Influence of anomalous thresholds in electron-positron annihilation into hadrons: The e+e? → ?ππ cross section |
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| Authors: | G Kramer G Schierholz K Sundermeyer |
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| Institution: | II. Institut für Theoretische Physik der Universität, Hamburg, Germany;CERN, Geneva, The Netherlands;Gesamthochschule Wuppertal, Fachbereich Physik, Wuppertal, Germany |
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| Abstract: | We calculate the cross section for e+e? → ?ππ on the basis of partial-wave dispersion relations in the ππ channel taking proper account of anomalous singularity contributions. The appearance of anomalous thresholds is due to the fact that the vertex γV?(ππ) becomes internally unstable as the virtual photon mass is increased. Reasonable agreement with existing data is found. The anomalous singularity contributions provide by far the dominant part of the cross section which is a warning to using naive vector dominance extrapolations in estimating the electron-positron cross section. |
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