Abstract
Soft photons inside hadronic jets converted in front of the DELPHI main tracker (TPC) in events of qq̄ disintegrations of the Z0 were studied in the kinematic range 0.2<Eγ<1 GeV and transverse momentum with respect to the closest jet direction pT<80 MeV/c. A clear excess of photons in the experimental data as compared to the Monte Carlo predictions is observed. This excess (uncorrected for the photon detection efficiency) is (1.17±0.06±0.27)×10-3 γ/jet in the specified kinematic region, while the expected level of the inner hadronic bremsstrahlung (which is not included in the Monte Carlo) is (0.340±0.001±0.038)×10-3 γ/jet. The ratio of the excess to the predicted bremsstrahlung rate is then (3.4±0.2±0.8), which is similar in strength to the anomalous soft photon signal observed in fixed target experiments with hadronic beams.
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Abdallah, J., Abreu, P., Adam, W. et al. Evidence for an excess of soft photons in hadronic decays of Z0 . Eur. Phys. J. C 47, 273–294 (2006). https://doi.org/10.1140/epjc/s2006-02568-8
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DOI: https://doi.org/10.1140/epjc/s2006-02568-8