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  • 1
    Electronic Resource
    Electronic Resource
    Bound states of the muon-antimuon system: Lifetimes and hyperfine splitting (1998)
    Springer
    Journal of experimental and theoretical physics 86 (1998), S. 226-236 
    Details
    ISSN: 1090-6509
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We examine the properties of an atomic system consisting of a muon and antimuon. Expressions are derived for the probability of decay and the hyperfine splitting of the lower levels with allowance for the leading radiative corrections, which are of relative order α. The results for the lifetimes and the ground-state energy are τ(13 S 1)=1.7907(8)×10−12 s, τ(11 S 0)=0.59547(33)×10−12 s, and E hfs (1s)=4.23284(35)×107 MHz. The relative probabilities for the various decay channels are calculated; in particular, for the 1 3 S 1 level it is found that Γ (μμ→eeγ)/Γ(μμ→ee)≈15%. Finally, possible applications are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.558448
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  • 2
    Electronic Resource
    Electronic Resource
    Rapidity dependence of thermal dileptons resulting from hadronizing quark-gluon matter with finite baryon charge (1995)
    Springer
    The European physical journal 353 (1995), S. 71-77 
    Details
    ISSN: 1434-601X
    Keywords: 25.75.+r ; 12.38.Mh ; 24.85.+p
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The influence of a non-vanishing baryon charge on the rapidity distribution of dileptons produced in ultrarelativistic heavy-ion collisions is studied. We employ a frozen motion model with scaling invariant expansion of the hadronizing quark-gluon plasma as well as a realistic rapidity distribution of secondary particles (i.e., pions and baryons) expected for RHIC energies. We demonstrate a sizeable suppression of the thermal dilepton yield at large rapidities due to the finite baryon density. This affects the most favorable rapidity window for using dileptons for the diagnostic of the quark-gluon plasma and the early temperature distribution of the hot reaction zone. To discriminate the thermal dileptons from Drell-Yan background we propose to utilize the dilepton yield scaled suitably by the pion multiplicity as function of rapidity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01297729
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  • 3
    Electronic Resource
    Electronic Resource
    Coulomb corrections to Delbrück scattering (1995)
    Springer
    The European physical journal 353 (1995), S. 273-277 
    Details
    ISSN: 1434-601X
    Keywords: 12.20.Ds ; 13.60.Fz
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We numerically evaluate an expression for the Delbrück scattering amplitude. This formalism includes all orders of the interaction with the external field of a nucleus by using non-perturbative electron Green's functions. The results are the Coulomb corrections to Delbrück scattering.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01292332
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    First energy and angle differential measurements of e+e−-pairs emitted by internal pair conversion of excited heavy nuclei (1998)
    Springer
    The European physical journal 1 (1998), S. 249-256 
    Details
    ISSN: 1434-601X
    Keywords: PACS:14.60.Cd Electrons (including positrons) – 23.20.En Angular distributions and correlation measurements – 23.20.Ra Internal pair production – 29.25.Rm Sources of radioactive nuclei – 29.30.Aj Charged-particle spectrometers: electric and magnetic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We present the first energy and angle resolved measurements of e+e−-pairs emitted from heavy nuclei (Z≥ 40) at rest by internal pair conversion (IPC) of transitions with energies of less than 2 MeV as well as recent theoretical results using the DWBA method, which takes full account of relativistic effects, magnetic substates and finite size of the nucleus. The 1.76 MeV E0 transition in 90Zr (90Sr source) and the 1.77 MeV M1 transition in 207Pb (207Bi source) have been investigated experimentally using the essentially improved setup at the double-ORANGE β-spectrometer of GSI. The measurements prove the capability of the setup to cleanly identify the IPC pairs in the presence of five orders of magnitude higher β− and γ background from the same source and to yield essentially background-free sum spectra despite the large background. Using the ability of the ORANGE setup to directly determine the opening angle of the e+e−–pairs (Θe+e−), the angular correlation of the emitted pairs was measured within the range covered experimentally (40°≤Θe+e−≤ 180°). In the 90Zr case the correlation could be deduced for a wide range of energy differences E Δ of the pairs (−530 keV ≤E Δ≤ 530 keV). The 90Zr results are in good agreement with recent theory. The angular correlation deduced for the M1 transition in 207Pb is in strong disagreement with theoretical predictions derived within the Born approximation and shows almost isotropic character. This is again in agreement with the new theoretical results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100500050058
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  • 5
    Electronic Resource
    Electronic Resource
    Corrections to the wave function and the hyperfine structure in exotic atoms (1998)
    Springer
    The European physical journal 2 (1998), S. 209-215 
    Details
    ISSN: 1434-6079
    Keywords: PACS. 12.20.Ds Specific calculations - 31.30.Jv Relativistic and quantum electrodynamic effects in atoms and molecules - 36.10.Dr Positronium, muonium, muonic atoms and molecules
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We present an analytical evaluation of radiative corrections in exotic atoms induced by the one-loop electronic vacuum polarization. We evaluate corrections to the energy levels, to the wave function (at the origin) and to the hyperfine structure. We treat all corrections analytically within a non-relativistic approximation. Agreement is found with a few available numerical results. The analytical treatment allows to determine the asymptotic forms of the corrections in the limit of a small atomic radius, which for the atomic systems considered corresponds to a large mass of the constituent particle as compared to the electron mass. The asymptotics can be verified using the effective charge approach.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100530050133
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    The influence of nuclear structure on the Lamb shift in hydrogenlike heavy atoms (1997)
    Springer
    Hyperfine interactions 108 (1997), S. 19-27 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We evaluate and list the various contributions to the Lamb shift in hydrogenlike heavy atoms which arise from parameters describing shape, size and structure of the nucleus. We compare these contributions with those obtained from quantum electrodynamics. It is found that in heavy nuclei, nuclear contributions depending on experimental parameters and nuclear models are of the same size as QED contributions of order a2. Therefore, in these systems the theoretical predictions for binding energies are limited by the exact knowledge of the nuclear parameters. In addition, we tabulate all corrections contributing to the 1s1/2 Lamb shift in hydrogenlike Pb and U.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1012617519654
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    Paper (German National Licenses)
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