strahl; R. Waldi; K.W. Edwards

Abstract Using the ARGUS detector at the e +e− storage ring DORIS II, we have studied the colour-suppressed decays B → J ψ X and B→ψ′ X. We find the inclusive branching ratios for these two channels to be (1.07±0.16±0.19) % and (0.46±0.17±0.11) %, respectively. From a sample of reconstructed exclusive events the masses of the B0 and B+ mesons are determined to be (5279.5±1.6±3.0) MeV c 2 and (5278.5±1.8±3.0) MeV c 2 , respectively. Branching ratios are determined from five events of the type B 0 → J ψ K ∗0 and three of B+→J/ψ K+. In the same data sample a search for B0→e+e−, μ+μ− and μ±e∓ leads to upper limits for such decays.


Physics Letters B | 1990

Study of inclusive semileptonic B meson decays

H. Albrecht; H. Ehrlichmann; R. Gläser; G. Harder; A. Krüger; A. Nau; A. W. Nilsson; A. Nippe; T. Oest; M. Reidenbach; M. Schäfer; W. Schmidt-Parzefall; H. Schröder; H. Schulz; F. Sefkow; R. Wurth; R.D. Appuhn; A. Drescher; C. Hast; G. Herrera; H. Kolanoski; A. Lange; A. Lindner; R. Mankel; H. Scheck; M. Schieber; G. Schweda; B. Spaan; A. Walther; D. Wegener

Abstract Using the ARGUS detector at the e + e − storage ring DORIS-II, we have measured the inclusive semileptonic decays of B-mesons into electrons and muons. The data originate from 220.5 events/pb on the ϒ(4S) resonance. We find BR (B→e + v e X = (10.3 ± 0.6 ± 0.2)% and BR (B→ μ + v μ X) = (10.0 ± 0.6 ± 0.2)% using the model of Altarelli et al. for extrapolating over all lepton momenta, and BR (B→e + v e X) = (9.9±0.6)%, BR(B→ μ + v μ X) = (9.7±0.6)% using the model of Grinstein et al. For semileptonic decays into baryons, we obtain an upper limit of BR ( B → p e + v X ) CL ) .


Physics Letters B | 1991

Reconstruction of semileptonic b ---> u decays

H. Albrecht; W. Funk; G. Harder; A. Babaev; K. Reim; L. Jönsson; C. Geyer; Sally Seidel; B. Spaan; R.D. Appuhn; A. Nau; C. E. K. Charlesworth; S. Werner; A. Nippe; S. Khan; V. Shevchenko; K.W. Edwards; M. Paulini; Yu. Zaitsev; B. Fominykh; V. Chistilin; R. Waldi; T. Ruf; G. Herrera; R. Childers; G. Schweda; W. Hofmann; J. Stiewe; V. Lyubimov; A. Drescher

Abstract Using the ARGUS detector at the e+ e− storage ring DORIS II at DESY we have updated our result on charmless semileptonic B decays and searched for direct evidence for b→u transitions through reconstruction of complete events. This approach has successfully identified two ϒ (4S) events which contain B meson decays to a non-charm final state. In one case, a B0 meson is found in the channel π + μ − ν , while in the other a decay B+→ωμ+ν is seen. These events show that the previously observed signal of charmless semileptonic B decays is due to b→u transitions from which we obtain | V ub V cb | = 0.11±0.012 using the model of Altarelli et al.


Physics Letters B | 1990

Determination of the Michel parameter in tau decay

H. Albrecht; H. Ehrlichmann; G. Harder; A. Krüger; A. Nau; A. W. Nilsson; A. Nippe; T. Oest; M. Reidenbach; M. Schäfer; W. Schmidt-Parzefall; H. Schröder; H. Schulz; F. Sefkow; R. Wurth; R.D. Appuhn; A. Drescher; C. Hast; G. Herrera; H. Kolanoski; A. Lange; A. Lindner; R. Mankel; H. Scheck; M. Schieber; G. Schweda; B. Spaan; A. Walther; D. Wegener; M. Paulini

Abstract Using the ARGUS detector at the DORIS II e+e− storage ring we have studied the electron and muon energy spectra in τ − → e − ν ν and τ − →μ − ν ν decays. The measured value of the Michel parameter, ρ=0.742±0.035±0.020, is in good agreement with a standard V-A coupling at the τ-ντ-W vertex. Pure V, A and V + A couplings are completely excluded by this measurement. Upper limits have been obtained for two-body tau decays, including final states with a Goldstone boson.


Physics Letters B | 1991

Search for b→s.gluon in B meson decays

H. Albrecht; R. Gläser; G. Harder; A. Krüger; A. Nippe; T. Oest; M. Reidenbach; M. Schäfer; W. Schmidt-Parzefall; H. Schröder; H. Schulz; F. Sefkow; R. Wurth; R.D. Appuhn; A. Drescher; C. Hast; G. Herrera; H. Kolanoski; A. Lange; A. Lindner; R. Mankel; H. Scheck; G. Schweda; B. Spaan; A. Walther; D. Wegener; M. Paulini; K. Reim; U. Volland; H. Wegener

Abstract Using the ARGUS detector at the e + e − storage ring DORIS II at DESY, a search for penguin decays of B mesons involving b→s gluon has been performed. No evidence for the penguin mechanism was found and a number of upper limits are quoted.

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A. Drescher

Technical University of Dortmund

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B. Spaan

Technical University of Dortmund

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R.D. Appuhn

Technical University of Dortmund

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G. Schweda

Technical University of Dortmund

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G. Herrera

Technical University of Dortmund

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H. Scheck

Technical University of Dortmund

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R. Mankel

Technical University of Dortmund

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H. Kolanoski

Humboldt University of Berlin

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