Jürgen Ulbricht

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A precision measurement by the Alpha Magnetic Spectrometer on the International Space Station of the positron fraction in primary cosmic rays in the energy range from 0.5 to 350 GeV based on 6.8 × 10(6) positron and electron events is presented. The very accurate data show that the positron fraction is steadily increasing from 10 to ∼ 250  GeV, but, from 20(More)
We review the experimental limits on mass of excited fundamental particles and contact interaction energy scale parameters Λ for QCD, QED and electroweak reactions. In particular we have focused on the QED reaction measuring the differential cross-sections for the process e+e− → γγ(γ) at the energies from 91GeV to 202GeV using the data collected with the L3(More)
1 Department of Mathematics and Computer Science, University of Warmia and Mazury, Słoneczna 54, 10-710 Olsztyn, Poland 2 A.F. Ioffe Physico-Technical Institute, St. Petersburg 194021, Russia 3 TH Division, PH Department, CERN, 1211 Geneva 23, Switzerland 4 Laboratory of High Energy Physics, Department of Physics, Kyungpook National University, 1370 San(More)
The processes ee → nγ (n ≥ 2) are studied to estimate the total and differential cross sections of these reactions using the L3 data collected during 1991–1998 at energies ( √ s) in the range 91–183 GeV. The lower limits obtained at 95% CL are, on a contact interaction energy scale Λ > 1065 GeV, on the mass of an excited electron me∗ > 263 GeV. The upper(More)
We review the experimental limits on those hypothetical interactions where the fundamental particles could exhibit non point-like behavior. In particular we have focused on the QED reaction measuring the differential cross sections for the process ee → γγ(γ) at energies around 91 GeV and 209 GeV with data collected from the L3 detector from 1991 to 2001.(More)
The Alpha Magnetic Spectrometer (AMS-02) is a high energy particle physics experiment that will study cosmic rays in the ∼ 100MeV to 1TeV range and will be installed on the International Space Station (ISS) for at least 3 years. A first version of AMS-02, AMS-01, flew aboard the space shuttle Discovery from June 2 to June 12, 1998, and collected 10 cosmic(More)
The measurements of the QED reaction ee → γγ(γ) performed with the L3 detector are used to search for new physics phenomena beyond the Standard Model. No evidence for these phenomena is found and new limits on their parameters are set. First the reaction is used to constrain a model of an excited electron and second to study contact interactions. The total(More)
The process e+e− → γγ(γ) is well suited to test QED and to search for new physics phenomena, whose expected contribution with the increasing of energy. The measurements of this reaction with the L3 detector are used to constrain a model of an excited electron and to study contact interactions. No evidence for these phenomena is found and new limits on their(More)